Analog Devices AD795 b Datasheet

–

Low Power, Low Noise

a

FEATURES
Low Power Replacement for Burr-Brown
OPA-111, OPA-121 Op Amps
Low Noise

2.5 ␮V p-p max, 0.1 Hz to 10 Hz
11 nV/÷Hz max at 10 kHz

0.6 fA/÷Hz at 1 kHz

High DC Accuracy

250 ␮V max Offset Voltage
3 ␮V/ⴗC max Drift
1 pA max Input Bias Current
Low Power: 1.5 mA max Supply Current

APPLICATIONS
Low Noise Photodiode Preamps
CT Scanners
Precision l-to-V Converters

PRODUCT DESCRIPTION

The AD795 is a low noise, precision, FET input operational
amplifier. It offers both the low voltage noise and low offset drift
of a bipolar input op amp and the very low bias current of a
FET-input device. The 10
insures that input bias current is essentially independent of
common-mode voltage and supply voltage variations.

The AD795 has both excellent dc performance and a guaran­teed and tested maximum input voltage noise. It features 1 pA
maximum input bias current and 250 mV maximum offset volt-
age, along with low supply current of 1.5 mA max.

1k

14

W common-mode impedance

Precision FET Op Amp

AD795

CONNECTION DIAGRAMS

8-Pin SOIC (RN) Package

1

NC

2

–IN

3

+IN

4

V

S

AD795

NC = NO CONNECT

Furthermore, the AD795 features a guaranteed low input noise
of 2.5 mV p-p (0.1 Hz to 10 Hz) and a 11 nV/÷Hz max noise
level at 10 kHz. The AD795 has a fully specified and tested
input offset voltage drift of only 3 mV/∞C max.

The AD795 is useful for many high input impedance, low noise
applications. The AD795J and AD795K are rated over the
commercial temperature range of 0∞C to +70∞C.

The AD795 is available in 8-pin SOIC.

50

8

NC

+V

7

6

OUTPUT

5

NC

S

SAMPLE SIZE = 570

100

10

VOLTAGE NOISE SPECTRAL DENSITY – nV/÷Hz

1

10 100 10k1k

FREQUENCY – Hz

AD795 Voltage Noise Spectral Density

40

30

20

PERCENTAGE OF UNITS

10

0

–5

INPUT OFFSET VOLTAGE DRIFT – mV/∞C

5–4

43210–1–2–3

Typical Distribution of Average Input Offset Voltage Drift

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. No license is granted by implication or otherwise
under any patent or patent rights of Analog Devices.

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: [phone] www.analog.com
Fax: [phone] © Analog Devices, Inc., 2002

AD795–SPECIFICATIONS

(@ +25ⴗC and ⴞ15 V dc unless otherwise noted)

AD795JR

Parameter Conditions Min Typ Max Units

INPUT OFFSET VOLTAGE

1

Initial Offset 100 500 mV

Offset T

MIN–TMAX

300 1000 mV

vs. Temperature 310mV/∞C
vs. Supply (PSRR) 86 110 dB
vs. Supply (PSRR) T

INPUT BIAS CURRENT

2

MIN–TMAX

84 100 dB

Either Input VCM = 0 V 1 2/3 pA
Either Input @ T

=V

MAX

Either Input V
Offset Current V
Offset Current @ T

=V

MAX

OPEN-LOOP GAIN V

= 0 V 23 pA

CM

= +10 V 1 pA

CM

= 0 V 0.1 1.0 pA

CM

= 0 V 2 pA

CM

= ± 10 V

O

≥ 10 kW 110 120 dB

R

LOAD

R

≥ 10 kW 100 108 dB

LOAD

INPUT VOLTAGE NOISE 0.1 Hz to 10 Hz 1.0 3.3 mV p-p

f = 10 Hz 20 50 nV/÷Hz
f = 100 Hz 12 40 nV/÷Hz
f = 1 kHz 11 17 nV/÷Hz
f = 10 kHz 9 11 nV/÷Hz

INPUT CURRENT NOISE f = 0.1 Hz to 10 Hz 13 fA p-p

f = 1 kHz 0.6 fA/÷Hz

FREQUENCY RESPONSE

Unity Gain, Small Signal G = –1 1.6 MHz
Full Power Response V

Slew Rate, Unity Gain V

SETTLING TIME

3

= 20 V p-p

O

R

= 2 kW 16 kHz

LOAD

= 20 V p-p

OUT

R

= 2 kW 1V/ms

LOAD

To 0.1% 10 V Step 10 ms
To 0.01% 10 V Step 11 ms
Overload Recovery

4

50% Overdrive 2 ms

Total Harmonic f = 1 kHz

Distortion R1 ≥ 10 kW

VO = 3 V rms –108 dB

INPUT IMPEDANCE

Differential V

= ± 1 V 1012储2 W储pF

DIFF

Common Mode 1014储2.2 W储pF

INPUT VOLTAGE RANGE

Differential

5

± 20 V
Common-Mode Voltage ± 10 ± 11 V
Over Max Operating Temperature ± 10 V
Common-Mode Rejection Ratio V

= ± 10 V 90 110 dB

CM

T

MIN–TMAX

86 100 dB

OUTPUT CHARACTERISTICS

Voltage R

Current V

≥ 2 kW VS –4 VS –2.5 V

LOAD

T

MIN–TMAX

= ± 10 V ± 5 ± 10 mA

OUT

VS –4 V

Short Circuit ± 15 mA

POWER SUPPLY

Rated Performance ± 15 V
Operating Range ± 4 ± 18 V
Quiescent Current 1.3 1.5 mA

–2–

REV. B

AD795

NOTES

1

Input offset voltage specifications are guaranteed after 5 minutes of operation at TA = +25∞C.

