Chapter 15, Problem 15.7EP

Redesign the street light control circuit shown in Figure 15.32(a) such that the switching voltage is $V_S=1\text{V}$ and the hysteresis width is 100 mV. Assume $V_H=+10\text{V}$ and $V_L=-10\text{V}$ . Also, findR such that $I=200\mu \text{A}$ when ${\upsilon }_O=V_H$ . Assume ${\upsilon }_{BE}\left(\text{on}\right)=0.7\text{V}$ and $V_{\gamma }=0.7\text{V}$ , and assume the relayswitch resistance is $100\Omega$ . (Ans. $R_2/R_1=199$ , $V_{\text{REF}}=1.005\text{V}$ , $R=42.9\text{k}\Omega$ )