Analog Devices AD8615, AD8616, AD8618 Service Manual

Precision, 20 MHz, CMOS, Rail-to-Rail

FEATURES

Low offset voltage: 65 μV max
Single-supply operation: 2.7 V to 5.5 V
Low noise: 8 nV/√Hz
Wide bandwidth: >20 MHz
Slew rate: 12 V/μs
High output current: 150 mA
No phase reversal
Low input bias current: 1 pA
Low supply current: 2 mA
Unity-gain stable

APPLICATIONS

Barcode scanners
Battery-powered instrumentation
Multipole filters
Sensors
ASIC input or output amplifier
Audio
Photodiode amplification

GENERAL DESCRIPTION

The AD8615/AD8616/AD8618 are dual/quad, rail-to-rail, input
and output, single-supply amplifiers featuring very low offset
voltage, wide signal bandwidth, and low input voltage and

Input/Output Operational Amplifiers

AD8615/AD8616/AD8618

current noise. The parts use a patented trimming technique
that achieves superior precision without laser trimming.
The AD8615/AD8616/AD8618 are fully specified to operate
from 2.7 V to 5 V single supplies.

The combination of 20 MHz bandwidth, low offset, low noise,
and very low input bias current make these amplifiers useful in
a wide variety of applications. Filters, integrators, photodiode
amplifiers, and high impedance sensors all benefit from the
combination of performance features. AC applications benefit
from the wide bandwidth and low distortion. The
AD8615/AD8616/AD8618 offer the highest output drive
capability of the DigiTrim
line drivers and other low impedance applications.

Applications for the parts include portable and low powered
instrumentation, audio amplification for portable devices,
portable phone headsets, bar code scanners, and multipole
filters. The ability to swing rail-to-rail at both the input and
output enables designers to buffer CMOS ADCs, DACs, ASICs,
and other wide output swing devices in single-supply systems.

The AD8615/AD8616/AD8618 are specified over the extended
industrial (–40°C to +125°C) temperature range. The AD8615
is available in 5-lead TSOT-23 packages. The AD8616 is availa­ble in 8-lead MSOP and narrow SOIC surface-mount packages;
the MSOP version is available in tape and reel only. The
AD8618 is available in 14-lead SOIC and TSSOP packages.

TM

family, which is excellent for audio

PIN CONFIGURATIONS

5

4

8
7
6
5

8
7
6
5

V+

–IN

V+
OUT B
–IN B
+IN B

V+
OUT B
–IN B
+IN B

04648-B-050

04648-0-001

04648-0-002

1

OUT

AD8615

V–

2

TOP VIEW

(Not to Scale)

+IN

3

Figure 1. 5-Lead TSOT-23 (UJ-5)

OUT A

1

AD8616

2

–IN A
+IN A

3

TOP VIEW

(Not to Scale)

V–

4

Figure 2. 8-Lead MSOP (RM-8)

OUT A

1

V–

AD8616

2
3

TOP VIEW

(Not to Scale)

4

–IN A
+IN A

Figure 3. 8-Lead SOIC (R-8)

Rev. C

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.

OUT A

–IN A
+IN A

+IN B
–IN B

OUT B

1

V+

AD8618

7

OUT D

14

–IN D
+IN D
V–
+IN C
–IN C

8

OUT C

04648-0-048

Figure 4. 14-Lead TSSOP (RU-14)

OUT A

–

IN A

+IN A

+IN B
–IN B

OUT B

1

2

3

AD8618

4

V+

5

6

7

14

13

12

11

10

9

8

OUT D
–IN D
+IN D
V–
+IN C
–IN C
OUT C

04648-0-049

Figure 5. 14-Lead SOIC (R-14)

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: [phone] www.analog.com
Fax: [phone] © 2005 Analog Devices, Inc. All rights reserved.

AD8615/AD8616/AD8618

TABLE OF CONTENTS

Specifications..................................................................................... 3

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

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

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

Typical Performance Characteristics............................................. 6

Applications..................................................................................... 11

Input Overvoltage Protection................................................... 11

Output Phase Reversal............................................................... 11

Driving Capacitive Loads.......................................................... 11

REVISION HISTORY

6/05—Rev. B to Rev. C

Change to Table 1 .........................................................................3

Change to Table 2 .........................................................................4

Change to Figure 20 ..................................................................... 8

1/05—Rev. A to Rev. B

Added AD8615 ...............................................................Universal

Changes to Figure 12.................................................................... 8

Deleted Figure 19; Renumbered Subsequent Figures.............. 8

Changes to Figure 20.................................................................... 9

Changes to Figure 29.................................................................. 10

Changes to Figure 31.................................................................. 11

Deleted Figure 34; Renumbered Subsequent Figures............ 11

Deleted Figure 35; Renumbered Subsequent Figures............ 35

Overload Recovery Time .......................................................... 12

D/A Conversion ......................................................................... 12

Low Noise Applications............................................................. 12

High Speed Photodiode Preamplifier...................................... 13

Active Filters ............................................................................... 13

Power Dissipation....................................................................... 13

Power Calculations for Varying or Unknown Loads............. 14

Outline Dimensions .......................................................................15

Ordering Guide .......................................................................... 17

4/04—Rev. 0 to Rev. A

Added AD8618 ...............................................................Universal

Updated Outline Dimensions................................................... 16

1/04—Revision 0: Initial Version

Rev. C | Page 2 of 20

AD8615/AD8616/AD8618

SPECIFICATIONS

VS =5 V, VCM = VS/2, TA = 25°C, unless otherwise noted.

