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Differentiator and Rectifier

IP.com Disclosure Number: IPCOM000080103D
Original Publication Date: 1973-Oct-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 33K

Publishing Venue

IBM

Related People

Commander, RD: AUTHOR

Abstract

The circuit shown is designed to derive a current waveform by differentiation of a generally triangular input waveform. A differentiating capacitor C is arranged in a feedback network between a pair of driver rectifier circuits T1 D1, T3 D3 and respective inputs of an operational amplifier, whose output drives one of the driver rectifier circuits. The input of the other driver rectifier is held at a fixed DC potential.

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Differentiator and Rectifier

The circuit shown is designed to derive a current waveform by differentiation of a generally triangular input waveform. A differentiating capacitor C is arranged in a feedback network between a pair of driver rectifier circuits T1 D1, T3 D3 and respective inputs of an operational amplifier, whose output drives one of the driver rectifier circuits. The input of the other driver rectifier is held at a fixed DC potential.

The arrangement is such that essentially all current flowing through the capacitor C is supplied by the driver rectifiers, the feedback paths being buffered by emitter-follower circuits. Thus although the circuit is basically unbalanced, in that the voltage across the capacitor C and in the driver rectifier circuit has a common mode level of about half the differential signal, the feedback network R1, R2, R3 and R4 ensures that the desired differential voltage appears across the capacitor C. The capacitor is effectively push-pull driven by the two driver transistors, and the rectified current output appears at the collectors of the two driver transistors.

A resistor R8 is included in series with capacitor C to provide a high frequency roll-off for the differentiator.

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