| 摘要 |
PROBLEM TO BE SOLVED: To provide an electrostatic protection circuit wherein the dielectric breakdown of the gate of an input transistor is prevented for improved electrostatic resistance with no drop in frequency band nor significant increase in input leakage current, related to an input circuit of a compound semiconductor integrated circuit using an MESFET. SOLUTION: A source and drain of a protective transistor 2 comprising a normally-on field effect transistor are connected, for releasing static electricity, to a gate and source or ground terminal of an input transistor 5 of an input circuit comprising a differential amplifying circuit or source follower circuit comprising a field effect transistor such as MESFET. Meanwhile, in the normal operation state of the input circuit, its gate is connected to a low electric potential such as ground electric potential so that its protective transistor comes to off state, constituting an electrostatic protection circuit.
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