Table 1.

Parameter Symbol Conditions Min Typ Max Unit

INPUT CHARACTERISTICS

Offset Voltage AD8616/AD8618/

V

OS

AD8615

V

−40°C < TA < +125°C 800 μV
/∆T −40°C < TA < +125°C

Offset Voltage Drift AD8616/AD8618/

∆V

OS

AD8615

Input Bias Current I

B

−40°C < TA < +85°C 50 pA

−40°C < TA < +125°C 550 pA

Input Offset Current I

OS

−40°C < TA < +85°C 50 pA

−40°C < TA < +125°C 250 pA

Input Voltage Range 0 5 V
Common-Mode Rejection Ratio CMRR VCM = 0 V to 4.5 V 80 100 dB
Large Signal Voltage Gain A
Input Capacitance C

C

VO

DIFF

CM

OUTPUT CHARACTERISTICS

Output Voltage High V

OH

I

−40°C < TA < +125°C 4.7 V
Output Voltage Low V

OL

I

−40°C < TA < +125°C 200 mV

Output Current I
Closed-Loop Output Impedance Z

OUT

OUT

POWER SUPPLY

Power Supply Rejection Ratio PSRR VS = 2.7 V to 5.5 V 70 90 dB
Supply Current per Amplifier I

SY

−40°C < TA < +125°C 2.5 mA

DYNAMIC PERFORMANCE

Slew Rate SR RL = 2 kΩ 12 V/μs
Settling Time t

s

Gain Bandwidth Product GBP 24 MHz
Phase Margin Ø

m

NOISE PERFORMANCE

Peak-to-Peak Noise en p-p 0.1 Hz to 10 Hz 2.4 μV
Voltage Noise Density e

n

f = 10 kHz 7 nV/√Hz

Current Noise Density i

n

Channel Separation Cs f = 10 kHz –115 dB

f = 100 kHz –110 dB

VS = 3.5 V at VCM = 0.5 V and 3.0 V

= 0 V to 5 V 80 500 μV

CM

23
23

1.5
3

60
100

7
10

μV
μV

μV/°C
μV/°C

0.2 1 pA

0.1 0.5 pA

RL = 2 kΩ, VO = 0.5 V to 5 V 105 1500 V/mV

2.5 pF

6.7 pF

IL = 1 mA 4.98 4.99 V

= 10 mA 4.88 4.92 V

L

IL = 1 mA 7.5 15 mV

= 10 mA 70 100 mV

L

±150 mA
f = 1 MHz, AV = 1 3 Ω

VO = 0 V 1.7 2.0 mA

To 0.01% <0.5 μs

63 Degrees

f = 1 kHz 10 nV/√Hz

f = 1 kHz 0.05 pA/√Hz

Rev. C | Page 3 of 20

AD8615/AD8616/AD8618

VS = 2.7 V, VCM = VS/2, TA = 25°C, unless otherwise noted.

Table 2.

Parameter Symbol Conditions Min Typ Max Unit

INPUT CHARACTERISTICS

Offset Voltage AD8616/AD8618/

V

OS

AD8615

V

−40°C < TA < +125°C 800 μV
/∆T −40°C < TA < +125°C

Offset Voltage Drift AD8616/AD8618/

∆V

OS

AD8615

Input Bias Current I

B

−40°C < TA < +85°C 50 pA

−40°C < TA < +125°C 550 pA

Input Offset Current I

OS

−40°C < TA < +85°C 50 pA

−40°C < TA < +125°C 250 pA

Input Voltage Range 0 2.7 V
Common-Mode Rejection Ratio CMRR VCM = 0 V to 2.7 V 80 100 dB
Large Signal Voltage Gain A
Input Capacitance C

C

VO

DIFF

CM

OUTPUT CHARACTERISTICS

Output Voltage High V

OH

−40°C < TA < +125°C 2.6 V

Output Voltage Low V

OL

−40°C < TA < +125°C 30 mV

Output Current I
Closed-Loop Output Impedance Z

OUT

OUT

POWER SUPPLY

Power Supply Rejection Ratio PSRR VS = 2.7 V to 5.5 V 70 90 dB
Supply Current per Amplifier I

