Abstract: An output circuit of an amplifier which does not change power consumption. Since the output circuit of the amplifier does not flow, to a power supply circuit, a current correlated to a signal, the output circuit is not affected by the power supply circuit. The output circuit of the amplifier is provided with: a three-terminal amplifying element having an input terminal, an output terminal, and a common terminal; and a constant current circuit which is connected to the common terminal, and which flows a substantially constant current to the three-terminal amplifying element. The output terminal is grounded, and amplified output is taken out between the output terminal, and a contact point between the common terminal and the constant current circuit. Thus, the consumption current of the output circuit of the amplifier is merely the current flowing in the constant current circuit.