High-Speed Frequency-to-Voltage Converter with 0.01-Percent Accuracy

A frequency-to-voltage converter is described, for use as a control circuit in a voltage-controlled oscillator with a 100-kHz central frequency, varying within an octave on either side. Conversion is effected by averaging standard pulses of constant width and constant height, corresponding to the zero cross of each cycle of the measured frequency. Accuracy of 0.01 percent and better is secured by determining the pulsewidth by an exact digital system and determining the pulseheight by switching an exact current source. The range of measurement and response time may be varied by the user in accordance with his optimization requirements.