An adder adds a noise signal, an input signal, and a feedback signal. A threshold determination unit compares an addition signal output from the adder with a predetermined threshold, and outputs an ignition pulse signal. A transient response unit causes transient response of the ignition pulse signal, and generates an output signal. An intensity adjustment unit is formed of a variable resistor provided on a feedback loop, adjusts intensity of the feedback signal, and inputs the feedback signal to the adder.