current independent on the load

[Dino1400]

Hello,

I have circuit that generate different waveforms with frequencies from 20Hz to 1MHz the current without load is 100uA this current increase as the load circuit changes.

any suggestion on how to have this current independent on the load


Thank you all

 

[barry]

If you have no load, where is your 100uA going?

It sounds like you have a voltage output, and what you want is a current output. So, what you want is a voltage-controlled current source. This might help:
**broken link removed**

 

[Dino1400]

first thank you for your reply,

sorry i miss interpret that 100uA is for high resistance and as we decrease the resistance the current increases.

1) AC current output that so far is depends on the load
2) I like to have the current fix with different load independent of load

 

[barry]

first thank you for your reply,

sorry i miss interpret that 100uA is for high resistance and as we decrease the resistance the current increases.

1) AC current output that so far is depends on the load
2) I like to have the current fix with different load independent of load

Yes, as I explained, I think you want a voltage to current converter. Did you look at the link I posted?

 

[Dino1400]

great info thank you very much

 

[Dino1400]

i have tried the circuit list you provide but i don't have a negative voltage to operate the opamp (-Vs).
any circuit that operate with just positive voltage

 

[Los Frijoles]

Most op-amps require a negative voltage. The problem is that they can't quite output all the way to their +V and -V power rails, so if you want 0V to come out of your op-amp, you need a voltage less than 0 so it can actually reach down that far (strange as that sounds). So, you could hook -Vs to ground, but you would always have some current coming out of your current source and the circuit wouldn't work properly since the output of the op-amp wouldn't be able to do 0V (it would probably get down to 1.4V or something).

What you need is a Single supply op-amp with Rail to rail operation.

The single-supply means it doesn't need a negative supply (usually) and rail-to-rail means it can actually output all the way up to +V or all the way down to -V (in this case 0V up to +V).

I didn't look at the circuit in detail, but I would imagine that the output of the op-amp is always positive and the inputs are generally positive. If you can be sure that you won't have any negative voltages going in to your op-amp and that you won't need any negative voltages coming out, you should be able to just drop in a single-supply op-amp as a replacement.

I found an interesting article here about using single-supply op-amps: https://www.ti.com/lit/an/slyt189/slyt189.pdf

 

[D.A.(Tony)Stewart]

What Vmax, