例3由三运放放大器组成的温度测量电路 U=+5V ○O A1+ R R R R A3 RI NRt DO RR A2+ Rt热敏电阻 集成化:仪表放大器 Rt-r Rt=f(T°C) U 2(Rt+R R 2R+R R 2R+Rw Rt-R R R 2(Rt+R)
例3 由三运放放大器组成的温度测量电路 uo R1 R1 + + A3 R2 R2 + + A1 _ + A2 R R RW + U=+5V R R R Rt ui ui = Rt - R 2(Rt+R) U Rt 热敏电阻 (u u ) R 2R R R R i2 i1 W W 1 2 − + u o = ui = (u u ) R 2R R R R i2 i1 W W 1 2 − + Rt - R 2(Rt+R) U Rt=f(T°C) 集成化:仪表放大器
例4求电压放大倍数Aau/u; u=u4=0 F b+ F 0 R b tIR2 RI RE R P R uFup=u。u F 3 F R R 2 3 Rp=r//(rF+r2lr3) RrR RER RE+r R+R2+ F F 2 R A R R
例4 求电压放大倍数Au=uo /ui 。 i i b+ =0 b- =0, u-= u+=0 _ + + RF R1 RP ui uo i1 iF ibib+ R2 R3 i2 i3 uF i1 =iF = i2 +i3 ui R1 -uF RF = = -uF RF uF -uo R2 uF R3 + uo = - R ui 1 RF + R2 + RF R2 R3 R1 RF + R2 + RF R2 A R3 u= – RP=R1 //(RF + R2 //R3 )