US Patent 7911274 Variable transconductance circuit

The variable transconductance circuit includes: a voltage-current conversion circuit for outputting a current signal linear with an input voltage signal; first and second MOS transistors for converting the current signal received to a square-root compressed voltage signal; and third and fourth MOS transistors for converting the square-root compressed voltage signal to a linear current signal. A bias current at the first and second MOS transistors and a bias current at the third and fourth MOS transistors are varied to control transconductance.