Low-noise video preamplifier

摘要

For reduction of the relative noise amplitude a modulator or chopper stage is provided in front of the input of a video preamplifier and at the preamplifier output balanced demodulators are provided with a subtraction circuit combining their outputs. Preferably the carrier wave used for chopping or modulation is applied to the demodulators for synchronous demodulation, with a phase shifter if necessary in the carrier supplied to the demodulators for compensation of the signal propogation time through the preamplifier.