Datasheet AD8276, AD8277 Datasheet (ANALOG DEVICES)

Low Power, Wide Supply Range, Low Cost

FEATURES

Wide input range beyond supplies
Rugged input overvoltage protection
Low supply current: 200 μA maximum per channel
Low power dissipation: 0.5 mW at V
Bandwidth: 550 kHz
CMRR: 86 dB minimum, dc to 10 kHz
Low offset voltage drift: ±2 μV/°C maximum (B Grade)
Low gain drift: 1 ppm/°C maximum (B Grade)
Enhanced slew rate: 1.1 V/μs
Wide power supply range:

Single supply: 2 V to 36 V
Dual supplies: ±2 V to ±18 V

APPLICATIONS

Voltage measurement and monitoring
Current measurement and monitoring
Differential output instrumentation amplifier
Portable, battery-powered equipment
Test and measurement

GENERAL DESCRIPTION

The AD8276/AD8277 are general-purpose, unity-gain difference
amplifiers intended for precision signal conditioning in power
critical applications that require both high performance and low
power. They provide exceptional common-mode rejection ratio
(86 dB) and high bandwidth while amplifying signals well beyond
the supply rails. The on-chip resistors are laser-trimmed for
excellent gain accuracy and high CMRR. They also have extremely
low gain drift vs. temperature.

The common-mode range of the amplifiers extends to almost
double the supply voltage, making these amplifiers ideal for single­supply applications that require a high common-mode voltage
range. The internal resistors and ESD circuitry at the inputs also
provide overvoltage protection to the op amps.

The AD8276/AD8277 are unity-gain stable. While they are
optimized for use as difference amplifiers, they can also be
connected in high precision, single-ended configurations with
G = −1, +1, +2. The AD8276/AD8277 provide an integrated
precision solution that has smaller size, lower cost, and better
performance than a discrete alternative.

The AD8276/AD8277 operate on single supplies (2.0 V to 36 V)
or dual supplies (±2 V to ±18 V). The maximum quiescent
supply current is 200 A per channel, which is ideal for battery­operated and portable systems.

= 2.5 V

S

Unity-Gain Difference Amplifiers

AD8276/AD8277

FUNCTIONAL BLOCK DIAGRAM

+VS

7

40kΩ 40kΩ

2

–IN

40kΩ

3 1

+IN

Figure 1. AD8276

40kΩ 40kΩ

2

–INA

40kΩ

3 14

+INA

40kΩ 40kΩ

6

–INB

40kΩ

5 8

+INB

Figure 2. AD8277

Table 1. Difference Amplifiers by Category

Low
Distortion

High
Voltage

AD8270 AD628 AD8202 (U) AD8276
AD8271 AD629 AD8203 (U) AD8277
AD8273 AD8205 (B) AD8278
AD8274 AD8206 (B)
AMP03 AD8216 (B)

1

U = unidirectional, B = bidirectional.

The AD8276 is available in the space-saving 8-lead MSOP and
SOIC packages, and the AD8277 is offered in a 14-lead SOIC
package. Both are specified for performance over the industrial
temperature range of −40°C to +85°C and are fully RoHS
compliant.

AD8276

4

–VS

+VS

11

AD8277

4

–VS

Current
Sensing

5

SENSE

6

OUT

40kΩ

40kΩ

40kΩ

REF

07692-001

12

SENSEA

13

OUTA

REFA

10

SENSEB

9

OUTB

REFB

07692-052

1

Low Power

Rev. B

Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
rights of third parties that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarks and registered trademarks are the property of their respective owners.

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: [phone] www.analog.com
Fax: [phone] ©2009–2010 Analog Devices, Inc. All rights reserved.

AD8276/AD8277

TABLE OF CONTENTS

Features .............................................................................................. 1

Applications ....................................................................................... 1 

General Description ......................................................................... 1

Functional Block Diagram .............................................................. 1

Revision History ............................................................................... 2

Specifications ..................................................................................... 3

Absolute Maximum Ratings ............................................................ 5

Thermal Resistance ...................................................................... 5

Maximum Power Dissipation ..................................................... 5

Short-Circuit Current .................................................................. 5

ESD Caution .................................................................................. 5

Pin Configurations and Function Descriptions ........................... 6

Typical Performance Characteristics ............................................. 8

Theory of Operation ...................................................................... 14

Circuit Information .................................................................... 14

Driving the AD8276/AD8277 .................................................. 14

Input Voltage Range ................................................................... 14

Power Supplies ............................................................................ 15

Applications Information .............................................................. 16

Configurations ............................................................................ 16 

Differential Output .................................................................... 16

Current Source ............................................................................ 17

Voltage and Current Monitoring .............................................. 17

Instrumentation Amplifier........................................................ 18

RTD .............................................................................................. 18 

Outline Dimensions ....................................................................... 19

Ordering Guide .......................................................................... 20

REVISION HISTORY

4/10—Rev. A to Rev. B

Changes to Figure 53 ...................................................................... 18

Updated Outline Dimensions ....................................................... 19

7/09—Rev. 0 to Rev. A

Added AD8277 ................................................................... Universal

Changes to Features Section............................................................ 1

Changes to General Description Section ...................................... 1

Added Figure 2; Renumbered Sequentially .................................. 1

Changes to Specifications Section .................................................. 3

Changes to Figure 3 and Table 5 ..................................................... 5

Added Figure 5 and Table 7; Renumbered Sequentially ............. 7

Changes to Figure 10 ........................................................................ 8

Changes to Figure 34 ...................................................................... 12

Added Figure 36 ............................................................................. 13

Changes to Input Voltage Range Section .................................... 14

Changes to Power Supplies Section and Added Figure 40 ........ 15

Added to Figure 40 ......................................................................... 15

Changes to Differential Output Section ...................................... 16

Added Figure 47 and Changes to Current Source Section ....... 17

Added Voltage and Current Monitoring Section and Figure 49..... 17

Moved Instrumentation Amplifier Section and Added RTD

Section ........................................................................................................ 18

Changes to Ordering Guide .......................................................... 20

5/09—Revision 0: Initial Version

Rev. B | Page 2 of 20

AD8276/AD8277

SPECIFICATIONS

VS = ±5 V to ±15 V, V
otherwise noted.

