AMPLIFIER FOR VIDEO SIGNAL

摘要

PURPOSE:To detect a minute signal with high S/N by excluding a carrier signal component with a prescribed amplitude having no signal on and amplifying the component at a tuning amplifier. CONSTITUTION:An image sensor 1 is driven by a clock from a clock generating circuit 2, a video signal S1 synchronized with the clock is turned to a video frequency by a resonance circuit 5 to be a signal S' comprising a carrier signal component Va with a prescribed amplitude with no signal on and a detection signal component Vs. A signal tuned to the video frequency from a tuning amplifier circuit 3 is inputted to a voltage division circuit 4, the level of an output signal S2' of a resonance circuit 6 is adjusted by a variable resistor Rv so as to be a level almost equal to the carrier signal component Va of the signal S1'. A subtraction circuit 7 subtracts the signal S2' from the signal S1' and an output signal S5 becomes a signal with higher S/N than that of the signal S1. The signal S5 is amplified by a tuning amplifier circuit 8 and is subject to envelope detection by a detection circuit 9.