Amplifying electronic circuit with stable idling current

Abstract

The semiconductor types of first and second semiconductor type transistors are different from one another and the two transistors are connected in series. An input signal is supplied to each of the bases of the first and second transistors. Each of the collector electric currents of the first and second transistors are thus controlled. An output is provided from the inter-connection point of the first and second transistors. A third transistor supplies the collector electric current which is 1/K.sub.1 times the collector electric current of the second transistor, where K.sub.1 is the current-mirror ratio between the second and third transistors. A fourth transistor has the collector and base connected with one another. The fourth transistor supplies an electric current according to the collector electric current of the third transistor. A fifth transistor has the base electric current controlled by the base electric current of the fourth transistor. The fifth transistor supplies its collector electric current, which is K.sub.2 times the collector electric current of the fourth transistor, to the base of the first transistor, where K.sub.2 is the current-mirror ratio between the fourth and fifth transistors.