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Peak Detector

IP.com Disclosure Number: IPCOM000078429D
Original Publication Date: 1973-Jan-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 2 page(s) / 28K

Publishing Venue

IBM

Related People

Ristad, CH: AUTHOR

Abstract

This AC peak detector is less sensitive to noise, less dependent on frequency by avoiding differentiation of input signals, and can detect successive peaks of varying absolute amplitude.

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Peak Detector

This AC peak detector is less sensitive to noise, less dependent on frequency by avoiding differentiation of input signals, and can detect successive peaks of varying absolute amplitude.

A positive-going waveform at the input causes capacitor C1 to charge through diode D1. After the input waveform reaches a Peak and starts going negative, the capacitor is discharged through diode D2 and resistor R1. The negative voltage developed across R1 is applied to the "-" input of the comparator. When this voltage becomes more negative than the negative reference voltage at the "+" input, the comparator switches from a low to a high level which causes the single-shot to generate a pulse at the output. In this way a pulse is generated for each peak of the waveform.

Because of the action of diode D2, the voltage at the "-" input will never become positive. Therefore, the reference voltage at the "+" input should be kept from going positive or the comparator will latch up. Resistor R3 places a small negative potential at the "+" input of the comparator which prevents latching up, and also establishes a noise rejection threshold. The circuit will reject noise which is lower than the sum of the diode drop across diode D2, and the negative reference voltage at the "+" input. Resistor R4 introduces hysteresis which further improves noise rejection.

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