PURPOSE:To avoid a change of an output waveform due to the power supply voltage and at the same time to receive no effect of the temperature dependence of base-emitter voltage VBE of a transistor, by setting the output of a transistor pair having a common emitter at an integer-fold value of the VBE. CONSTITUTION:A current I0=VBE/R13 is supplied to an emitter-coupled logical circuit consisting of transistors TRQ12 and TRQ13 from constant current circuits Q10, Q11, Q14 and R10. The signal passed through emitter follower TRQ15 and TRQ16 is divided by resistances R13-R16, and the inputs of TRQ18 and TRQ19 are set as VIH={(VCC-2VBE)R16/(R15+R16)}+VBE. Therefore the current I1 of the TRQ18 and TRQ19 is set as I1=(VIH-VBE)/R19=(VCC-2VBE) R16/ R19(R15+R16). The output of the TRQ19is supplied to TTL level converting circuits Q20-Q25. A low level V2L of the output of the TRQ19 is set as V2L=2VBE if the resistance value is selected so as to satisfy R16R15=R19(R15+R16) and therefore receives no effect of power supply voltage.
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