REV. C

OP77

–12–

RR

R

54

2

+

must =

R

R

3

1

Precision Current Sinks

OP77

V+

200

R1

1

1W

IRF520

FULL SCALE OF 1V,

1A/V

R1

Figure 11. Positive Current Sink

OP77

V–

200

R1

IRF520

R1

Figure 12. Positive Current Source

These simple high-current sinks require the load to float between

the power supply and the sink.

ensure high accuracy.

OP77

R1

1.8k

2mA

D1

1N4579A

6.4V

5%

5ppm/ C

15V

2

3

4

6

7

R2

R3

3.6k

6.4k

Figure 13. High Stability Voltage Reference

This simple bootstrapped voltage reference provides a precise 10 V

virtually independent of changes in power supply voltage, ambi-

ent temperature and output loading. Correct Zener operating

current of exactly 2 mA is maintained by R1, a selected 5 ppm/

∞C

resistor, connected to the regulated output. Accuracy is prima-

rily determined by three factors: the 5 ppm/

∞C temperature

coefficient of D1, 1 ppm/

∞C ratio tracking of R2 and R3, and

VOs errors, amplified by 1.6 (AVCL), appear at the output and

can be significant with most monolithic amplifiers. For example,

mV/∞C contributes 0.8 ppm/

contributes but 0.05 ppm/

∞C of output error, thus effectively

inputs from microvolts to volts. In this circuit, the signal always

OP77E

OP77E

+15V

2

3

6

7

–15V

0.1 F

C1

30pF

D1

1N4148

D2

2N4393

R3

2k

1k

4

2

3

6

7

4

0.1 F

0.1 F

0.1 F

+15V

–15V

1k

Figure 14. Precision Absolute Value Amplifier

inputs from microvolts to volts. In this circuit, the signal always

appears as a common-mode signal to the op amps. The OP77E

CMRR of 1

V/V assures errors of less than 2 ppm.