Peak Detector Circuit Explained

In this video, the peak detector circuits have been explained.

By watching this video you will learn the following topics:

0:20 How to Design the peak detector circuit (Using Diode and capacitor) and its working

2:29 Precision peak detector Circuit

3:05 Effect of load on the peak detector circuit

4:26 Precision peak detector Circuit with Buffer

5:16 Modified Peak detector circuit for the fast signals (High-Speed Peak Detector)

What is a peak detector circuit:
The peak detector circuit is used to measure the peak value of the signal.

The simple peak detector circuit can be designed using the diode and capacitor. But because of the voltage drop across the diode, this circuit will not measure the peak value of the signal accurately.

To measure the peak value of the signal accurately, precision peak detector (active peak detector) circuit is used.

Precision Peak Detector:
In Precision peak detector circuit, super diode or precision diode is used instead of the normal signal diode.
And the capacitor is connected to the output of the super diode.

Effect of load on the peak detector circuit:

Ideally, the capacitor of the peak detector should hold the peak voltage of the signal. But because of the finite load across the capacitor, the capacitor will get discharged through the load. And gradually the voltage held by the capacitor will reduce.

To, minimize the discharging of the capacitor the RC time constant should be very large (At least 10 times more than the time period of the signal)

And the best practice is to use the buffer circuit before connecting the peak detector circuit to some other circuit.

Modified Precision Peak Detector circuit for fast signals:

The precision peak detector will not work at high frequency. Because when the diode becomes reversed biased, the op-amp goes into the negative saturation. And that restricts the operating frequency range of the circuit. Using a modified circuit, it can be used for the fast signal as well.
For very fast signal, Schottky diodes are used instead of signal diodes.

This video will be helpful to all students of science and engineering in understanding the working of the peak detector and the precision peak detector circuit.

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