| 摘要 |
<p>PURPOSE:To obtain a zero-cross Schmitt circuit without fluctuation of the threshold voltage from the zero-crossing at the inversion of an output signal, by prviding transistors (TRs) to a bias circuit at an input terminal of a differential amplifier. CONSTITUTION:At the period of T1 when a power supply voltage is applied between terminals 2 and 4 and no input signal is given to a terminal 1, base potentials VC and VD of TRs Q2 and Q3 of a differential amplifier are equal to each other. At the period of T2, where an input signal is applied to the terminal 1, since VC>=VD is always established, an output signal outputted to a terminal 3 goes to a high level. At the period T3, since a Q7 is nonconductive from VC=VD to VC<VD, an output signal at the terminal 3 goes to a low level. At the period T4, the Q7 is conductive at a point where the voltage changes from VC<VD to VC=VD, the potential of the VD is restored to the potential at the periods T1 and T2 and the output signal of the terminal 3 goes to a high level. The threshold voltage where the output signal is inverted from the low to the high level, can not be fluctuated with R5=R6 and R6=R7.</p> |