SY

−40°C < TA < +125°C 2.5 mA

DYNAMIC PERFORMANCE

Slew Rate SR RL = 2 kΩ 12 V/μs
Settling Time t

s

Gain Bandwidth Product GBP 23 MHz
Phase Margin Ø

m

NOISE PERFORMANCE

Peak-to-Peak Noise en p-p 0.1 Hz to 10 Hz 2.1 μV
Voltage Noise Density e

n

f = 10 kHz 7 nV/√Hz
Current Noise Density i

n

Channel Separation Cs f = 10 kHz –115 dB

f = 100 kHz –110 dB

VS = 3.5 V at VCM = 0.5 V and 3.0 V

= 0 V to 2.7 V 80 500 μV

CM

23
23

1.5
3

65
100

7
10

μV
μV

μV/°C
μV/°C

0.2 1 pA

0.1 0.5 pA

RL = 2 kΩ, VO = 0.5 V to 2.2 V 55 150 V/mV

2.5 pF

7.8 pF

IL = 1 mA 2.65 2.68 V

IL = 1 mA 11 25 mV

±50 mA
f = 1 MHz, AV = 1 3 Ω

VO = 0 V 1.7 2 mA

To 0.01% < 0.3 μs

42 Degrees

f = 1 kHz 10 nV/√Hz

f = 1 kHz 0.05 pA/√Hz

Rev. C | Page 4 of 20

AD8615/AD8616/AD8618

ABSOLUTE MAXIMUM RATINGS

Table 3.

Parameter Rating

Supply Voltage 6 V
Input Voltage GND to V
Differential Input Voltage ±3 V
Output Short-Circuit Duration to GND Indefinite
Storage Temperature –65°C to +150°C
Operating Temperature Range –40°C to +125°C
Lead Temperature Range (Soldering 60 sec) 300°C
Junction Temperature 150°C

S

Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only and 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.

ESD CAUTION

ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on
the human body and test equipment and can discharge without detection. Although this product features
proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy
electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance
degradation or loss of functionality.

THERMAL RESISTANCE

θJA is specified for the worst-case conditions, that is, θJA is
specified for device soldered in circuit board for surface-mount
packages.

Table 4.

Package Type θ

5–Lead TSOT-23 (UJ) 207 61 °C/W
8-Lead MSOP (RM) 210 45 °C/W
8-Lead SOIC (R) 158 43 °C/W
14-Lead SOIC (R) 120 36 °C/W
14-Lead TSSOP (RU) 180 35 °C/W

JA

θ

Unit

JC

Rev. C | Page 5 of 20

AD8615/AD8616/AD8618

TYPICAL PERFORMANCE CHARACTERISTICS

2200

VS = 5V

2000

T

=25°C

A

V

= 0V TO 5V

CM

1800
1600
1400
1200
1000

800
600

NUMBER OF AMPLIFIERS

400
200

0

–700 –500 –300 –100 100 300 500 700

μ

OFFSET VOLTAGE (

Figure 6. Input Offset Voltage Distribution

V)

04648-0-003

350

VS = ±2.5V

300

250

200

150

100

INPUT BIAS CURRENT (pA)

50

0

0 25 50 75 100 125

TEMPERATURE (°C)

Figure 9. Input Bias Current vs. Temperature

04648-0-006

22

OS

(μV/°C)

VS = ±2.5V
T

=–40°CTO+125°C

A

V

= 0V

CM

NUMBER OF AMPLIFIERS

20
18
16
14
12
10

8
6
4
2
0

024681012

TCV

Figure 7. Offset Voltage Drift Distribution

500

VS = 5V

400

T

=25°C

A

300

V)

μ

200

100

0

–100

–200

INPUT OFFSET VOLTAGE (

–300

–400

–500

0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

COMMON-MODE VOLTAGE (V)

Figure 8. Input Offset Voltage vs. Common-Mode Voltage

(200 Units, Five Wafer Lots Including Process Skews)

04648-0-004

04648-0-005

1000

VS = 5V

= 25°C

T

A

100

(mV)

10

OUT

–V

SY

V

1

0.1

0.001 0.01 0.1 1 10

SOURCE

I

LOAD

SINK

(mA)

Figure 10. Output Voltage to Supply Rail vs. Load Current

120

VS = 5V

100

80

60

40

OUTPUT VOLTAGE (mV)

20

1mA LOAD

0

–40 –25 –10 5 20 35 50 65 80 95 110 125

10mA LOAD

TEMPERATURE (

°

C)

Figure 11. Output Saturation Voltage vs. Temperature

100

04648-B-007

04648-0-008

Rev. C | Page 6 of 20

AD8615/AD8616/AD8618

100

VS = ±2.5V

80

T

= 25°C

A

Ø

= 63°

m

60

40

20

0

GAIN (dB)

–20

–40

–60

–80

–100

1M 10M

FREQUENCY (Hz)

Figure 12. Open-Loop Gain and Phase vs. Frequency

60M

225

180

135

90

45
0

–45

–90

–135

–180
–225

PHASE (Degrees)

04648-B-009

120

100

80

60

CMRR (dB)

