Level Control and Special Circuits
Douglas Self · Focal Press eBooks · 2020
A circuit block that gives voltage-control of gain is a difficult thing to implement. The basic function is simply that of multiplication, but most of the practical techniques introduce significant distortion. An operational transconductance amplifier (OTA) gives a current output for a voltage difference input, and the amount of current you get for a given input voltage is determined by the current that is made to flow into a control port, giving a variable-gain capability. The difficulty of implementing a good voltage-variable gain element is testified to by the number of technologies that have been tried. An OTA gives a current output for a voltage difference input, and the amount of current you get for a given input voltage is determined by the current that is made to flow into a control port, giving a variable-gain capability. Voltage-controlled amplifier is the name given to a specific kind of variable-gain device.