Voltage Controlled Amplifiers or Variable Gain Amplifiers are electronic differential amplifiers. VCA or VGA will vary their gain depending on a control voltage. You can control the gain by using a single DC voltage input pin. The voltage controlled amplifier will operate in many frequency bands.Voltage control amplifier applications: Audio level compression, synthesisers and amplitude modulation. RF/IF AGC amplifiers (automatic gain control), video gain controls, signal measurements, cellular/PCS base stations, IF sampling receivers, fixed wireless access and Instrumentation.