40

20

0

10k1k 100k 1M 10M

FREQUENCY (Hz)

Figure 15. Common-Mode Rejection Ratio vs. Frequency

VS = ±2.5V

04648-0-012

5.0

VS = 5.0V

4.5
V

= 4.9V p-p

IN

T

= 25°C

4.0

A

R

= 2k

Ω

L

AV = 1

3.5

3.0

2.5

2.0

1.5

OUTPUT SWING (V p-p)

1.0

0.5

0

10k1k 100k 1M 10M

FREQUENCY (Hz)

Figure 13. Closed-Loop Output Voltage Swing

100

VS = ±2.5V

90

80

70

60

50

40

30

OUTPUT IMPEDANCE (Ω)

20

10

0

1k 10k 100k 1M 10M 100M

AV = 100 AV = 1

AV = 10

FREQUENCY (Hz)

Figure 14. Output Impedance vs. Frequency

04648-0-010

04648-0-011

120

100

80

60

PSRR (dB)

40

20

0

10k1k 100k 1M 10M

FREQUENCY (Hz)

Figure 16. PSRR v s. Frequency

50

VS = 5V

45

=

∞

R

L

TA=25°C

40

= 1

A

V

35

30

25

20

15

10

SMALL-SIGNAL OVERSHOOT (%)

5

0

10 100 1000

CAPACITANCE (pF)

–OS

+OS

Figure 17. Small-Signal Overshoot vs. Load Capacitance

VS = ±2.5V

04648-0-013

04648-0-014

Rev. C | Page 7 of 20

AD8615/AD8616/AD8618

2.4

2.2

2.0

1.8

1.6

1.4

1.2

1.0

0.8

0.6

0.4

SUPPLY CURRENT PER AMPLIFIER (mA)

0.2
0

–40 –25 –10 5 20 35 50 65 80 95 110 125

VS = 2.7V

VS = 5V

TEMPERATURE (

°

C)

Figure 18. Supply Current vs. Temperature

04648-0-015

VS = 5V
R

= 10k

Ω

L

CL = 200pF
A

= 1

V

VOLTAGE (50mV/DIV)

TIME (1μs/DIV)

04648-0-019

Figure 21. Small-Signal Transient Response

2000

1800

1600

1400

1200

1000

800

600

400

SUPPLY CURRENT PER AMPLIFIER (μA)

200

0

0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

SUPPLY VOLTAGE (V)

Figure 19. Supply Current vs. Supply Voltage

1k

)

0.5

100

VS = ±2.5V

= ±1.35V

V

S

04648-0-016

E (500mV/DIV)

VOLTAG

0.01

0.1

VS = 5V

= 10kΩ

R

L

= 200pF

C

L

= 1

A

V

TIME (1μs/DIV)

Figure 22. Large-Signal Transient Response

VS = ±2.5V
V

= 0.5V rms

IN

A

= 1

V

BW = 22kHz
R

= 100k

Ω

L

04648-0-020

10

VOLTAGE NOISE DENSITY (nV/ Hz

1

10 100 1k 10k 100k

FREQUENCY (Hz)

Figure 20. Voltage Noise Density vs. Frequency

04648-B-017

Rev. C | Page 8 of 20

THD+N (%)

0.001

0.0001
20 100 1k 20k

FREQUENCY (Hz)

Figure 23. THD + N

04648-0-021

AD8615/AD8616/AD8618

500

VS = ±2.5V

= 2V p-p

V

IN

= 10

A

V

VOLTAGE (2V/DIV)

TIME (200ns/DIV)

04648-0-022

Figure 24. Settling Time

VS = 2.7V

VOLTAGE (1μV/DIV)

TIME (1s/DIV)

04648-0-023

Figure 25. 0.1 Hz to 10 Hz Input Voltage Noise

VS = 2.7V

400

T

=25°C

A

300

200

100

0

–100

–200

INPUT OFFSET VOLTAGE (μV)

–300

–400

–500

0 0.3 0.6 0.9 1.2 1.5 1.8 2.1 2.4 2.7

COMMON-MODE VOLTAGE (V)

Figure 27. Input Offset Voltage vs. Common-Mode Voltage

(200 Units, Five Wafer Lots Including Process Skews)

500

VS = 3.5V

400

T

= 25°C

A

300

V)

μ

200

100

0

–100

–200

INPUT OFFSET VOLTAGE (

–300

–400

–500

0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

COMMON-MODE VOLTAGE (V)

Figure 28. Input Offset Voltage vs. Common-Mode Voltage

(200 Units, Five Wafer Lots Including Process Skews)

04648-0-025

04648-0-026

1400

VS = 2.7V
T

= 25°

C

A

1200

V

= 0V TO 2.7V

CM

1000

800

600

400

NUMBER OF AMPLIFIERS

200

0

–700 –500 –300 –100 100 300 500 700

OFFSET VOLTAGE (μV)

