| 摘要 |
PURPOSE:To obtain the sufficiently large and stable hysteresis width by shifting the level of one of both input signals applied simultaneously to the inputs of two logical circuits by means of a constant voltage element. CONSTITUTION:A level shift circuit consisting of a resistance R1, a diode D1 serving as a constant voltage element and a transistor TR Q1 is provided at the input side of two logical circuits L1 and L2 respectively. This level shift circuit shifts the signal Vin supplied to the circuit L1 to a higher level than the signal Vin supplied to the circuit L2 by an amount equal to the forward voltage Vf of the diode D1. Therefore a difference equal to the voltage Vf is produced between the apparent input threshold value Vth1 of the circuit L1 and the Vth2 of the circuit L2. Thus the sufficiently large hysteresis width is obtained and furthermore this hysteresis width is stabilized to be free from the effect of the variation of the power supply voltage.
|
