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Peak Detector

IP.com Disclosure Number: IPCOM000077073D
Original Publication Date: 1972-Jun-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 41K

Publishing Venue

IBM

Related People

Arnold, RW: AUTHOR

Abstract

Transistors PQ1, PQ2, PQ3 and associated components form a unity gain amplifier to provide a high-input impedance, and a low-output impedance. Resistors PR1 and PR2 attenuate the input signal. Transistors PQ4, PQ5, diodes PD6, PD7, PD8 and capacitor PC2 form a differentiator. The unity gain amplifier PQ3 drives capacitor PC2. The current in the capacitor is equal to de/dt. Therefore, if de/dt is positive or negative so is the current in PC2. This current then flows in PD7 or PD8 depending on the direction of the current. Transistors PD4 and PD5 form a shunt feedback amplifier for diodes PD7 and PD8. For a sinewave input, as de/dt goes from positive to negative (and therefore through a peak) the current goes from diode PD7 to diode PD8. This produces a positive voltage change on the collector of PQ5.

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Peak Detector

Transistors PQ1, PQ2, PQ3 and associated components form a unity gain amplifier to provide a high-input impedance, and a low-output impedance. Resistors PR1 and PR2 attenuate the input signal. Transistors PQ4, PQ5, diodes PD6, PD7, PD8 and capacitor PC2 form a differentiator. The unity gain amplifier PQ3 drives capacitor PC2. The current in the capacitor is equal to de/dt. Therefore, if de/dt is positive or negative so is the current in PC2. This current then flows in PD7 or PD8 depending on the direction of the current. Transistors PD4 and PD5 form a shunt feedback amplifier for diodes PD7 and PD8. For a sinewave input, as de/dt goes from positive to negative (and therefore through a peak) the current goes from diode PD7 to diode PD8. This produces a positive voltage change on the collector of PQ5. Where de/dt is negative and goes positive, there is a negative voltage change on the collector of PQ5. These voltage changes are fed to transistors PQ6 and PQ8. Transistor PQ6 serves as an emitter-follower and drives transistor PQ7. Transistor PQ7 is normally on. If a negative peak is present, the emitter of PQ6 goes negative and is capacitively coupled to the base of PQ7 turning it off for a period of time as determined by the PR21, PC5 time constant. Transistor PQ7 indicates negative peaks when its output is switched positive. Transistor PQ8 serves as a shunt feedback stage with a voltage gain of -1. Transistor PQ9 operates identical to PQ7, except its...