Figure 26. Input Offset Voltage Distribution

04648-0-024

Rev. C | Page 9 of 20

1000

VS = ±1.35V
T

= 25°C

A

100

(mV)

10

OUT

-V

SY

V

1

0.1

0.001 0.01 0.1 1 10

SOURCE

I

(mA)

LOAD

SINK

Figure 29. Output Voltage to Supply Rail vs. Load Current

04648-B-027

AD8615/AD8616/AD8618

18

VS = 2.7V

16

14

12

10

8

6

OUTPUT VOLTAGE (mV)

4

2

0

VOL@ 1mA LOAD

–40 –25 –10 5 20 35 50 65 80 95 110 125

Figure 30. Output Saturation Voltage vs. Temperature

VOH@ 1mA LOAD

TEMPERATURE (°C)

04648-0-028

50

VS = ±1.35V

45

=

∞

R

L

TA=25°C

40

= 1

A

V

35

30

25

20

15

10

SMALL SIGNAL OVERSHOOT (%)

5

0

10 100 1000

CAPACITANCE (pF)

–OS

+OS

Figure 33. Small-Signal Overshoot vs. Load Capacitance

04648-0-0331

100

VS = ±1.35V

80

= 25°C

T

A

= 42°

Ø

m

60

40

20

0

GAIN (dB)

–20

–40

–60

–80

–100

1M 10M

FREQUENCY (Hz)

Figure 31. Open-Loop Gain and Phase vs. Frequency

2.7

VS = 2.7V

2.4

2.1

1.8

1.5

1.2

0.9

OUTPUT SWING (V p-p)

0.6

0.3

= 2.6V p-p

V

IN

= 25°C

T

A

= 2k

Ω

R

L

AV = 1

0

10k1k 100k 1M 10M

FREQUENCY (Hz)

Figure 32. Closed-Loop Output Voltage Swing vs. Frequency

60M

225

180

135

90

45
0

–45

–90

–135

–180
–225

PHASE (Degrees)

04648-B-029

04648-0-030

VS = 2.7V

= 10kΩ

R

L

= 200pF

C

L

A

= 1

V

VOLTAGE (50mV/DIV)

TIME (1μs/DIV)

04648-0-034

Figure 34. Small-Signal Transient Response

VS = 2.7V

= 10kΩ

R

L

= 200pF

C

L

= 1

A

V

VOLTAGE (500mV/DIV)

TIME (1μs/DIV)

04648-0-035

Figure 35. Large-Signal Transient Response

Rev. C | Page 10 of 20

AD8615/AD8616/AD8618

APPLICATIONS

INPUT OVERVOLTAGE PROTECTION

The AD8615/AD8616/AD8618 have internal protective cir­cuitry that allows voltages exceeding the supply to be applied
at the input.

It is recommended, however, not to apply voltages that exceed
the supplies by more than 1.5 V at either input of the amplifier.
If a higher input voltage is applied, series resistors should be
used to limit the current flowing into the inputs.

The input current should be limited to <5 mA. The extremely
low input bias current allows the use of larger resistors, which
allows the user to apply higher voltages at the inputs. The use
of these resistors adds thermal noise, which contributes to the
overall output voltage noise of the amplifier.

For example, a 10 kΩ resistor has less than 13 nV/√Hz of
thermal noise and less than 10 nV of error voltage at room
temperature.

This reduces the overshoot and minimizes ringing, which
in turn improves the frequency response of the AD8615/
AD8616/AD8618. One simple technique for compensation is
the snubber, which consists of a simple RC network. With this
circuit in place, output swing is maintained and the amplifier
is stable at all gains.

Figure 38 shows the implementation of the snubber, which
reduces overshoot by more than 30% and eliminates ringing
that can cause instability. Using the snubber does not recover
the loss of bandwidth incurred from a heavy capacitive load.

VS = ±2.5V

= 1

A

V

= 500pF

C

L

OUTPUT PHASE REVERSAL

The AD8615/AD8616/AD8618 are immune to phase
inversion, a phenomenon that occurs when the voltage
applied at the input of the amplifier exceeds the maxi­mum input common mode.

Phase reversal can cause permanent damage to the ampli­fier and can create lock-ups in systems with feedback loops.

VS= ±2.5V
V

= 6V p-p

IN

A

= 1

V

R

= 10kΩ

L

V

OUT

VOLTAGE (2V/DIV)

TIME (2ms/DIV)

Figure 36. No Phase Reversal

V

IN

04648-0-036

VOLTAGE (100mV/DIV)

TIME (2μs/DIV)

Figure 37. Driving Heavy Capacitive Loads Without Compensation

V

CC

+

V–
V+

+
–

–

200mV

200Ω

500pF

V

EE

500pF

04648-0-038

Figure 38. Snubber Network

VS = ±2.5V

= 1

A

V

= 200

Ω

R

S

CS = 500pF

= 500pF

C

L

04648-0-037

DRIVING CAPACITIVE LOADS

Although the AD8615/AD8616/AD8618 are capable of driving
capacitive loads of up to 500 pF without oscillating, a large
amount of overshoot is present when operating at frequencies
above 100 kHz. This is especially true when the amplifier is
configured in positive unity gain (worst case). When such large
capacitive loads are required, the use of external compensation
is highly recommended.

