A Fast-Acting Feedback Loop for Pulse Amplitude Ratio Measurement

Design and operating details of a voltage ratio measuring circuit are presented. The circuit employs a wide bandwidth function multiplier as a variable gain amplifier. The denominator voltage activates a feedback loop causing multiplier gain adjustment. Adjustment proceeds until the multiplier output is equal to a Zener reference voltage. The multiplier gain is then equal to the ratio of Zener reference voltage to denominator voltage. Multiplier gain is stored by an integrator serving as a memory. The numerator voltage does not activate the feedback loop, but is simply amplified by the multiplier. The resulting output voltage is the ratio of the input voltages referred to a Zener reference. Null-balance time of 5 μS allows ratio measurement of 16-kc pulse pairs.