OP97

Rev. G | Page 11 of 16

APPLICATION INFORMATION

The OP97 is a low power alternative to the industry-standard

precision op amp, the OP07. The OP97 can be substituted

directly into OP07, OP77, AD725, and PM1012 sockets with

improved performance and/or less power dissipation and can be

inserted into sockets conforming to the 741 pinout if nulling

circuitry is not used. Generally, nulling circuitry used with earlier

generation amplifiers is rendered superfluous by the extremely

low offset voltage of the OP97 and can be removed without

compromising circuit performance.

Extremely low bias current over the full military temperature

range makes the OP97 attractive for use in sample-and-hold

amplifiers, peak detectors, and log amplifiers that must operate

over a wide temperature range. Balancing input resistances is

not necessary with the OP97. Offset voltage and TCVOS are

degraded only minimally by high source resistance, even when

unbalanced.

The input pins of the OP97 are protected against large

differential voltage by back-to-back diodes. Current-limiting

resistors are not used to maintain low noise performance. If

differential voltages above ±1 V are expected at the inputs,

series resistors must be used to limit the current flow to a

maximum of 10 mA. Common-mode voltages at the inputs are

not restricted and may vary over the full range of the supply

voltages used.

The OP97 requires very little operating headroom about the

supply rails and is specified for operation with supplies as low as

±2 V. Typically, the common-mode range extends to within 1 V

of either rail. The output typically swings to within 1 V of the

rails when using a 10 kΩ load.

Offset nulling is achieved utilizing the same circuitry as an

OP07. A potentiometer between 5 kΩ and 100 kΩ is connected

between Pin 1 and Pin 8 with the wiper connected to the

positive supply. The trim range is between 300 μV and 850 μV,

depending upon the internal trimming of the device.

8

4

7

5

3

6

2

1

OP97

–V

COC

+V

RPOT = 5kΩ TO 100kΩ

Figure 29. Optional Input Offset Voltage Nulling

and Overcompensation Circuit