To apply an amplifier even in a high frequency range and also to amplify the signals of various levels up to large electric power by using an electrostatic induction transistor that excels in the frequency characteristic as a cascade connection circuit.

In a cascade connection circuit, a gate grounded circuit of a SIT(electrostatic induction transistor) is connected to the next stage of a source grounded circuit. In such a constitution, the negative bias is applied to the gate of the SIT of the preceding stage to secure the OFF characteristic for an entire circuit due to the normally ON characteristic of the SIT. The negative bias value is effective at about -5V. At the same time, another cascade connection circuit where a gate grounded circuit of the SIT is connected to the next stage of a source grounded circuit of an FET(field effect transistor) is also available. In such cases, the normally ON characteristic is secured for an entire circuit with use of the FET and no negative bias is needed.