Question

If a schmitt trigger has maximum output voltage $\pm 12V,$ Hysteresis loop voltage $V_H$ should be 0.5, reference voltage $V_R=3V,then{V}_{\text{UTP}}$ is

• A. 3 V
• B. 12 V
• C. 0.0625 V
• D. 3.1875 V

Answer 1

The correct option is D 3.1875 V

$V_H=V_{\text{UTP}}-V_{\text{LTP}}$
when $V_0+V_{\text{sat}}$
$V_{\text{UTP}}=V_{ref}\times \frac{R_2}{R_1+R_2}+V_{sat}\times \frac{R_1}{R_1+R_2}$
$-V_{ref}+\frac{R_1}{R_1+R_2}(V_{sat}-V_{ref})$

when, $V_0=-V_{sat}$
$V_{\text{LTP}}=V_{ref}-\frac{R_1}{R_1+R_2}(V_{sat}+V_{ref})$
$V_H=\frac{2R_1}{R_1+R_2}{V}_{sat}$
$0.5=\frac{2R_1}{R_1+R_2}\left(12\right)$
$R_2=47R_1$

$V_{\text{UTP}}=3+\frac{R_1}{R_1+R_2}(12-3)$
$=3+\frac{9}{48}=3.1875V$