Table 2.

G = 1
Grade B Grade A
Parameter Conditions Min Typ Max Min Typ Max Unit

INPUT CHARACTERISTICS

System Offset1 100 200 100 500 µV

vs. Temperature TA = −40°C to +85°C 200 500 µV
Average Temperature

Coefficient

vs. Power Supply VS = ±5 V to ±18 V 5 10 µV/V

Common-Mode Rejection

Ratio (RTI)
Input Voltage Range2 −2(VS + 0.1) +2(VS − 1.5) −2(VS + 0.1) +2(VS − 1.5) V
Impedance3

Differential 80 80 kΩ

Common Mode 40 40 kΩ

DYNAMIC PERFORMANCE

Bandwidth 550 550 kHz
Slew Rate 0.9 1.1 0.9 1.1 V/µs
Settling Time to 0.01%

Settling Time to 0.001% 16 16 µs
Channel Separation f = 1 kHz 130 130 dB

GAIN

Gain Error 0.005 0.02 0.01 0.05 %
Gain Drift TA = −40°C to +85°C 1 5 ppm/°C
Gain Nonlinearity V

OUTPUT CHARACTERISTICS

Output Voltage Swing4

Short-Circuit Current Limit ±15 ±15 mA
Capacitive Load Drive 200 200 pF

NOISE5

Output Voltage Noise f = 0.1 Hz to 10 Hz 2 2 V p-p
f = 1 kHz 65 70 65 70 nV/√Hz

POWER SUPPLY

Supply Current6 200 200 A

vs. Temperature TA = −40°C to +85°C 250 250 A
Operating Voltage Range7 ±2 ±18 ±2 ±18 V

TEMPERATURE RANGE

Operating Range −40 +125 −40 +125 °C

1

Includes input bias and offset current errors, RTO (referred to output).

2

The input voltage range may also be limited by absolute maximum input voltage or by the output swing. See the section in the The

Operation

3

Internal resistors are trimmed to be ratio matched and have ±20% absolute accuracy.

4

Output voltage swing varies with supply voltage and temperature. See Figur through for details. e 18 Figure 21

5

Includes amplifier voltage and current noise, as well as noise from internal resistors.

6

Supply current varies with supply voltage and temperature. See Figure and for details. 22 Figure 24

7

Unbalanced dual supplies can be used, such as −VS = −0.5 V and +VS = +2 V. The positive supply rail must be at least 2 V above the negative supply and reference

voltage.

section for details.

= 0 V, TA = 25°C, RL = 10 k connected to ground, G = 1 difference amplifier configuration, unless

REF

T

= −40°C to +85°C 0.5 2 2 5 µV/°C

A

VS = ±15 V, VCM = ±27 V,

= 0 Ω 86 80 dB

R

S

10 V step on output,

= 100 pF

C

L

= 20 V p-p 5 10 ppm

OUT

= ±15 V, RL = 10 kΩ,

V

S

= −40°C to +85°C −VS + 0.2 +VS − 0.2 −VS + 0.2 +VS − 0.2 V

T

A

15 15 µs

Input Voltage Range ory of

Rev. B | Page 3 of 20

AD8276/AD8277

VS = +2.7 V to <±5 V, V
otherwise noted.

Table 3.

G = 1
Grade B Grade A
Parameter Conditions Min Typ Max Min Typ Max Unit

INPUT CHARACTERISTICS

System Offset1 100 200 100 500 µV

vs. Temperature TA = −40°C to +85°C 200 500 µV
Average Temperature

Coefficient

vs. Power Supply VS = ±5 V to ±18 V 5 10 µV/V

Common-Mode Rejection

Ratio (RTI)

Input Voltage Range2 −2(VS + 0.1) +2( VS − 1.5) −2(VS + 0.1) +2(VS − 1.5) V
Impedance3

Differential 80 80 kΩ
Common Mode 40 40 kΩ

DYNAMIC PERFORMANCE

Bandwidth 450 450 kHz
Slew Rate 1.0 1.0 V/µs
Settling Time to 0.01%

Channel Separation f = 1 kHz 130 130 dB

GAIN

Gain Error 0.005 0.02 0.01 0.05 %
Gain Drift TA = −40°C to +85°C 1 5 ppm/°C

OUTPUT CHARACTERISTICS

Output Swing4

Short-Circuit Current

Limit

Capacitive Load Drive 200 200 pF

NOISE5

Output Voltage Noise f = 0.1 Hz to 10 Hz 2 2 V p-p
f = 1 kHz 65 65 nV/√Hz

POWER SUPPLY

Supply Current6 T
Operating Voltage

Range

TEMPERATURE RANGE

Operating Range −40 +125 −40 +125 °C

1

Includes input bias and offset current errors, RTO (referred to output).

2

The input voltage range may also be limited by absolute maximum input voltage or by the output swing. See the section in the

section for details.

3

Internal resistors are trimmed to be ratio matched and have ±20% absolute accuracy.

4

Output voltage swing varies with supply voltage and temperature. See Figur through for details. e 18 Figure 21

5

Includes amplifier voltage and current noise, as well as noise from internal resistors.

6

Supply current varies with supply voltage and temperature. See Figure and for details. 23 Figure 24

= midsupply, TA = 25°C, RL = 10 k connected to midsupply, G = 1 difference amplifier configuration, unless

REF

= −40°C to +85°C 0.5 2 2 5 µV/°C

T

A

VS = 2.7 V, VCM = 0 V
to 2.4 V, R

= ±5 V, VCM = −10 V

V

S

to +7 V, R

= 0 Ω

S

= 0 Ω 86 80 dB

S

8 V step on output,

= 100 pF, VS = 10 V

C

L

= 10 kΩ ,

R

L

= −40°C to +85°C −VS + 0.1 +VS − 0.15 −VS + 0.1 +VS − 0.15 V

T

A

86 80 dB

5 5 µs

±10 ±10 mA

= −40°C to +85°C 200 200 A

A

2.0 36 2.0 36 V

Input Voltage Range Theory of Operation

Rev. B | Page 4 of 20

AD8276/AD8277

ABSOLUTE MAXIMUM RATINGS

2.0

Table 4.

