Russell H Poulson

US Patent:

41662482, Aug 28, 1979

Filed:

Nov 25, 1977

Appl. No.:

5/854880

Inventors:

Frank J. Bianchi - Redford Township, Wayne County MI
Russell H. Poulson - Dearborn Heights MI

Assignee:

Ford Motor Company - Dearborn MI

International Classification:

H03K 114

US Classification:

328140

Abstract:

A sample and hold frequency to voltage converter circuit particularly suitable for use in automotive applications as a tachometer or other speed indicating device. The converter uses circuit means, responsive to a periodically varying input signal, to generate first and second pulse trains. The pulses in the pulse trains have a repetition frequency and duty cycle that varies as a function of the frequency of the input signal. An integrator is provided for generating a voltage proportional to the duty cycle of the second pulse train. A transmission gate is controlled by the first pulse train and couples the integrator to a capacitor. The capacitor is charged or discharged, almost instantaneously, each time the transmission gate is rendered conductive by a pulse from the first pulse train. The capacitor then develops a voltage which is proportional to the frequency of the input signal.