| 摘要 |
PURPOSE:To increase the hysteresis width, by providing a plurality of transistors(TRs) in series connection driven at the same time through the output of a voltage comparator and a feedback resistor, and to make the set of hysteresis easy by making a rising leading threshold level stable. CONSTITUTION:An input voltage V1 of a voltage comparator A is compared with a reference value dividing a power supply voltage VCC by resistors R1, R2. TRsQ1, Q2 are driven with an output of the comparator A and turned on/ off by a base current control resistor R5 inserted to the Q1 side. When the Q1, Q2 are turned on and an output VO is at L level, a feedback current flows in the path of VCC-R1-R3-N2-Q1-GND and the falling threshold level is set low. Inversely, when the Q1, Q2 are turned off, the output VO is at H level, and since the circuit part between points N1, N2 is turned off, the variance of H level of the VO does not give any effect on the rising threshold level. |