Parameter Rating

Supply Voltage ±18 V
Maximum Voltage at Any Input Pin −VS + 40 V
Minimum Voltage at Any Input Pin +VS − 40 V
Storage Temperature Range −65°C to +150°C
Specified Temperature Range −40°C to +85°C
Package Glass Transition Temperature (TG) 150°C

Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only; functional operation of the device at these or any
other conditions above those indicated in the operational
section of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability.

THERMAL RESISTANCE

The θJA values in Tabl e 5 assume a 4-layer JEDEC standard
board with zero airflow.

Table 5.

Package Type θJA Unit

8-Lead MSOP 135 °C/W
8-Lead SOIC 121 °C/W
14-Lead SOIC 105 °C/W

MAXIMUM POWER DISSIPATION

The maximum safe power dissipation for the AD8276/AD8277
is limited by the associated rise in junction temperature (T
the die. At approximately 150°C, which is the glass transition
temperature, the properties of the plastic change. Even temporarily
exceeding this temperature limit may change the stresses that the
package exerts on the die, permanently shifting the parametric
performance of the amplifiers. Exceeding a temperature of 150°C
for an extended period may result in a loss of functionality.

) on

J

1.6

1.2

0.8

0.4

MAXIMUM POWER DISSIPATI O N (W )

0

–50 0–25 25 50 75 100 125

Figure 3. Maximum Power Dissipation vs. Ambient Temperature

SHORT-CIRCUIT CURRENT

The AD8276/AD8277 have built-in, short-circuit protection
that limits the output current (see Figure 25 for more information).
While the short-circuit condition itself does not damage the
part, the heat generated by the condition can cause the part to
exceed its maximum junction temperature, with corresponding
negative effects on reliability. Figure 3 and Figure 25, combined
with knowledge of the supply voltages and ambient temperature of
the part, can be used to determine whether a short circuit will
cause the part to exceed its maximum junction temperature.

ESD CAUTION

14-LEAD SO IC

θ

= 105°C/W

JA

8-LEAD MSO P

θ

= 135°C/W

JA

AMBIENT TEMERATURE (°C)

TJ MAX = 150°C

8-LEAD SOIC

θ

= 121°C/W

JA

07692-002

Rev. B | Page 5 of 20

AD8276/AD8277

PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS

REF

1

AD8276

2

–IN

TOP VIEW

+IN

3

(Not to S cale)

–VS

4

NC = NO CONNECT

Figure 4. AD8276 8-Lead MSOP Pin Configuration

Table 6. AD8276 Pin Function Descriptions

Pin No. Mnemonic Description

1 REF Reference Voltage Input.
2 −IN Inverting Input.
3 +IN Noninverting Input.
4 −VS Negative Supply.
5 SENSE Sense Terminal.
6 OUT Output.
7 +VS Positive Supply.
8 NC No Connect.

8
7
6
5

NC
+VS
OUT
SENSE

REF

1

AD8276

–IN

2

TOP VIEW

+IN

3

(Not to Scale)

4

–VS

7692-003

NC = NO CONNECT

8
7
6
5

NC
+VS
OUT
SENSE

7692-004

Figure 5. AD8276 8-Lead SOIC Pin Configuration

Rev. B | Page 6 of 20

AD8276/AD8277

NC

1
2

–INA

3

+INA

–VS

4

+INB

5
6

–INB

7

NC

NC = NO CONNECT

Figure 6. AD8277 14-Lead SOIC Pin Configuration

Table 7. AD8277 Pin Function Descriptions

Pin No. Mnemonic Description

1 NC No Connect.
2 −INA Channel A Inverting Input.
3 +INA Channel A Noninverting Input.
4 −VS Negative Supply.
5 +INB Channel B Noninverting Input.
6 −INB Channel B Inverting Input.
7 NC No Connect.
8 REFB Channel B Reference Voltage Input.
9 OUTB Channel B Output.
10 SENSEB Channel B Sense Terminal.
11 +VS Positive Supply.
12 SENSEA Channel A Sense Terminal.
13 OUTA Channel A Output.
14 REFA Channel A Reference Voltage Input.

AD8277

TOP VIEW

(Not to Scale)

14
13
12

11

10

9
8

REFA
OUTA
SENSEA
+VS
SENSEB
OUTB
REFB

07692-053

Rev. B | Page 7 of 20

AD8276/AD8277

TYPICAL PERFORMANCE CHARACTERISTICS

VS = ±15 V, TA = 25°C, RL = 10 kΩ connected to ground, G = 1 difference amplifier configuration, unless otherwise noted.

N = 2042
MEAN = –2.28

600

SD = 32.7

500

400

300

NUMBER OF HITS

200

100

0
–300 –200 –100 0 100 200 300

SYSTEM OFFS ET VOLTAGE (µV )

Figure 7. Distribution of Typical System Offset Voltage

N = 2040
MEAN = –0.87

400

SD = 16.2

300

200

NUMBER OF HITS

100

0

–90 –60 –30 0 30 60 90

CMRR (µV/V)

Figure 8. Distribution of Typical Common-Mode Rejection

4

07692-005

07692-006

80

60

40

20

0

–20

–40

SYSTEM OFF SET (µV)

–60

–80

–100

–50 –35 –20 –5 10 25 40 55 70 85

TEMPERATURE ( °C)

Figure 10. System Offset vs. Temperature, Normalized at 25°C

20

15

10

5

0

–5

–10

GAIN ERROR (µV/V)

–15

–20

–25

REPRESENTATIVE DATA

–30

–50 –35 –20 –5 10 25 40 55 70 85 90

TEMPERATURE (° C)

