CIRCUIT OF GENERATING GAIN CONTROL SIGNALS

摘要

PURPOSE: A circuit of generating gain control signals is provided to adjust the range of voltage gain to a changed process and to use otherwise unnecessarily consumed current as constant current source. CONSTITUTION: A circuit of generating gain control signal includes two sections of differential amplification(110) and output(130). The section of differential amplification(110) compares a reference voltage(Vref) and an externally given control voltage(Vctrl) and generates a current(lx) corresponding to the difference between the voltages(Vref,Vctrl). The output section(130) receives the current(lx) from section of differential amplification(110) and generates a gain control signal(AGC_OUT). Here, the circuit prevents the change of gains by compensating the change with an external tuning voltage(Tuning). A current mirror of a transistor(144) uses current(lb) otherwise unnecessary as a reference current(lref) of the circuit.