Hi,

I would like to design a power supply that can source and sink constant current using below configuration.
However when I built my circuit, Q1 and Q2 are dissipating too much power because Vce is too high.
I tried using BJTs with larger packages but they are hurting dynamic switching response because of lower f_t.
Is there any way to decrease Vce so that Q1 and Q2 won't get too hot?
Would stacking two BJTs (2 NPNs and 2 PNPs) solve the problem? If yes, how should I bias them?

Thanks!

 

Hello,

What current level do you want to realize?
With the 10 Ohms resistors in the emittors of the transistors it will be quite limited.
Did you think of using a power opamp?

Bertus

 

Hello,

What current level do you want to realize?
With the 10 Ohms resistors in the emittors of the transistors it will be quite limited.
Did you think of using a power opamp?

Bertus

Hi,

I'm trying to source/sink 100mA. Sorry for the confusion but the component values above are not the exact values I used.
I used above circuit as a reference and below is the one I actually built.
It's a Howland current source with current buffer. With +/-1V input voltage, I'm trying to source or sink 100mA to the load V9.

 

What is the maximum load resistance or load voltage for 100mA of current.
That will determine the minimum supply voltage you can use.

 

Hello,

Your schematic is different from the previous posted schematic.
In the schamatic in post #1 the - input of the opamp is connected to the sense resistor.
In your schematic it is connected to the output.
Also the sense resistor is connected to the + input of the opamp, wich is likely not correct.

Bertus