Figure 11. Gain Error vs. Temperature, Normalized at 25°C

10

07692-008

07692-009

2

0

–2

CMRR (µV/V)

–4

–6

REPRESENTATIVE DATA

–8

–50 –35 –20 –5 10 25 40 55 70 85 90

TEMPERATURE (° C)

Figure 9. CMRR vs. Temperature, Normalized at 25°C

07692-007

Rev. B | Page 8 of 20

0

–10

–20

GAIN (dB)

–30

–40

–50

100 10M1M100k10k1k

FREQUENCY (Hz)

Figure 12. Gain vs. Frequency, VS = ±15 V, +2.7 V

VS = ±15V

VS = +2.7V

07692-010

AD8276/AD8277

V

120

100

80

60

CMRR (dB)

40

20

VS = ±15V

8

6

4

2

0

–2

COMMON-MODE VOLTAGE (V)

–4

V

S

= 2.7V

V

VS = 5V

= MIDSUPPLY

REF

0

11M

FREQUENCY (Hz)

100k10k1k10010

07692-011

Figure 13. CMRR vs. Frequency

–6

–0.5 0.5 1.5 2.5 3.5 4.5 5.5

Figure 16. Input Common-Mode Voltage vs. Output Voltage,

5 V and 2.7 V Supplies, V

120

100

PSRR (dB)

80

60

40

20

0

11M100k10k1k10010

FREQUENCY (Hz)

–PSRR

+PSRR

Figure 14. PSRR vs. Frequency

30

VS = ±15V

20

10

VS = ±5V

OUTPUT VOLTAGE (V)

COMMON-MODE VOLTAGE (V)

0

–10

–20

–30

–20 20151050–5–10–15

Figure 15. Input Common-Mode Voltage vs. Output Voltage,

07692-012

07692-013

8

6

4

2

0

COMMON-MODE VOLTAGE (V)

–2

–4

–0.5 0.5 1.5 2.5 3.5 4.5 5.5

Figure 17. Input Common-Mode Voltage vs. Output Voltage,

+

S

–0.1
–0.2
–0.3
–0.4

+0.4
+0.3

OUTPUT VO LTAGE SW ING (V)

+0.2

REFERRED TO S UPPLY VOL TAGES

+0.1

–V

S

2116141210864

Figure 18. Output Voltage Swing vs. Supply Voltage Per Channel and

±15 V and ±5 V Supplies

OUTPUT VOLTAGE (V)

REF

VS = 5V

V

= 2.7V

S

OUTPUT VOLTAGE (V)

5 V and 2.7 V Supplies, V

SUPPLY VOLTAGE (±VS)

Temperature, R

= 10 kΩ

L

= Midsupply

= 0 V

REF

V

= 0V

REF

TA = –40°C
TA = +25°C
TA = +85°C
TA = +125°C

07692-014

07692-015

8

07692-016

Rev. B | Page 9 of 20

AD8276/AD8277

V

V

V

+

S

–0.2
–0.4
–0.6
–0.8
–1.0
–1.2

+1.2
+1.0
+0.8

OUTPUT VOLTAGE SWING (V)

+0.6

REFERRED TO SUPPLY VOLTAGES

+0.4
+0.2

–V

S

21816141210864

SUPPLY VOLTAGE (±VS)

TA = –40°C
TA = +25°C
TA = +85°C
TA = +125°C

Figure 19. Output Voltage Swing vs. Supply Voltage Per Channel and

Temperature, R

+

S

= 2 kΩ

L

07692-017

180

170

160

150

140

SUPPLY CURRENT ( µ A)

130

120

01161412108642

SUPPLY VOLTAGE (±V)

8

Figure 22. Supply Current Per Channel vs. Dual Supply Voltage, VIN = 0 V

180

07692-020

–4

–8

TA = –40°C
TA = +25°C
TA = +85°C
TA = +125°C

+8

OUTPUT VOLTAGE SWING (V)

+4

REFERRED TO SUPPLY VOLTAGES

–V

S

1k 100k10k

LOAD RESISTANCE (Ω)

07692-018

Figure 20. Output Voltage Swing vs. RL and Temperature, VS = ±15 V

+

S

–0.5

–1.0

–1.5

–2.0

+2.0

+1.5

OUTPUT VOLTAGE SWING (V)

+1.0

REFERRED TO SUPPLY VOLTAGES

+0.5
–V

S

01987654321 0

Figure 21. Output Voltage Swing vs. I

OUTPUT CURRENT (mA)

and Temperature, VS = ±15 V

OUT

TA = –40°C
TA = +25°C
TA = +85°C
TA = +125°C

07692-019

170

160

150

140

SUPPLY CURRENT ( µ A)

130

120

043530252015105

Figure 23. Supply Current Per Channel vs. Single-Supply Voltage, VIN = 0 V,

250

200

150

VS = ±15V

100

SUPPLY CURRENT ( µ A)

50

0

–50 –30 –10 10 30 50 70 90 110 130

Figure 24. Supply Current Per Channel vs. Temperature

V

= +2.7V

S

SUPPLY VOLTAGE (V)

V

= 0 V

REF

TEMPERATURE (° C)

V

= MIDSUPPLY

REF

0

07692-021

07692-022

Rev. B | Page 10 of 20

AD8276/AD8277

V

30

25

20

15

10

5

0

–5

–10

SHORT-CIRCUI T CURRENT (mA)

–15

–20

–50 –30 –10 10 30 50 70 90 110 130

I

SHORT+

I

SHORT–

TEMPERATURE (° C)

Figure 25. Short-Circuit Current Per Channel vs. Temperature

1.4

1.2

1.0

0.8

0.6

SLEW RATE (V/µ s)

0.4

–SR

+SR

07692-023

5V/DIV

11.24 µs TO 0 .01%

13.84µs TO 0.001%

0.002%/DIV

40µs/DIV

TIME (µs)

