uA741运放组成的施密特触发器电路图
A Schmitt trigger circuit shows two distinct signal input levels for turning the circuit ON and OFF.The difference between the Von and Voff voltages called hysteris Schmitt triggers are useful in conbverting slowly rising waveforms into fast rising ones and in relay like application.
The circuit shown here uses a 741 with positive feedback via R5,R6 and R7 for fast switching.Voltage dividers R8 and r9 set the DC input voltage to the non-inverting input terminal to half the supply voltage.The amount of positive feedback depends on the ratio of R6 and r7.the larger the ratio,the smaller will be the hysterisis shown by the circuit.Potentiometer r2 sets the DC voltage to the inverting input terminal and thus sets the threshold voltage at which the signal will trigger the circuit.The input signal can be applied to either of the two input terminals.