2

Bias current specifications are guaranteed maximum at either input after 5 minutes of operation at TA = +25∞C. For higher temperature, the current doubles every 10∞C.

3

Gain = –1, R1 = 10 kW.

4

Defined as the time required for the amplifier’s output to return to normal operation after removal of a 50% overload from the amplifier input.

5

Defined as the maximum continuous voltage between the inputs such that neither input exceeds ± 10 V from ground.

All min and max specifications are guaranteed.
Specifications subject to change without notice.

ABSOLUTE MAXIMUM RATINGS

Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ± 18 V

Internal Power Dissipation

2

(@ TA = +25∞C)

1

SOIC Package . . . . . . . . . . . . . . . . . . . . . . . . . . . . 500 mW

Input Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ± V

Output Short Circuit Duration . . . . . . . . . . . . . . . . Indefinite

Differential Input Voltage . . . . . . . . . . . . . . . . . . +V

and –V

S

Model Temperature Range Package Option*

AD795JR 0∞C to +70∞C RN-8

S

*N = Plastic mini-DIP; R = SOIC package.

S

ORDERING GUIDE

Storage Temperature Range (R) . . . . . . . . . –65∞C to +125∞C

Operating Temperature Range

AD795J . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0∞C to +70∞C

NOTES

1

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.

2

8-Pin Small Outline Package: qJA = 155∞C/Watt

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 the AD795 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.

WARNING!

ESD SENSITIVE DEVICE

REV. B

–3–

AD795–Typical Performance Characteristics

20

W

R

= 10k

L

20

R

= 10k

W

L

15

+V

IN

10

–V

IN

5

INPUT COMMON MODE RANGE – ±Volts

0

020

5

10

15

SUPPLY VOLTAGE – ±Volts

Figure 1. Common-Mode Voltage Range vs. Supply

30

Vs = ±15V

25

20

15

15

10

5

OUTPUT VOLTAGE RANGE – ±Volts

0

020

Figure 2. Output Voltage Range vs. Supply Voltage

1.0

0.95

0.90

0.85

0.80

+V

OUT

5

SUPPLY VOLTAGE – ±Volts

10

–V

OUT

15

10

5

OUTPUT VOLTAGE SWING – Volts p-p

0

10

100 1k

LOAD RESISTANCE –

W

10k

Figure 3. Output Voltage Swing vs. Load Resistance

50

SAMPLE SIZE = 1058

40

30

20

PERCENTAGE OF UNITS

10

0

0

INPUT BIAS CURRENT – pA

1.51.5

2

Figure 5. Typical Distribution of Input Bias Current

0.75

0.70

INPUT BIAS CURRENT – pA

0.65

0.60
0

5

SUPPLY VOLTAGE – ±Volts

1510

Figure 4. Input Bias Current vs. Supply

–9

10

–10

10

–11

10

–12

10

–13

INPUT BIAS CURRENT – Amps

10

–14

10

–60

–40

TEMPERATURE – °C

120100806040200–20

Figure 6. Input Bias Current vs. Temperature

20

140

REV. B–4–

DIFFERENTIAL INPUT VOLTAGE – ±Volts

INPUT BIAS CURRENT – Amperes

–6

–5

–4 –3

–2 –1

0

12

4

–I

IN

+I

IN

563

10

–4

10

–5

10

–6

10

–7

10

–8

10

–9

10

–10

10

–11

10

–12

10

–13

10

–14

VOLTAGE NOISE – mV p-p

SOURCE RESISTANCE – W

1k

10

1.0

10

3

10

4

10

9

10

8

10

7

10

6

10

5

Noise Bandwidth: 0.1 to 10Hz

100

1.00

0.95

0.90

0.85

0.80

0.75

0.70

INPUT BIAS CURRENT – pA

0.65

AD795

0.60
–10–15

–5

COMMON MODE VOLTAGE – Volts

0

+10+5

+15

Figure 7. Input Bias Current vs. Common-Mode Voltage

140

100

10

1.0

0.1

0.01

CURRENT NOISE – fA/÷Hz

15

f = 1kHz

12.5

10

VOLTAGE NOISE – nV/÷Hz

7.5

5

–60

–40

VOLTAGE NOISE

–20

CURRENT NOISE

100 120806040200

TEMPERATURE – °C

Figure 9. Voltage and Current Noise Spectral Density vs.
Temperature

Figure 8. Input Bias Current vs. Differential Input Voltage

Figure 10. Input Voltage Noise vs. Source Resistance

50

40

30

REV. B

20

PERCENTAGE OF UNITS

10

0

Figure 11. Typical Distribution of Input Voltage Noise

SAMPLE SIZE = 344

0

0.1 TO 10Hz INPUT VOLTAGE NOISE p-p – mV

f = 0.1 TO 10Hz

21

1k

100

10

VOLTAGE NOISE (REFERRED TO INPUT) – nV/÷Hz

1.0

3

110 10M1M100k10k1k100

FREQUENCY – Hz

Figure 12. Input Voltage Noise Spectral Density

–5–