ANALOG DEVICES AD844 Service Manual

60 MHz 2000 V/μs

FEATURES

Wide bandwidth

60 MHz at gain of −1

33 MHz at gain of −10
Slew rate: 2000 V/μs
20 MHz full power bandwidth, 20 V p-p, R
Fast settling: 100 ns to 0.1% (10 V step)
Differential gain error: 0.03% at 4.4 MHz
Differential phase error: 0.16° at 4.4 MHz
Low offset voltage: 150 μV maximum (B Grade)
Low quiescent current: 6.5 mA
Available in tape and reel in accordance with

EIA-481-A standard

APPLICATIONS

Flash ADC input amplifiers
High speed current DAC interfaces
Video buffers and cable drivers
Pulse amplifiers

= 500 Ω

L

Monolithic Op Amp

AD844

FUNCTIONAL BLOCK DIAGRAMS

1

NULL

–IN

+IN

–V

Figure 1. 8-Lead PDIP (N) and 8-Lead CERDIP (Q) Packages

OFFSETNULL

Figure 2. 16-Lead SOIC (R) Package

AD844

2

3

4

S

TOP VIEW

(Not to Scale)

NC

1

2

3

–IN

4

NC

5 12

+IN

NC

6 11

AD844

7 10

V–

TOP VIEW

8 9

NC

(Not to Scale)

NC = NO CO NNECT

8

NULL

7

+V

S

OUTPUT

6

TZ

5

16

NC

15

OFFSETNULL

14

V+

13

NC

OUTPUT

TZ

NC

NC

00897-001

00897-002

GENERAL DESCRIPTION

The AD844 is a high speed monolithic operational amplifier
fabricated using the Analog Devices, Inc., junction isolated
complementary bipolar (CB) process. It combines high band­width and very fast large signal response with excellent dc
performance. Although optimized for use in current-to-voltage
applications and as an inverting mode amplifier, it is also suitable
for use in many noninverting applications.

The AD844 can be used in place of traditional op amps, but its
current feedback architecture results in much better ac perfor­mance, high linearity, and an exceptionally clean pulse response.

This type of op amp provides a closed-loop bandwidth that is
determined primarily by the feedback resistor and is almost
independent of the closed-loop gain. The AD844 is free from
the slew rate limitations inherent in traditional op amps and
other current-feedback op amps. Peak output rate of change can
be over 2000 V/μs for a full 20 V output step. Settling time is
typically 100 ns to 0.1%, and essentially independent of gain.
The AD844 can drive 50 Ω loads to ±2.5 V with low distortion
and is short-circuit protected to 80 mA.

The AD844 is available in four performance grades and three
package options. In the 16-lead SOIC (RW) package, the AD844J
is specified for the commercial temperature range of 0°C to 70°C.

The AD844A and AD844B are specified for the industrial
temperature range of −40°C to +85°C and are available in the
CERDIP (Q) package. The AD844A is also available in an 8-lead
PDIP (N). The AD844S is specified over the military temperature
range of −55°C to +125°C. It is available in the 8-lead CERDIP
(Q) package. A and S grade chips and devices processed to
MIL-STD-883B, Rev. C are also available.

PRODUCT HIGHLIGHTS

1. The AD844 is a versatile, low cost component providing an

excellent combination of ac and dc performance.

2. It is essentially free from slew rate limitations. Rise and fall

times are essentially independent of output level.

3. The AD844 can be operated from ±4.5 V to ±18 V power

supplies and is capable of driving loads down to 50 Ω, as
well as driving very large capacitive loads using an external
network.

4. The offset voltage and input bias currents of the AD844 are

laser trimmed to minimize dc errors; V
μV/°C and bias current drift is typically 9 nA/°C.

5. The AD844 exhibits excellent differential gain and

differential phase characteristics, making it suitable for a
variety of video applications with bandwidths up to 60 MHz.

6. The AD844 combines low distortion, low noise, and low

drift with wide bandwidth, making it outstanding as an
input amplifier for flash analog-to-digital converters (ADCs).

drift is typically 1

OS

Rev. F

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] ©1989–2009 Analog Devices, Inc. All rights reserved.

AD844

TABLE OF CONTENTS

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

Response as an Inverting Amplifier ......................................... 12

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

Functional Block Diagrams ............................................................. 1

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

Product Highlights ........................................................................... 1

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

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

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

Metallization Photograph ............................................................ 5

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

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

Inverting Gain-of-1 AC Characteristics .................................... 8

Inverting Gain-of-10 AC Characteristics .................................. 9

Inverting Gain-of-10 Pulse Response ...................................... 10

Noninverting Gain-of-10 AC Characteristics ........................ 11

Understanding the AD844 ............................................................ 12

Response as an I-V Converter .................................................. 13

Circuit Description of the AD844 ............................................ 13

Response as a Noninverting Amplifier .................................... 14

Noninverting Gain of 100 ......................................................... 14

Using the AD844 ............................................................................ 15

Board Layout ............................................................................... 15

Input Impedance ........................................................................ 15

Driving Large Capacitive Loads ............................................... 15

