MY goal is to design a regulator which could receive (12 V to 60 volts DC as an input) and 5 volt with 60 to 70 mA current as an output. The reason I used three BJT's NPN (Q1, Q2, Q3), so I thought I could get decrease the heat dissipation by dividing the current through 3 different BJTs (60 mA/3)= 20 mA. Power dissipation= (Vin At the collector -Emitter)*current= (50.30_5.33)*20/1000= 0.9 W and I test them on bread board and it gets very hot, and it makes sense because 1 watts will almost = to 50 degree Celcius, plus the ambient temperature which makes it 75 degree Celsius.
Any expert there in designing voltage regulator, with a smart solution, or what would you recommend? If I Increase the RX value to 800 ohm, the collector voltage will decrease from 50.5 to 5.33 volts and that is perfect, but the problem is when I change the voltage back to 12 volt, then I won't get 5 volt as an output. If I miss any information to add please let me know, and I will get back to you as soon as possible.
[ --- Operating Point --- V(n004): 11.0833 voltage V(a): 6.19012 voltage V(n002): 50.4175 voltage V(n003): 6.18692 voltage V(ve): 05.3231 voltage V(n005): 5.16179 voltage V(n001): 60 voltage V(n006): 5.3231 voltage Ic(Q2): 0.0319418 device_current Ib(Q2): 0.000319418 device_current Ie(Q2): -0.0322612 device_current Ic(Q1): 0.0319418 device_current Ib(Q1): 0.000319418 device_current Ie(Q1): -0.0322612 device_current I(C1): 6.19012e-018 device_current I(D2): -0.242137 device_current I(D1): -0.00180777 device_current I(R6): -0.000638836 device_current I(R5): -0.0645224 device_current I(R3): -0.0322612 device_current I(Rx): -0.0638836 device_current I(R1): -0.244583 device_current I(R4): -0.0322612 device_current I(R2): 0.0024466 device_current I(V2): -0.308467 device_current ]