# Linear regulator heats up at 60 volts

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
]

• This just begs for a DC to DC switcher. Any reason why not? If not, that's fine. But provide some good reasoning about it.
– jonk
Feb 11, 2020 at 16:18
• Exactly what kind of transistors are you using, in what package? What kind of heatsinks? Feb 11, 2020 at 16:27
• Feb 11, 2020 at 16:34
• @user242388 Yes. Your situation just begs for an IC for that purpose. It's a lot of fun doing it discretely, without an IC. But an IC will be lots easier and lots better in the end. And probably not a lot more expensive. I prefer discrete because I'm anachronistic that way and I enjoy tweaking. I'm a hobbyist. But an IC is probably your better bet if you aren't like me.
– jonk
Feb 11, 2020 at 16:43
• @user242388 Besides, ICs have better, more robust protection schemes that are hard to add with discrete parts.
– jonk
Feb 11, 2020 at 16:49