ANALOG DEVICES AD795 Service Manual

Low Power, Low Noise

–V

FEATURES

Low power replacement for Burr-Brown

OPA111, OPA121 op amps

Low noise

3.3 μV p-p maximum, 0.1 Hz to 10 Hz
11 nV/√Hz maximum at 10 kHz

0.6 fA/√Hz at 1 kHz

High dc accuracy

500 μV maximum offset voltage
10 μV/°C maximum drift
2 pA maximum input bias current
Low power: 1.5 mA maximum supply current

APPLICATIONS

Low noise photodiode preamps
CT scanners
Precision l-to-V converters

GENERAL 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 FET­input device. The 10
that input bias current is essentially independent of common­mode voltage and supply voltage variations.

The AD795 has both excellent dc performance and a guaranteed
and tested maximum input voltage noise. It features 2 pA
maximum input bias current and 500 μV maximum offset
voltage, along with low supply current of 1.5 mA maximum.

1k

14

Ω common-mode impedance insures

Precision FET Op Amp

AD795

CONNECTION DIAGRAM

NC

1

2

–IN

+IN

3

4

S

AD795

NC = NO CO NNECT

Figure 1. 8-Lead SOIC (R) Package

Furthermore, the AD795 features a guaranteed low input noise
of 3.3 μV p-p (0.1 Hz to 10 Hz) and a 11 nV/√Hz maximum
noise level at 10 kHz. The AD795 has a fully specified and
tested input offset voltage drift of only 10 μV/°C maximum.

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

The AD795 is available in an 8-lead SOIC package.

50

SAMPLE SIZE = 570

40

NC

8

+V

7

OUTPUT

6

5

NC

S

00845-001

30

100

20

PERCENTAGE OF UNITS

10

VOLTAGE NOISE SPE CTRAL DENSIT Y (nV/ Hz)

1

10 100 1k 10k

Figure 2. Voltage Noise Spectral Density

FREQUENCY (Hz)

00845-002

10

0

–5 –4 –3 –2 –1 0 1 2 3 4 5

Figure 3. Typical Distribution of Average Input Offset Voltage Drift

INPUT OFFSET VOLTAGE DRIFT (µV/°C)

00845-003

Rev. C

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