Will this current sink work?

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UroBoros

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fast current sink

I need a variable load which can sink 0 to 500mA at 60volts. Need to vary current sink using a potentiometer.

Please see weather this circuit will work as simulated. As I am new to simulation I have some doubts regarding the way I configured the power rails in Proteus. So I doubt about the result of simulation.

Thanks
 

To make it working, V(+) ==V(-) [opamp inputs] ..
For max current 0.5a the voltage across R3 ≈ 2.5V, so the voltage divider R4/RV1 has to produce similar voltage, that is max. 2.5V ..
Also, Q1 has to have a decent heatsink (60V * 0.5A) ..

Rgds,
IanP
 

    UroBoros

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Thanks a lot. meeting after a long gap

But R3 is only 0.5 Ohms(Not 5 Ohms). So 0.3Volts only on pin no 3 of Opamp.


Is it Ok then?

Thanks
 

No. The circuit can only work with an OP, that has a common mode range including negative supply. This isn't the case with TL081. Additionally, as the OP is driving a large capacitive load, it may require a small compensation cap from output to negative input in some cases (particularly a fast OP).
 

    UroBoros

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I suggested using a different OP, but dual supply can work as well. A compensation cap should be used if oscillations occur.
 

    UroBoros

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FvM said:
I suggested using a different OP, but dual supply can work as well. A compensation cap should be used if oscillations occur.
Click to expand...

I have changed the OP to OP07 and introduced dual supply.
Can you suggest a common OP which can be used for this purpose with single supply?

Thanks
 

Picstudent said:
Can you suggest a common OP which can be used for this purpose with single supply?
Thanks
Click to expand...
TLC2272 / TLC272 / LM358 / LM324 can be used.
 

    UroBoros

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