Patent ID: 6239625
Filing Date: 2001-05-29
Classification: H03D

Abstract:
A detection circuit for detecting an envelope of an input signal having a predetermined frequency, comprising:a field effect transistor including a gate, a drain, and a source, to the gate of which the input signal is input through a coupling capacitor having a negligible impedance at said predetermined frequency,a gate bias circuit means for providing a gate bias voltage to the gate of the field effect transistor,a voltage source connected between an element in said gate bias circuit means and a source of reference potential,a coupling capacitor connected between the drain of the field effect transistor and the ground and having a negligible resistance at said predetermined frequency,a drain bias circuit means providing a drain bias to the drain of the field effect transistor,a second voltage source providing a voltage to an element of said drain bias circuit means, anda load capacitor and a load resistor connected in parallel between the source of the field effect transistor and the ground,wherein a detection signal corresponding to the envelope of the input signal is output from the source of the field effect transistor.