LOGIC CIRCUIT FOR CONTROLLING OUTPUT TO BE HIGH

PURPOSE:To warrant an output terminal to be kept for a high impedance with the logic circuit capable of controlling its output to be in a high impedance state with a control input signal. CONSTITUTION:At application of power where an operating voltage is applied to a power supply terminal of an output high impedance logic circuit, a logic level at a control input stage is not certain and transistors(TRs) 11, 12 are conductive, but the nonconductive state of a TR 14 connecting to a collector of the TR 12 is kept till the applied power supply voltage reaches a threshold voltage of the MOS TR. Thus, no current is absorbed by an output terminal and the output terminal is warranted to be in the high impedance state.