Settling Time ............................................................................... 15

DC Error Calculation ................................................................ 16

Noise ............................................................................................ 16

Video Cable Driver Using ±5 V Supplies ................................ 16

High Speed DAC Buffer ............................................................ 17

20 MHz Variable Gain Amplifier ............................................. 17

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

Open-Loop Behavior ................................................................. 12

REVISION HISTORY

2/09—Rev. E to Rev F

Updated Format .................................................................. Universal

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

Changes to Differential Phase Error Parameter, Table 1 ............. 3

Changes to Figure 13 ........................................................................ 8

Changes to Figure 18 ........................................................................ 9

Changes to Figure 23 and Figure 24 ............................................. 11

Changes to Figure 42 and High Speed DAC Buffer Section ..... 17

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

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

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

1/03 Data Sheet changed from REV. D to REV. E.

Updated Features ............................................................................... 1

Edit to TPC 18 ................................................................................... 7

Edits to Figure 13 and Figure 14 ................................................... 13

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

11/01 Data Sheet changed from REV. C to REV. D.

Edits to Specifications ...................................................................... 2

Edits to Absolute Maximum Ratings .............................................. 3

Edits to Ordering Guide ................................................................... 3

Rev. F | Page 2 of 20

AD844

SPECIFICATIONS

TA = 25°C and VS = ±15 V dc, unless otherwise noted.

Table 1.

AD844J/AD844A AD844B AD844S
Parameter Conditions Min Typ Max Min Typ Max Min Typ Max Unit

INPUT OFFSET VOLTAGE1

T

to T

MIN

75 500

MAX

vs. Temperature

vs. Supply 5 V to 18 V

Initial
T

to T

MIN

MAX

vs. Common Mode VCM = ±10 V

Initial
T

to T

MIN

MAX

INPUT BIAS CURRENT

Negative Input Bias Current1

T

to T

MIN

800 1500

MAX

vs. Temperature

vs. Supply 5 V to 18 V

Initial
T

to T

MIN

MAX

vs. Common Mode VCM = ±10 V

Initial
T

to T

MIN

MAX

Positive Input Bias Current1

T

to T

MIN

350 700

MAX

vs. Temperature

vs. Supply 5 V to 18 V

Initial
T

to T

MIN

MAX

vs. Common Mode VCM = ±10 V

Initial
T

to T

MIN

MAX

INPUT CHARACTERISTICS

Input Resistance

Negative Input
Positive Input 7 10

Input Capacitance

Negative Input
Positive Input

Input Common-Mode Voltage

±10 ±10 ±10 V

Range
INPUT VOLTAGE NOISE f ≥ 1 kHz 2
INPUT CURRENT NOISE

Negative Input f ≥ 1 kHz 10

Positive Input f ≥ 1 kHz 12
OPEN-LOOP TRANSRESISTANCE V
R

T

to T

MIN

1.3 2.0

MAX

= ±10 V

OUT

= 500 Ω 2.2 3.0

L

Transcapacitance 4.5
DIFFERENTIAL GAIN ERROR2 f = 4.4 MHz 0.03
DIFFERENTIAL PHASE ERROR2 f = 4.4 MHz 0.16

50 300

50 150
75 200

1 1 5

4 20

4 10

4 4 10

10 35

10 20

10 10 20

200 450

150 250
750 1100

9 9 15

175 250

175 200

220 220 240

90 160
110
150 400

90 110
110 150
100 200
300 500

3 3 7

80 150

80 100

100 100 120

90 150

90 120

130 130 190

50 65

2
2

Rev. F | Page 3 of 20

7 10 7 10

2
2 2 pF

10
12

2.8 3.0 2.2 3.0 MΩ

1.6 2.0

50 65

2 2 nV/√Hz

4.5

0.03

0.16 0.16 Degree

50 300 V
125 500 V
1 5 V/°C

4 20 V/V
4 20 V/V

10 35 V/V
10 35 V/V

200 450 nA
1900 2500 nA
20 30 nA/°C

175 250 nA/V
220 300 nA/V

90 160 nA/V
120 200 nA/V
100 400 nA
800 1300 nA
7 15 nA/°C

80 150 nA/V
120 200 nA/V

90 150 nA/V
140 200 nA/V

50 65 Ω

MΩ

2 pF

10 pV/√Hz
12 pV/√Hz

1.3 1.6 MΩ

4.5 pF

0.03 %

AD844

AD844J/AD844A AD844B AD844S
Parameter Conditions Min Typ Max Min Typ Max Min Typ Max Unit

FREQUENCY RESPONSE

Small Signal Bandwidth

Gain = −1 60
Gain = −10 33

TOTAL HARMONIC DISTORTION

SETTLING TIME

10 V Output Step ±15 V supplies

Gain = −1, to 0.1%5 100
Gain = −10, to 0.1%6 100

2 V Output Step ±5 V supplies

Gain = −1, to 0.1%
Gain = −10, to 0.1%6 100

OUTPUT SLEW RATE

FULL POWER BANDWIDTH THD = 3%

V

= 20 V p-p

OUT

V

= 2 V p-p

OUT

5

V

5

V

OUTPUT CHARACTERISTICS

Voltage RL = 500 Ω ±10 ±11
Short-Circuit Current 80
T

to T

MIN

60

MAX

Output Resistance Open loop 15

POWER SUPPLY

Operating Range ±4.5 ±18 ±4.5 ±18 ±4.5 ±18 V
Quiescent Current 6.5 7.5
T

to T

MIN

1

Rated performance after a 5 minute warm-up at TA = 25°C.

