AMPLITUDE DETECTION CIRCUIT

PROBLEM TO BE SOLVED: To improve the temperature characteristic of the circuit that detects an amplitude of an input signal without considerable increase in the circuit scale. SOLUTION: This circuit includes a current generating circuit 10 that generates a current corresponding to a level appearing at a common node 9 of a differential amplifier 3 amplifying an input signal and detects an amplitude of the input signal based on a current IRSSI generated by the current generating circuit 10. In this case, the current generating circuit 10 is configured with a transistor(TR) Q12 that uses the current IRSSI as a collector current, a common node 9 of the differential amplifier 3 is connected to an emitter of the TR Q12 via a resistor R8 and a level generated by using a current that increases nearly proportional to the absolute temperature is given to its base.