Rev. C | Page 11 of 20

VOLTAGE (100mV/DIV)

TIME (10μs/DIV)

Figure 39. Driving Heavy Capacitive Loads Using the Snubber Network

04648-0-039

AD8615/AD8616/AD8618

0V0

OVERLOAD RECOVERY TIME

Overload recovery time is the time it takes the output of the
amplifier to come out of saturation and recover to its linear
region. Overload recovery is particularly important in applica­tions where small signals must be amplified in the presence of
large transients.

Figure 40 and Figure 41 show the positive and
negative overload recovery times of the AD8616. In both cases,
the time elapsed before the AD8616 comes out of saturation is
less than 1 μs. In addition, the symmetry between the positive
and negative recovery times allows excellent signal rectification
without distortion to the output signal.

VS = ±2.5V

= 10kΩ

R

L

= 100

A

V

V

IN

= 50mV

04648-0-040

04648-0-041

0V

0V

V

+2.5V

–50mV

VS = ±2.5V

= 10kΩ

R

L

A

= 100

V

= 50mV

V

IN

–2.5V

+50mV

TIME (1μs/DIV)

Figure 40. Positive Overload Recovery

TIME (1μs/DIV)

Figure 41. Negative Overload Recovery

D/A CONVERSION

The AD8616 can be used at the output of high resolution DACs.
Their low offset voltage, fast slew rate, and fast settling time
make the parts suitable to buffer voltage output or current
output DACs.

SERIAL

INTERFACE

0.1

μ

F

CS
DIN
SCLK

LDAC

5V 2.5V

DD

0.1

REFFV

AD5542

10

μ

F

+

μ

F

REFS

AGNDDGND

OUT

1/2
AD8616

UNIPOLAR

OUTPUT

Figure 42. Buffering DAC Output

LOW NOISE APPLICATIONS

Although the AD8618 typically has less than 8 nV/√Hz of
voltage noise density at 1 kHz, it is possible to reduce it fur­ther. A simple method is to connect the amplifiers in parallel,
as shown in
by the square root of the number of amplifiers. In this case, the
total noise is approximately 4 nV/√Hz at room temperature.
The 100 Ω resistor limits the current and provides an effective
output resistance of 50 Ω.

V

Figure 43. The total noise at the output is divided

IN

3

V+

R1

10Ω

R4

10Ω

R7

10Ω

R10
10Ω

2

3

2

3

2

3

2

V–

1kΩ

V+
V–

1kΩ

V+
V–

1kΩ

V+
V–

R11
1kΩ

1

R2

1

R5

1

R8

1

Figure 43. Noise Reduction

100Ω

100Ω

100Ω

R12

100Ω

R3

R6

V

OUT

R9

04648-0-043

04648-0-042

Figure 42 shows an example of the AD8616 at the output of the
AD5542. The AD8616’s rail-to-rail output and low distortion
help maintain the accuracy needed in data acquisition systems
and automated test equipment.

Rev. C | Page 12 of 20

AD8615/AD8616/AD8618

HIGH SPEED PHOTODIODE PREAMPLIFIER

The AD8615/AD8616/AD8618 are excellent choices for I-to-V
conversions. The very low input bias, low current noise, and
high unity-gain bandwidth of the parts make them suitable,
especially for high speed photodiode preamps.

In high speed photodiode applications, the diode is operated
in a photoconductive mode (reverse biased). This lowers the
junction capacitance at the expense of an increase in the
amount of dark current that flows out of the diode.

The total input capacitance, C1, is the sum of the diode and op
amp input capacitances. This creates a feedback pole that causes
degradation of the phase margin, making the op amp unstable.
Therefore, it is necessary to use a capacitor in the feedback to
compensate for this pole.

To get the maximum signal bandwidth, select

1C

f2R

U

C2

R2

+2.5V

–

C

R

SH

C

D

IN

V–
V+

+

where

2Cπ=

2

f

is the unity-gain bandwidth of the amplifier.

U

I

D

10

0

–10

GAIN (dB)

–20

–30

–40

10.1 10 100 1k 10k 100k 1M
FREQUENCY (Hz)

04648-0-046

Figure 46. Second-Order Butterworth, Low-Pass Filter Frequency Response

POWER DISSIPATION

Although the AD8615/AD8616/AD8618 are capable of
providing load currents up to 150 mA, the usable output, load
current, and drive capability is limited to the maximum power
dissipation allowed by the device package.

In any application, the absolute maximum junction temperature
for the AD8615/AD8616/AD8618 is 150°C. This should never
be exceeded because the device could suffer premature failure.
Accurately measuring power dissipation of an integrated circuit
is not always a straightforward exercise;
for setting a safe output current drive level or selecting a heat
sink for the package options available on the AD8616.

