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Peak Selection and Detection Circuit

IP.com Disclosure Number: IPCOM000092194D
Original Publication Date: 1968-Oct-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 39K

Publishing Venue

IBM

Related People

Wilford, CR: AUTHOR

Abstract

This circuit separates one selected voltage peak from a plurality of peaks and provides an output voltage representing the amplitude of that peak. The circuit of drawing 1 is arranged to select the +Va peaks from a set of repetitively occurring peaks in the input waveform Vin of drawing 2. The sequence and polarities of the individual peaks in the set remain unchanged.

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Peak Selection and Detection Circuit

This circuit separates one selected voltage peak from a plurality of peaks and provides an output voltage representing the amplitude of that peak. The circuit of drawing 1 is arranged to select the +Va peaks from a set of repetitively occurring peaks in the input waveform Vin of drawing 2. The sequence and polarities of the individual peaks in the set remain unchanged.

Integrating network R3C3 provides the average DC voltage of the input waveform, which should be 0 volts, at the base of transistor Q3. As the input voltage goes positive to +Va, the voltage of node P1 follows it. When node P1 becomes more positive than the baseline of Vin, Q3 turns on and transistor Q2 turns off. Q2 thus turns transistor Q1 off. Diode D3, previously back-biased, becomes forward-biased and provides a high current, low impedance path from voltage source V2 through resistance R4 for charging capacitors C1 and C2 to the peak voltage amplitude of peak +Va. The voltage of C2 and hence of the peak is supplied at output Vo.

The voltage at P1 follows the voltage of input Vin down to -Va and down to - Vb, but C2 does not discharge to those voltages because diode D2 is back- biased. Hence, Vo remains at the voltage of C2 which only discharges very slowly from peak +Va through resistor R2. As node P1 goes more negative than the output of network R3C3, Q2 conducts, turning Q1 on, thus back-biasing D3. Vin then goes up to peak +Vb, but node P1 cannot follow b...