UN DETECTOR DE UMBRAL PARA UN RECEPTOR DE FRECUENCIA VOCAL.

摘要

A threshold detector is disclosed which provides an output signal in response to a sinusoidal signal from a band pass filter while the sinusoidal signal has a voltage level equal to or above a reference voltage. The detector employs an operational amplifier as a first comparator or detector circuit to provide a pulse in response to each excursion of the sinusoidal signal above the threshold value. Current from the pulse is used to charge a capacitor in an RC circuit to a level above the reference voltage. A second operational amplifier is connected to the RC circuit to provide the desired constant output voltage so long as the stored voltage is equal to or above the reference voltage. Feedback from the output of the second operational amplifier to the input of the first operational amplifier is used to adjust the reference voltage to a level which makes the threshold detector insensitive to noise input associated with the sinusoidal signal.