1.5

Figure 47 is a design aid

–V

BIAS

–2.5V

04648-0-044

Figure 44. High Speed Photodiode Preamplifier

ACTIVE FILTERS

The low input-bias current and high unity-gain bandwidth
of the AD8616 make it an excellent choice for precision filter
design.

Figure 45 shows the implementation of a second-order, low­pass filter. The Butterworth response has a corner frequency
of 100 kHz and a phase shift of 90°. The frequency response
is shown in

Figure 46.

2nF

V

CC

1.1k

1.1k

V

Ω

IN

Ω

1nF

Figure 45. Second-Order, Low-Pass Filter

V–
V+

V

EE

04648-0-045

1.0

0.5

POWER DISSIPATION (W)

0

20

0

SOIC

MSOP

40 60 80 120100 140

TEMPERATURE (°C)

Figure 47. Maximum Power Dissipation vs. Ambient Temperature

04648-0-047

Rev. C | Page 13 of 20

AD8615/AD8616/AD8618

These thermal resistance curves were determined using
the AD8616 thermal resistance data for each package and
a maximum junction temperature of 150°C. The following
formula can be used to calculate the internal junction tem­perature of the AD8615/AD8616/AD8618 for any application:

T

= P

× θJA + T

J

DISS

where:

T

= junction temperature

J

P

= power dissipation

DISS

θ

= package thermal resistance, junction-to-case

JA

T

= ambient temperature of the circuit

A

To calculate the power dissipated by the AD8615/
AD8616/AD8618, use

P

= I

DISS

LOAD

A

× (VS – V

OUT

)

Calculating Power by Measuring Ambient and Case Temperature

The two equations for calculating junction temperature are

T

= TA + P θ

J

JA

where:

T

= junction temperature

J

T

= ambient temperature

A

θ

= the junction-to-ambient thermal resistance

JA

T

= TC + P θ

where T

J

is case temperature and θ

C

JC

and θJC are given in the

JA

data sheet.

The two equations for calculating P (power) are

T

+ P θ

A

= TC + P θ

JA

JC

where:

I

= output load current

LOAD

V

= supply voltage

S

V

= output voltage

OUT

The quantity within the parentheses is the maximum voltage
developed across either output transistor.

POWER CALCULATIONS FOR VARYING OR UNKNOWN LOADS

Often, calculating power dissipated by an integrated circuit to
determine if the device is being operated in a safe range is not
as simple as it might seem. In many cases, power cannot be
directly measured. This may be the result of irregular output
waveforms or varying loads. Indirect methods of measuring
power are required.

There are two methods to calculate power dissipated by
an integrated circuit. The first is to measure the package
temperature and the board temperature. The second is
to directly measure the circuits supply current.

P = (TA – T

C

)/(θ

JC

– θ

)

JA

Once power has been determined, it is necessary to recalculate
the junction temperature to ensure that it has not been
exceeded.

The temperature should be measured directly on and near the
package, but not touching it. Measuring the package can be
difficult. A very small bimetallic junction glued to the package
can be used, or an infrared sensing device can be used if the
spot size is small enough.

Calculating Power by Measuring Supply Current

Power can be calculated directly if the supply voltage and
current are known. However, the supply current can have a dc
component with a pulse directed into a capacitive load, which
could make the rms current very difficult to calculate. This
difficulty can be overcome by lifting the supply pin and
inserting an rms current meter into the circuit. For this method
to work, make sure the current is delivered by the supply pin
being measured. This is usually a good method in a single­supply system; however, if the system uses dual supplies, both
supplies may need to be monitored.

Rev. C | Page 14 of 20

AD8615/AD8616/AD8618

OUTLINE DIMENSIONS

3.00
BSC

8

5

3.00
BSC

1

PIN 1

0.65 BSC

0.15

0.00

0.38

0.22

COPLANARITY

0.10
COMPLIANT TO JEDEC STANDARDS MO-187-AA

BSC

4

SEATING
PLANE

4.90

1.10 MAX

0.23

0.08

8°
0°

0.80

0.60

0.40

Figure 48. 8-Lead Mini Small Outline Package [MSOP]

(RM-8)

Dimensions shown in millimeters

5.00 (0.1968)

4.80 (0.1890)

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 ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN

85

1.27 (0.0500)

SEATING

PLANE

COMPLIANT TO JEDEC STANDARDS MS-012-AA

BSC

6.20 (0.2440)

5.80 (0.2284)

41

1.75 (0.0688)

1.35 (0.0532)

0.51 (0.0201)

0.31 (0.0122)

0.25 (0.0098)

0.17 (0.0067)

0.50 (0.0196)

0.25 (0.0099)

8°

1.27 (0.0500)

0°

0.40 (0.0157)

Figure 49. 8-Lead Standard Small Outline Package [SOIC]

Narrow Body (R-8)

