0~5V定電壓150mA限流電路設計

OP製作定電壓線路.
(1)PWM來自MCU, OP+前方兩級低通濾波. if PWM=100%, 3.3V, OP-=3.3V,
     3.3/10K*5K1+3.3V=4.983V,
(2)AD5可量測VO電壓, if AD5=2.491V, =>VO=4.983V.
(3)2SC4081 Io=150mA, if 2SC4672輸出電流太多, 4081 VCE下降,故4672 VBE下降,Io下降.
(4)if GPIO=1, U12 NMOS Vg<Vs, NMOS=>OFF, VO=0V.
    if GPIO=0; U12 NMOS Vg=12V>Vs, NMOS=>ON, VO=5V
(5)R72,R73 3R 1206電阻當fuse, 當Io=300mA, 0.3*0.3*3R> 1206 0.25W, R72&R73燒掉.