Frequency-to-voltage converter

Abstract

A sample-and-hold circuit samples an incoming alternating signal to provide a voltage proportional to input frequency of a sinusoidal signal. A Schmitt trigger circuit and a divide-by-two multivibrator convert the sinusoidal input signal into two square wave signals separated in phase by 180* and each corresponding to the previous full cycle of the input to provide sampling signals to a pair of sample-and-hold circuits. Each sample-and-hold circuit samples the opposite half cycle or period of a corresponding square wave. Transistor means are connected to the corresponding timing circuit to discharge a voltage storage means prior to sampling in response to the start of the sampling half period. Each sample-and-hold circuit includes a transistor selectively charging the voltage storage means from a constant voltage source during the sampling half period to produce a voltage level related to the input frequency which voltage level is held during the non-sampling half period. Analog switches are connected to the circuits and alternately connect each circuit to an output amplifier to apply the hold voltage during the nonsampling half period.