Dimensions shown in millimeters and (inches)

× 45°

8.75 (0.3445)

8.55 (0.3366)

4.00 (0.1575)

3.80 (0.1496)

0.25 (0.0098)

0.10 (0.0039)

COPLANARITY

0.10

CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS
(IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR
REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN

14
1

1.27 (0.0500)
BSC

0.51 (0.0201)

0.31 (0.0122)

COMPLIANT TO JEDEC STANDARDS MS-012-AB

8

6.20 (0.2441)

7

5.80 (0.2283)

SEATING
PLANE

1.75 (0.0689)

1.35 (0.0531)

0.25 (0.0098)

0.17 (0.0067)

0.50 (0.0197)

0.25 (0.0098)

8°
0°

1.27 (0.0500)

0.40 (0.0157)

× 45°

Figure 50. 14-Lead Standard Small Outline Package [SOIC]

Narrow Body (R-14)

Dimensions shown in millimeters and (inches)

5.10

5.00

4.90

14

4.50

4.40

4.30

PIN 1

1.05

1.00

0.80

0.65

BSC

0.15

0.05

COMPLIANT TO JEDEC STANDARDS MO-153-AB-1

0.30

0.19

8

6.40
BSC

71

SEATING
PLANE

1.20
MAX

COPLANARITY

0.20

0.09

0.10

8°
0°

0.75

0.60

0.45

Figure 51. 14-Lead Thin Shrink Small Outline Package [TSSOP]

(RU-14)

Dimensions shown in millimeters

Rev. C | Page 15 of 20

AD8615/AD8616/AD8618

2.90 BSC

54

0.50

0.30

2.80 BSC

0.95 BSC

*

1.00 MAX

SEATING
PLANE

0.20

0.08

1.60 BSC

*

0.90

0.87

0.84

0.10 MAX

123

PIN 1

1.90
BSC

*

COMPLIANT TO JEDEC STANDARDS MO-193-AB WITH

THE EXCEPTION OF PACKAGE HEIGHT AND THICKNESS.

Figure 52. 5-Lead Thin Small Outline Transistor Package [TSOT ]

(UJ-5)

Dimensions shown in millimeters

8°
4°
0°

0.60

0.45

0.30

Rev. C | Page 16 of 20

AD8615/AD8616/AD8618

ORDERING GUIDE

Model Temperature Range Package Description Package Option Branding

AD8615AUJZ-R2
AD8615AUJZ-REEL
AD8615AUJZ-REEL7
AD8616ARM-R2 –40°C to +125°C 8-Lead MSOP RM-8 BLA
AD8616ARM-REEL –40°C to +125°C 8-Lead MSOP RM-8 BLA
AD8616ARMZ-R2
AD8616ARMZ-REEL
AD8616AR –40°C to +125°C 8-Lead SOIC R-8
AD8616AR-REEL –40°C to +125°C 8-Lead SOIC R-8
AD8616AR-REEL7 –40°C to +125°C 8-Lead SOIC R-8
AD8616ARZ
AD8616ARZ-REEL
AD8616ARZ-REEL7
AD8618AR –40°C to +125°C 14-Lead SOIC R-14
AD8618AR-REEL –40°C to +125°C 14-Lead SOIC R-14
AD8618AR-REEL7 –40°C to +125°C 14-Lead SOIC R-14
AD8618ARZ
AD8618ARZ-REEL
AD8618ARZ-REEL7
AD8618ARU –40°C to +125°C 14-Lead TSSOP RU-14
AD8618ARU-REEL –40°C to +125°C 14-Lead TSSOP RU-14
AD8618ARUZ
AD8618ARUZ-REEL

1

Z = Pb-free part.

1

1

1

1

1

1

1

1

1

1

1

1

–40°C to +125°C 5-Lead TSOT-23 UJ-5 BKA
–40°C to +125°C 5-Lead TSOT-23 UJ-5 BKA

1

–40°C to +125°C 5-Lead TSOT-23 UJ-5 BKA

–40°C to +125°C 8-Lead MSOP RM-8
–40°C to +125°C 8-Lead MSOP RM-8

–40°C to +125°C 8-Lead SOIC R-8
–40°C to +125°C 8-Lead SOIC R-8
–40°C to +125°C 8-Lead SOIC R-8

–40°C to +125°C 14-Lead SOIC R-14
–40°C to +125°C 14-Lead SOIC R-14
–40°C to +125°C 14-Lead SOIC R-14

–40°C to +125°C 14-Lead TSSOP RU-14
–40°C to +125°C 14-Lead TSSOP RU-14

A0K
A0K

Rev. C | Page 17 of 20

AD8615/AD8616/AD8618

NOTES

Rev. C | Page 18 of 20

AD8615/AD8616/AD8618

NOTES

Rev. C | Page 19 of 20

AD8615/AD8616/AD8618

NOTES

© 2005 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.

D04648–0–6/05(C)

Rev. C | Page 20 of 20