REV. D

OP497

–8–

OPEN-LOOP GAIN LINEARITY

The OP497 has both an extremely high gain of 2000 V/mv mini-

mum and constant gain linearity. This enhances the precision of

the OP497 and provides for very high accuracy in high closed-loop

gain applications. Figure 5 illustrates the typical open-loop gain

linearity of the OP 497 over the military temperature range.

15

–10

–15

10

5

0

–5

OUTPUT VOLTAGE – Volts

15V

Figure 5. Open-Loop Linearity of the OP497

APPLICATIONS

Precision Absolute Value Amplifier

The circuit of Figure 6 is a precision absolute value amplifier

with an input impedance of 30 M

Ω. The high gain and low

input signals. In this circuit, the input always appears as a com-

mon-mode signal to the op amps. The CMR of the OP497

exceeds 120 dB, yielding an error of less than 2 ppm.

+15V

2

3

–15V

4

C3

0.1 F

8

1

6

5

7

0V < V

< 10V

OUT

D1

1N4148

R3

1k

R1

1k

C2

0.1 F

C1

30pF

D2

1N4148

R2

2k

1/4

OP497

1/4

OP497

Figure 6. Precision Absolute Value Amplifier

PRECISION CURRENT PUMP

Maximum output current of the precision current pump shown

in Figure 7 is

±10 mA. Voltage compliance is ±10 V with ±15 V

supplies. Output impedance of the current transmitter exceeds

3 M

Ω with linearity better than 16 bits.

2

3

1

7

8

5

6

4

–15V

+15V

10mA

–

+

VIN

=

= 10mA/ V

R5

100

R1

10k

R2

10k

R4

10k

R3

10k

R5

10k

1/4

OP497

1/4

OP497

Figure 7. Precision Current Pump

PRECISION POSITIVE PEAK DETECTOR

In Figure 8, the CH must be of polystyrene, Teflon

*, or polyeth-

ylene to minimize dielectric absorption and leakage. The droop

rate is determined by the size of CH and the bias current of the

OP497.

2

3

1

7

8

5

6

4

–15V

+15V

1N4148

2N930

RESET

1k

1k

1k

1k

0.1 F

0.1 F

1/4

OP497

1/4

OP497

Figure 8. Precision Positive Peak Detector

SIMPLE BRIDGE CONDITIONING AMPLIFIER

Figure 9 shows a simple bridge conditioning amplifier using

the OP497. The transfer function is:

VV

R

RR

R

R

OUT

REF

F

=

+









∆

∆

The REF43 provides an accurate and stable reference voltage

should be 0.1% or better with a low temperature coefficient.

*Teflon is a registered trademark of the Dupont Company.