PURPOSE:To make the titled inverter stable in operation even its input terminal is opened by connecting equivalently the input terminal to a power supply via a resistor to as to bring the level of the input to 'H' level. CONSTITUTION:A P-channel MOS transistor (TR) P1 and an N-channel MOS TR N1 constitute a complementary inverter and gates of the MOS TRs P1 and N1 are connected to an input terminal 1. P-channel MOS TRs P2 and P3 are connected in series between the power supply V (positive) and the input terminal I. Outputs of the MOS TRs P1 and N1 are connected to a gate of the MOS TR P2, which is turned on when the output of the inverter comprising the MOS TRs P1 and N1 is at 'L' level. Since the gate of the MOS TR P3 is connected to the power supply (negative side), the TR P3 is always turned on and its operation resistor R is kept connected.
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