Designing voltage regulator using darlington pair of transistor without using zener

[rahul.6sept]

i wanna design a voltage regulator using darlington pair of transistor without using zener.i wanna use a pot so that i can switch between 5 volts and 12 volts.Imax for me is 5amp.Shall i use 2N3055 for both T1 and T2?Also stability factor for me is 0.001%.

Pliz help.

 

[Kral]

Re: Darlington pair

rahul.6sept,
Can you provide more detail? What do you plan on using as a reference? The "input" transistor of a darlington pair only has to supply the base current of the "output" transistor. Therefore, the input transistor can have a much lower power rating, although its voltage rating must be the same as the output transistor. Using a 3055 for the input transistor would work, but it would be overkill.
Regards,
Kral

 

[Siniša]

Re: Darlington pair

I think driving and main transistor should be the least of your worries. 0.001% or 10ppm stability would include temperature and long term stability and line and load regulation I presume. You need to tell us about load and do you need to adjust voltage beween 5-12V or just switch between two?
What is exactly you are trying to do? There may be easier way to solve problem other than building 10ppm 5A PSU...

 

[farzam]

Darlington pair

i think you must use a lower transistor for T1 and 2n3055 for T2. because T1 must drive t2 .that is mean the emiter current of T1 is the base current of T2