Variable gain amplifier circuitry in automatic gain control

摘要

A variable gain amplifier (VGA) circuitry for implementing gain as a pseudo exponential function by using the linear area of metal oxide semiconductor field effect transistors (MOSFETs) is provided. The VGA circuitry includes a fixed resistor and a variable resistor, which is connected in serial to the fixed resistor and implemented by combining one or more MOSFETs operating in a linear area with different control voltages to each MOSFET. Although the MOSFET has no exponential characteristics, the VGA circuitry can easily implement a pseudo exponential function with a simple structure. Further, since a complex circuit for generating an exponential function is not necessary, power consumption thereof can be eliminated.