AMPLIFIER

PURPOSE:To display the saturating state of an amplifier by providing a diode and a transistor (TR) for detecting the saturated state between a base and a collector of the TR at the 2nd stage of a multi-stage amplifier circuit and lighting a light emitting diode with this output. CONSTITUTION:When TRs 7, 8 being an output stage are saturated, a signal fed back from negative feedback circuits 9-12 to a TR3 becomes a clip signal and a differential input of TRs 2, 3 is increased. Further, the differential output is increased, a TR4 is over-driven and saturated, its collector potential is lower than the base potential and a diode 18 and a TR19 for detecting the saturated state are turned on. As a result, a current flows to a resistor 20, and a potential difference across the resistor 20 operates TRs 21, 25 so as to light a light emitting diode 26. Since the saturation of the amplifier is known through the lighting, the input level is set easily.