output terminal i in this embodiment the collector of the transistor q 37 of the differential amplifier circuit 12 is especially connected through the load resistor r 30 to that output terminal a of the constant voltage circuit 14 which provides the voltage v cc1 still higher than the voltages v cc2 and v cc3 therefore the resistance of the load resistor r 30 can be selected so as to operate the transistor q 37 in the non saturated state and the amplitude of the output signal at the output terminal i can be made large this makes it possible to easily supply a desired voltage to a circuit 15 which utilizes the detector circuit furthermore this optimizes the operating condition of the transistor q 36 more specifically since the collector output voltage the voltage at the terminal e of the transistor q 36 having the time constant circuit 10 as its input citcuit may be a small voltage enough to drive a positive feedback circuit for example 1 10 of the voltage at the terminal i the transistor q 36 can be operated in a sufficiently unsaturated state as a result even when the base input voltage of the transistor q 36 becomes high in the transient state at the turn on of the transistor q 36 it does not rise above the collector voltage of the transistor q 36 and does not bring the transistor q 36 into saturated operation in this manner it is.