7692-026

Figure 28. Large-Signal Pulse Response and Settling Time, 10 V Step,

= ±15 V

V

S

1V/DIV

4.34 µs TO 0.01%

5.12µs TO 0.001%

0.002%/DIV

0.2

0

–50 –30 –10 10 30 50 70 90 110 130

TEMPERATURE (° C)

Figure 26. Slew Rate vs. Temperature, VIN = 20 V p-p, 1 kHz

8

6

4

2

0

–2

–4

NONLINEARITY (2ppm/ DI V)

–6

–8

–10–8–6–4–20246810

OUTPUT VOLTAGE (V)

Figure 27. Gain Nonlinearity, VS = ±15 V, RL ≥ 2 kΩ

40µs/DIV

TIME (µs)

07692-024

7692-027

Figure 29. Large-Signal Pulse Response and Settling Time, 2 V Step,

V

= 2.7 V

S

2V/DI

10µs/DIV

07692-025

07692-028

Figure 30. Large-Signal Step Response

Rev. B | Page 11 of 20

AD8276/AD8277

V
V

30

25

20

VS = ±15V

40

35

30

25

±2V

±5V

15

V

= ±5V

S

10

OUTPUT VOLTAGE (V p-p)

5

0

100 1k 10k 100k 1M

Figure 31. Maximum Output Voltage vs. Frequency, V

5.0
VS = 5V

4.5

4.0

3.5

3.0

2.5

= 2.7V

V

S

2.0

1.5

OUTPUT VOLTAGE (V p-p)

1.0

0.5

0

100 1k 10k 100k 1M

FREQUENCY (Hz)

FREQUENCY (Hz)

= ±15 V, ±5 V

S

Figure 32. Maximum Output Voltage vs. Frequency, VS = 5 V, 2.7 V

20

15

OVERSHOOT (%)

10

5

0

100 150 200 250 300 350 400

07692-029

CAPACITIVE LOAD (pF)

±15V

±18V

07692-051

Figure 34. Small-Signal Overshoot vs. Capacitive Load, RL ≥ 2 kΩ

1k

100

NOISE (nV/ Hz)

10

0.1 100k10k1k100101

07692-030

FREQUENCY (Hz)

07692-034

Figure 35. Voltage Noise Density vs. Frequency

20mV/DI

CL = 100pF

C

= 200pF

L

C

= 300pF

L

C

= 470pF

L

40µs/DIV

Figure 33. Small-Signal Step Response for Various Capacitive Loads

07692-050

1µV/DI

1s/DIV

07692-035

Figure 36. 0.1 Hz to 10 Hz Voltage Noise

Rev. B | Page 12 of 20

AD8276/AD8277

160

NO LOAD

140

10kΩ LOAD

120

2kΩ LOAD

100

1kΩ LOAD

80

60

40

CHANNEL SEPARATIO N (dB)

20

0

1110k1k10010

FREQUENCY (Hz)

00k

07692-055

Figure 37. Channel Separation

Rev. B | Page 13 of 20

AD8276/AD8277

THEORY OF OPERATION

CIRCUIT INFORMATION

Each channel of the AD8276/AD8277 consists of a low power, low
noise op amp and four laser-trimmed on-chip resistors. These
resistors can be externally connected to make a variety of amplifier
configurations, including difference, noninverting, and inverting
configurations. Taking advantage of the integrated resistors of
the AD8276/AD8277 provides the designer with several benefits
over a discrete design, including smaller size, lower cost, and
better ac and dc performance.

+VS

7

AD8276

40kΩ 40kΩ

2

IN–

40kΩ

3 1

IN+

4

–VS

Figure 38. Functional Block Diagram

DC Performance

Much of the dc performance of op amp circuits depends on the
accuracy of the surrounding resistors. Using superposition to
analyze a typical difference amplifier circuit, as is shown in
Figure 39, the output voltage is found to be

OUT

⎛
⎜

=

VV

⎜
⎝

⎞

R2

⎛

⎟

+

1

⎜

⎟

+

R2R1

⎝

⎠

This equation demonstrates that the gain accuracy and common­mode rejection ratio of the AD8276/AD8277 is determined
primarily by the matching of resistor ratios. Even a 0.1% mismatch
in one resistor degrades the CMRR to 66 dB for a G = 1 difference
amplifier.

The difference amplifier output voltage equation can be reduced to

R4

()

V

OUT

R3

−=

+

VV

IIN

−

N

as long as the following ratio of the resistors is tightly matched:

R4

R2

R1

=

R3

The resistors on the AD8276/AD8277 are laser trimmed to match
accurately. As a result, the AD8276/AD8277 provide superior
performance over a discrete solution, enabling better CMRR,
gain accuracy, and gain drift, even over a wide temperature range.

40kΩ

R4
R3

5

SENSE

6

OUT

REF

07692-031

R4

⎞

⎞
⎟
⎠

⎛

−

V

⎟

⎜

−+

ININ

R3

⎠

⎝

AC Performance

Component sizes and trace lengths are much smaller in an IC
than on a PCB, so the corresponding parasitic elements are also
smaller. This results in better ac performance of the AD8276/
AD8277. For example, the positive and negative input terminals
of the AD8276/AD8277 op amps are intentionally not pinned
out. By not connecting these nodes to the traces on the PCB, the
capacitance remains low, resulting in improved loop stability
and excellent common-mode rejection over frequency.

DRIVING THE AD8276/AD8277

Care should be taken to drive the AD8276/AD8277 with a low
impedance source: for example, another amplifier. Source
resistance of even a few kilohms (kΩ) can unbalance the resistor
ratios and, therefore, significantly degrade the gain accuracy and
common-mode rejection of the AD8276/AD8277. Because all
configurations present several kilohms of input resistance, the
AD8276/AD8277 do not require a high current drive from the
source and so are easy to drive.

INPUT VOLTAGE RANGE

The AD8276/AD8277 are able to measure input voltages beyond
the supply rails. The internal resistors divide down the voltage
before it reaches the internal op amp and provide protection to
the op amp inputs. Figure 39 shows an example of how the
voltage division works in a difference amplifier configuration.
For the AD8276/AD8277 to measure correctly, the input
voltages at the input nodes of the internal op amp must stay
below 1.5 V of the positive supply rail and can exceed the
negative supply rail by 0.1 V. Refer to the Power Supplies section
for more details.

