Voltage Controlled Gain Video Amplifier
Gain adjustment will be more flexible if it controlled by a voltage signal, since we can use many methods to provide user interface. We can control it by a potentiometer with anti glitch filter, or we can drive it with DAC from digital controller. On the circuit depicted in the following schematic diagram, we use silicon diodes to vary the gain of a wide-band video amplifier over 2 to 32 db range. The bandwidth is almost remain constant at 12 Mc and input impedance constant at 10 Kohm.