Exponential function generator implemented by CMOS process and variable gain amplifier using the same

摘要

PURPOSE: An exponential function generator formed by a CMOS process and a variable gain amplifier using the same are provided to reduce a manufacturing cost and increase a degree of integration by forming the exponential function generator with the CMOS process. CONSTITUTION: A variable gain amplifier includes an input portion(710), an exponential function generation portion, a control current generation portion(730), and one or variable voltage amplification portions(740A,740B). The input portion amplifies a differential input signal to a fixed gain value and outputs the amplified signal as a voltage level. The exponential function generation portion outputs a signal having an approximate exponential function value by adding outputs of the first and the second curve generation portions. The control current generation portion generates the exponential control current in response to an output voltage of the exponential function generation portion. The variable voltage amplification portions perform a variable gain amplification operation for the output voltage of the input portion in response to the control current.