+5N。 Ra 4 8 RESET VCC THRES 3 Vo 555 OUT 8 2TRIG GND 1 Rb Fig.4 Schmitt Trigger (1)Connect circuit as Fig.4 R =100k,R =100k,C=0.1uF (2)Input sinusoidal signal,IkHz,peak to peak voltage is about V2V-31(3) measure the output signal by cursor function. Input signal:peao Output signal:V= Vlan4 8 3 1 2 6 555 Ra Rb +5V C Vo Vi RESET OUT VCC THRES TRIG GND Fig. 4 Schmitt Trigger (1) Connect circuit as Fig.4 100 , 100 , 0.1 Ra b     kR kC F (2) Input sinusoidal signal, 1kHz, peak to peak voltage is about 2 3 V VV peak to peak     (3) measure the output signal by cursor function. Input signal: Vpeak to peak    Vrms  Output signal: Vhigh  Vlow 