Constant Current Circuit Diagram using a tip117

[jmills]

hello all,

does anyone have or know where I can get a constant current circuit diagram using a tip117 transistor?

I am new to electronics, forgive me if this question lacks anything...

thanks!!!
Ψ≈Ω∞

 

[crutschow]

Why do you want to use that particular transistor as a current source?

How much current? What voltage? Does it drive a grounded load?

 

[MikeMl]

It lacks a lot:

What current range?

What is the load? LED?

How precisely do you need to control the current?

What voltage are you starting from?

What sets the desired current? Pot? Control voltage?

 

[jmills]

What current range?
20-40 mA

What is the load? LED?
variable...

How precisely do you need to control the current?
3-4% ???

What voltage are you starting from?
32 V

What sets the desired current? Pot? Control voltage?
pot

Does it drive a grounded load?
no

Why do you want to use that particular transistor as a current source?
reverse engineer... maybe a different part could work???

let me know if you guys need more... i will try to get it

thanks...

 

[Mr RB]

I think we might need the range of input voltages. Ie Vin max and Vin min.

 

[moffy]

connect your voltage ref in parallel with the pot. Connect the -ve end of the ref/pot to the anode of a diode(1n914 etc). Connect the cathode of the diode to ground. Bias the pot/ref with a resistor to V+. Connect the wiper to the base of an npn transistor. Connect the emitter to Re (an emitter resitor) connect the other side of Re to ground. The collector of the npn is your current source, the single diode provides some Vbe compensation.

 

[jmills]

Thanks moffy... Mr RB... I will try to get those... thanks..