R2

(V

)

IN+

R1 + R2

R3

V

IN–

R1

V

IN+

Figure 39. Voltage Division in the Difference Amplifier Configuration

R2

The AD8276/AD8277 have integrated ESD diodes at the inputs
that provide overvoltage protection. This feature simplifies
system design by eliminating the need for additional external
protection circuitry, and enables a more robust system.

The voltages at any of the inputs of the parts can safely range
from +V

− 40 V up to −VS + 40 V. For example, on ±10 V

S

supplies, input voltages can go as high as ±30 V. Care should be
taken to not exceed the +V

− 40 V to −VS + 40 V input limits

S

to avoid risking damage to the parts.

R2

R1 + R2

R4

(V

)

IN+

7692-033

Rev. B | Page 14 of 20

AD8276/AD8277

POWER SUPPLIES

The AD8276/AD8277 operate extremely well over a very wide
range of supply voltages. They can operate on a single supply as
low as 2 V and as high as 36 V, under appropriate setup conditions.

For best performance, the user must exercise care that the setup
conditions ensure that the internal op amp is biased correctly.
The internal input terminals of the op amp must have sufficient
voltage headroom to operate properly. Proper operation of the
part requires at least 1.5 V between the positive supply rail and
the op amp input terminals. This relationship is expressed in
the following equation:

R1

+

R2R1

REF

VV

For example, when operating on a +V
V

= 0 V, it can be seen from Figure 40 that the input terminals

REF

of the op amp are biased at 0 V, allowing more than the required

1.5 V headroom. However, if V
the input terminals of the op amp are biased at 0.5 V, barely
allowing the required 1.5 V headroom. This setup does not allow
any practical voltage swing on the non inverting input. Therefore,
the user needs to increase the supply voltage or decrease V
restore proper operation.

V5.1−+<

S

= 2 V single supply and

S

= 1 V under the same conditions,

REF

REF

to

The AD8276/AD8277 are typically specified at single- and dual­supplies, but they can be used with unbalanced supplies, as well;
for example, −V

= −5 V, +VS = 20 V. The difference between the

S

two supplies must be kept below 36 V. The positive supply rail
must be at least 2 V above the negative supply and reference
voltage.

R1

(V

)

REF

R1 + R2

R3

R1

R2

V

REF

Figure 40. Ensure Sufficient Voltage Headroom on the Internal Op Amp

R1

R1 + R2

Inputs

R4

(V

)

REF

07692-032

Use a stable dc voltage to power the AD8276/AD8277. Noise on
the supply pins can adversely affect performance. Place a bypass
capacitor of 0.1 µF between each supply pin and ground, as
close as possible to each supply pin. Use a tantalum capacitor
of 10 µF between each supply and ground. It can be farther
away from the supply pins and, typically, it can be shared by
other precision integrated circuits.

Rev. B | Page 15 of 20

AD8276/AD8277

V

V

A

V

APPLICATIONS INFORMATION

CONFIGURATIONS

The AD8276/AD8277 can be configured in several ways (see
Figure 42 to Figure 46). All of these configurations have excellent
gain accuracy and gain drift because they rely on the internal
matched resistors. Note that Figure 43 shows the AD8276/AD8277
as difference amplifiers with a midsupply reference voltage at
the noninverting input. This allows the AD8276/AD8277 to be
used as a level shifter, which is appropriate in single-supply
applications that are referenced to midsupply.

As with the other inputs, the reference must be driven with a
low impedance source to maintain the internal resistor ratio. An
example using the low power, low noise OP1177 as a reference
is shown in Figure 41.

INCORRECT

AD8276

REF

V

Figure 41. Driving the Reference Pin

40kΩ

2

–IN

40kΩ 40kΩ

3

+IN

V

= V

− V

OUT

IN+

IN−

Figure 42. Difference Amplifier, Gain = 1

− V

40kΩ

IN−

40kΩ

2

–IN

40kΩ 40kΩ

3

+IN

= V

OUT

IN+

Figure 43. Difference Amplifier, Gain = 1, Referenced to Midsupply

V

40kΩ

CORRECT

+

OP1177

–

5

6

1

5

OUT

6

1

= MIDSUPPLY

V

REF

AD8276

REF

OUT

7692-037

07692-038

07692-039

40kΩ

2

IN

40kΩ

1

40kΩ

3

V

= –V

OUT

Figure 44. Inverting Amplifier, Gain = −1

40kΩ

2

40kΩ 40kΩ

3

IN

= V

OUT

IN

Figure 45. Noninverting Amplifier, Gain = 1

40kΩ

25

40kΩ

1

IN

40kΩ

3

= 2V

V

OUT

IN

Figure 46. Noninverting Amplifier, Gain = 2

DIFFERENTIAL OUTPUT

Certain systems require a differential signal for better perfor­mance, such as the inputs to differential analog-to-digital
converters. Figure 47 shows how the AD8276/AD8277 can
be used to convert a single-ended output from an AD8226
instrumentation amplifier into a differential signal. The internal
matched resistors of the AD8276 at the inverting input maximize
gain accuracy while generating a differential signal. The resistors at
the noninverting input can be used as a divider to set and track
the common-mode voltage accurately to midsupply, especially
when running on a single supply or in an environment where
the supply fluctuates. The resistors at the noninverting input
can also be shorted and set to any appropriate bias voltage. Note
that the V
the AD8276 because it is not pinned out.