2

Input signal 285 mV p-p carrier (40 IRE) riding on 0 mV to 642 mV (90 IRE) ramp. RL = 100 Ω; R1, R2 = 300 Ω.

3

For gain = −1, input signal = 0 dBm, CL = 10 pF, RL = 500 Ω, R1 = 500 Ω, and R2 = 500 Ω in . Figure 29

4

For gain = −10, input signal = 0 dBm, CL =10 pF, RL = 500 Ω, R1 = 500 Ω, and R2 = 50 Ω in .

5

CL = 10 pF, RL = 500 Ω, R1 = 1 kΩ, R2 = 1 kΩ in .

6

CL = 10 pF, RL = 500 Ω, R1 = 500 Ω, R2 = 50 Ω in

7.5 8.5

MAX

3, 4

f = 100 kHz,

5

2 V rms

0.005

5

110

Overdriven

1200 2000

110
100
1200 2000

60
33

0.005

100
100

0.005 %

100 ns
100 ns

110 ns
100 ns
1200 2000 V/µs

60 MHz
33 MHz

input

= ±15 V 20

S

= ±5 V 20

S

Figure 29

Figure 29.

20 20 MHz

±10 ±11

Figure 29

20 20 MHz

80
60
15

6.5 7.5

7.5 8.5

±10 ±11
80 mA
60 mA
15 Ω

6.5 7.5 mA

7.5 8.5 mA

V

Rev. F | Page 4 of 20

AD844

–

V

ABSOLUTE MAXIMUM RATINGS

Table 2.

Parameter Ratings

Supply Voltage
Power Dissipation

1

1.1 W

±18 V

Output Short-Circuit Duration Indefinite
Input Common-Mode Voltage

±V

S

Differential Input Voltage 6 V
Inverting Input Current

Continuous 5 mA

Transient 10 mA
Storage Temperature Range (Q)

Storage Temperature Range (N, RW)
Lead Temperature (Soldering, 60 sec)

−65°C to +150°C

−65°C to +125°C
300°C

ESD Rating 1000 V

1

28-lead PDIP package: θJA = 90°C/W.

8-lead CERDIP package: θJA = 110°C/W.
16-lead SOIC package: θJA = 100°C/W.

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.

METALLIZATION PHOTOGRAPH

Contact factory for latest dimensions.

Dimensions shown in inches and (millimeters).

IN NULL NULL +

0.076
(1.9)

+IN –V

SUBSTRAT E CONNECTED T O +V

Figure 3. Die Photograph

S

0.095
(2.4)

TZ OUTPUT

ESD CAUTION

S

S

00897-003

Rev. F | Page 5 of 20

AD844

TYPICAL PERFORMANCE CHARACTERISTICS

TA = 25°C and VS = ±15 V, unless otherwise noted.

70

20

= 25°C

T

A

60

50

–3dB BANDWIDTH ( MHz)

40

30

SUPPLY VOLTAGE (±V)

Figure 4. −3 dB Bandwidth vs. Supply Voltage, R1 = R2 = 500 Ω

–60

1V rms

–70

–80

–90

–100

–110

SECOND HARMONIC

HARMONIC DISTORTION (dB)

–120

–130

100 1k 10k 100k

INPUT FREQUENCY (Hz)

THIRD HARMONIC

Figure 5. Harmonic Distortion vs. Input Frequency, R1 = R2 = 1 kΩ

5

RL =

∞

4

RL = 500Ω

3

2

R

= 50Ω

TRANSRESISTANCE (MΩ)

1

L

15

10

INPUT VOLTAGE (V)

5

200 5 10 15

00897-004

0

SUPPLY VOLTAGE (±V)

200 5 10 15

00897-007

Figure 7. Noninverting Input Voltage Swing vs. Supply Voltage

20

= 500Ω

R

L

T

= 25°C

A

15

10

OUTPUT VOLTAGE (V)

5

0

00897-005

SUPPLY VOLTAGE (±V)

200 5 10 15

00897-008

Figure 8. Output Voltage Swing vs. Supply Voltage

10

9

8

7

6

SUPPLY CURRENT (mA)

5

VS = ±15V

VS = ±5V

0

–50 0 50 100 150

TEMPERATURE (° C)

Figure 6. Transresistance vs. Temperature

00897-006

Rev. F | Page 6 of 20

4

TEMPERATURE ( -°C)

140–60 –40 –20 0 20 40 60 80 10 0 120

Figure 9. Quiescent Supply Current vs. Temperature and Supply Voltage

00897-009