Open-Loop Peak Detector Circuit

In this open-loop design, the detector diode is Dl, and a level shifting or compensating diode is D2. Load resistor RL is connected to -5 V, and an identical bias resistor RL is connected to -5 V, and identical bias resistor RB is used to bias the compensating diode. Resistors with equal values ensure that the diode drops are equal. Low values of RL and RB (1 kU to 10 kf2) provide fast response, but at the expense of poor low-frequency accuracy. High values of RL and Rn provide good low-frequency accuracy, but cause the amplifier to slew rate limit, resulting in poor high-frequency accuracy.
Open-Loop Peak Detector Circuit - schematic

A good compromise can be made by adding a feedback capacitor CFB, which enhances the negative slew rate on the (-) input.

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