AD542 View Datasheet(PDF) - Analog Devices

Part Name

Description

Manufacturer

AD542

High Performance/ BiFET Operational Amplifiers

Analog Devices 

AD542/AD544/AD547

This particular log ratio circuit is free from the dynamic prob-

lems that plague many other log circuits. The –3 dB bandwidth

is 50 kHz over the top 3 decades, 100 nA to 100 µA, and de-

creases smoothly at lower input levels. This circuit needs no ad-

ditional frequency compensation for stable operation from

input current sources, such as photodiodes, that may have 100

pF of shunt capacitance. For larger input capacitances a 20 pF

integration capacitor around each amplifier will provide a

smoother frequency response.

This log ratio amplifier can be readily adjusted for optimum

accuracy by following this simple procedure. First, apply V1 =

V2 = –10.00 V and adjust “Balance” for VOUT = 0.00 V. Next

apply V1 = –10.00 V, V2 = –1.00 V and adjust gain for VOUT =

+1.00 V. Repeat this procedure until gain and balance readings

are within 2 mV of ideal values.

Figure 34. Differentiator

Figure 35. Low Drift Integrator and

Low Leakage Guarded Reset

Figure 36. Wien-Bridge

Oscillator–fO = 10 kHz

Figure 37. Capacitance

Multiplier

Figure 38. Long Interval

Timer–1,000 Seconds

Figure 39. Positive Peak Detector

–10–

REV. B

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