= VCM node indicated in Figure 47 is internal to

BIAS

+IN

–IN

D8226

V

REF

IN

R

R

40kΩ

40kΩ

40kΩ

AD8276

5

OUT

6

7692-040

5

OUT

6

1

7692-041

OUT

6

07692-042

+

S

R

R

V

BIAS

= V

+OUT

CM

VS–

–OUT

07692-043

Figure 47. Differential Output With Supply Tracking on Common-Mode

Voltage Reference

Rev. B | Page 16 of 20

AD8276/AD8277

V

The differential output voltage and common-mode voltage of
the AD8226 is shown in the following equations:

V

V

= V

DIFF_OUT

= (VS+ − VS−)/2 = V

CM

+OUT

− V

−OUT

= Gain

BIAS

AD8226

× (V

+IN

– V

−IN

)

Refer to the AD8226 data sheet for additional information.

+VS

11

AD8277

40kΩ 40kΩ

–IN

+IN

2

40kΩ

3 14

40kΩ 40kΩ

6

40kΩ

5 8

40kΩ

40kΩ

4

–VS

12

13

10

9

+OUT

–OUT

7692-056

Figure 48. AD8277 Differential Output Configuration

The two difference amplifiers of the AD8277 can be configured
to provide a differential output, as shown in Figure 48. This
differential output configuration is suitable for various applications,
such as strain gage excitation and single-ended-to-differential
conversion. The differential output voltage has a gain of 2 as
shown in the following equation:

V

DIFF_OUT

= V

+OUT

− V

−OUT

= 2 × (V

+IN

– V

−IN

)

CURRENT SOURCE

The AD8276 difference amplifier can be implemented as part
of a voltage-to-current converter or a precision constant current
source as shown in Figure 49. Using an integrated precision
solution such as the AD8276 provides several advantages over
a discrete solution, including space-saving, improved gain accuracy,
and temperature drift. The internal resistors are tightly matched
to minimize error and temperature drift. If the external resistors,
R1 and R2, are not well-matched, they become a significant
source of error in the system, so precision resistors are recom­mended to maintain performance. The ADR821 provides a
precision voltage reference and integrated op amp that also
reduces error in the signal chain.

The AD8276 has rail-to-rail output capability that allows higher
current outputs.

V+

1

2

3

4

REF

5

ADR821

V–

–2.5V

10

9

8

7

6

2

3

7

40kΩ

40kΩ

AD8276

4

+

40kΩ

5

6

40kΩ

1

I

= 2.5V(1/40kΩ + 1/R1)

O

R1 = R2

2N3904

R2

R1

R

LOAD

Figure 49. Constant Current Source

VOLTAGE AND CURRENT MONITORING

Voltage and current monitoring is critical in the following
applications: power line metering, power line protection, motor
control applications, and battery monitoring. The AD8276/
AD8277 can be used to monitor voltages and currents in a
system, as shown in Figure 50. As the signals monitored by the
AD8276/AD8277 rise above or drop below critical levels, a
circuit event can be triggered to correct the situation or raise
a warning.

AD8276

I

R

1

AD8276

I

R

3

I

C

AD8276

V

R

1

8:1

OP1177

AD8276

V

R

3

AD8276

V

R

C

Figure 50.Voltage and Current Monitoring in 3-Phase Power Line Protection

Using the AD8276

Figure 50 shows an example of how the AD8276 can be used to
monitor voltage and current on a 3-phase power supply. I
through I

are the currents to be monitored, and V1 through V3

3

are the voltages to be monitored on each phase. I
the common or zero lines. Couplers or transformers interface
the power lines to the front-end circuitry and provide
attenuation, isolation, and protection.

On the current monitoring side, current transformers (CTs)
step down the power-line current and isolate the front-end
circuitry from the high voltage and high current lines. Across
the inputs of each difference amplifier is a shunt resistor that
converts the coupled current into a voltage. The value of the

ADC

07692-057

1

and VC are

C

07692-046

Rev. B | Page 17 of 20

AD8276/AD8277

resistor is determined by the characteristics of the coupler or
transformer and desired input voltage ranges to the AD8276.

On the voltage monitoring side, potential transformers (PTs)
are used to provide coupling and galvanic isolation. The PTs
present a load to the power line and also step down the voltage
to a measureable level. The AD8276 helps to build a robust
system because it allows input voltages that are almost double
its supply voltage, while providing additional input protection
in the form of the integrated ESD diodes.

Not only does the AD8276 monitor the voltage and currents on
the power lines, it is able to reject very high common-mode
voltages that may appear at the inputs. The AD8276 also
performs the differential-to-single-ended conversion on the
input voltages. The 80 k differential input impedance that the
AD8276 presents is high enough that it should not load the
input signals.

I

SH

AD8276

R

SH

V

OUT

= ISH × R

SH

07692-058

Figure 51. AD8276 Monitoring Current Through a Shunt Resistor

Figure 51 shows how the AD8276 can be used to monitor the
current through a small shunt resistor. This is useful in power
critical applications such as motor control (current sense) and
battery monitoring.

INSTRUMENTATION AMPLIFIER

The AD8276/AD8277 can be used as building blocks for a low
power, low cost instrumentation amplifier. An instrumentation
amplifier provides high impedance inputs and delivers high
common-mode rejection. Combining the AD8276 with an
Analog Devices, Inc. low power amplifier (see Table 8 ) creates a
precise, power efficient voltage measurement solution suitable
for power critical systems.

–IN

R

+IN

Figure 52. Low Power Precision Instrumentation Amplifier

A1

R

F

G

R

F

A2

40kΩ

40kΩ

40kΩ

AD8276

REF

V

= (1 + 2RF/RG) (V

OUT

40kΩ

IN+

– V

V

OUT

)

IN–

07692-045

Table 8. Low Power Op Amps

Op Amp (A1, A2) Features

AD8506 Dual micropower op amp
AD8607 Precision dual micropower op amp
AD8617 Low cost CMOS micropower op amp
AD8667 Dual precision CMOS micropower op amp

It is preferable to use dual op amps for the high impedance inputs
because they have better matched performance and track each
other over temperature. The AD8276 difference amplifiers
cancel out common-mode errors from the input op amps, if
they track each other. The differential gain accuracy of the in­amp is proportional to how well the input feedback resistors
(R

) match each other. The CMRR of the in-amp increases as

F

the differential gain is increased (1 + 2R

), but a higher gain

F/RG

also reduces the common-mode voltage range. Note that dual
supplies must be used for proper operation of this configuration.

Refer to

A Designer’s Guide to Instrumentation Amplifiers for

more design ideas and considerations.

RTD

Resistive temperature detectors (RTDs) are often measured
remotely in industrial control systems. The wire lengths
needed to connect the RTD to a controller add significant
cost and resistance errors to the measurement. The AD8276
difference amplifier is effective in measuring errors caused by
wire resistance in remote 3-wire RTD systems, allowing the
user to cancel out the errors introduced by the wires. Its
excellent gain drift provides accurate measurements and stable
performance over a wide temperature range.

I

EX

R

L1

R

T

R

L2

R

L3

40kΩ

40kΩ

Figure 53. 3-Wire RTD Cable Resistance Error Measurement

40kΩ40kΩ

AD8276

V

OUT

Σ-Δ

ADC

7692-059

Rev. B | Page 18 of 20

AD8276/AD8277

OUTLINE DIMENSIONS

3.20

3.00

2.80

8

5

3.20

3.00

2.80

PIN 1

IDENTIFIER

0.95

0.85

0.75

0.15

0.05

COPLANARITY

1

0.65 BSC

0.10

COMPLIANT TO JEDEC STANDARDS MO-187-AA

Figure 54. 8-Lead Mini Small Outline Package [MSOP]

5.00(0.1968)

4.80(0.1890)

5.15

4.90

4.65

4

15° MAX

6°
0°

0.23

0.09

0.40

0.25

1.10 MAX

(RM-8)

Dimensions shown in millimeters

0.80

0.55

0.40

100709-B

4.00 (0.1574)

3.80 (0.1497)

0.25 (0.0098)

0.10 (0.0040)

COPLANARITY

0.10

CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS
(IN PARENTHESES)ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR
REFERENCE ONLYAND ARE NOT APPROPRIATE FOR USEIN DESIGN.

85

1

1.27 (0.0500)

SEATING

PLANE

COMPLIANT TO JEDEC STANDARDS MS-012-AA

BSC

6.20 (0.2441)

5.80 (0.2284)

4

1.75 (0.0688)

1.35 (0.0532)

0.51 (0.0201)

0.31 (0.0122)

8°
0°

0.25 (0.0098)

0.17 (0.0067)

0.50 (0.0196)

0.25 (0.0099)

1.27 (0.0500)

0.40 (0.0157)

45°

012407-A

Figure 55. 8-Lead Standard Small Outline Package [SOIC_N]

Narrow Body (R-8)

Dimensions shown in millimeters and (inches)

Rev. B | Page 19 of 20

AD8276/AD8277

4.00 (0.1575)

3.80 (0.1496)

0.25 (0.0098)

0.10 (0.0039)

COPLANARITY

0.10

CONTROLLING DIME NSIONS ARE IN MILLIMETERS; INCH DIMENSIONS
(IN PARENTHESES) ARE ROUNDED-OFF MILLI M E TER EQUIVALENTS FOR
REFERENCE ONLYAND ARE NOT APP ROPRIATE FOR USE IN DESIGN.

8.75 (0.3445)

8.55 (0.3366)

BSC

8

7

6.20 (0.2441)

5.80 (0.2283)

1.75 (0.0689)

1.35 (0.0531)

SEATING
PLANE

0.25 (0.0098)

0.17 (0.0067)

14

1

1.27 (0.0500)

0.51 (0.0201)

0.31 (0.0122)

COMPLIANT TO JEDEC STANDARDS MS-012-AB

0.50 (0.0197)

0.25 (0.0098)

8°
0°

1.27 (0.0500)

0.40 (0.0157)

45°

060606-A

Figure 56. 14-Lead Standard Small Outline Package [SOIC_N]

Narrow Body (R-14)

Dimensions shown in millimeters and (inches)

ORDERING GUIDE

Model1 Temperature Range Package Description Package Option Branding

AD8276ARMZ −40°C to +85°C 8-Lead MSOP RM-8 H1P
AD8276ARMZ-R7 −40°C to +85°C 8-Lead MSOP, 7" Tape and Reel RM-8 H1P
AD8276ARMZ-RL −40°C to +85°C 8-Lead MSOP, 13" Tape and Reel RM-8 H1P
AD8276ARZ −40°C to +85°C 8-Lead SOIC_N R-8
AD8276ARZ-R7 −40°C to +85°C 8-Lead SOIC_N, 7" Tape and Reel R-8
AD8276ARZ-RL −40°C to +85°C 8-Lead SOIC_N, 13" Tape and Reel R-8
AD8276BRMZ −40°C to +85°C 8-Lead MSOP RM-8 H1Q
AD8276BRMZ-R7 −40°C to +85°C 8-Lead MSOP, 7" Tape and Reel RM-8 H1Q
AD8276BRMZ-RL −40°C to +85°C 8-Lead MSOP, 13" Tape and Reel RM-8 H1Q
AD8276BRZ −40°C to +85°C 8-Lead SOIC_N R-8
AD8276BRZ-R7 −40°C to +85°C 8-Lead SOIC_N, 7" Tape and Reel R-8
AD8276BRZ-RL −40°C to +85°C 8-Lead SOIC_N, 13" Tape and Reel R-8
AD8277ARZ −40°C to +85°C 14-Lead SOIC_N R-14
AD8277ARZ-R7 −40°C to +85°C 14-Lead SOIC_N, 7" Tape and Reel R-14
AD8277ARZ-RL −40°C to +85°C 14-Lead SOIC_N, 13" Tape and Reel R-14
AD8277BRZ −40°C to +85°C 14-Lead SOIC_N R-14
AD8277BRZ-R7 −40°C to +85°C 14-Lead SOIC_N, 7" Tape and Reel R-14
AD8277BRZ-RL −40°C to +85°C 14-Lead SOIC_N, 13" Tape and Reel R-14

1

Z = RoHS Compliant Part.

©2009–2010 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D07692-0-4/10(B)

Rev. B | Page 20 of 20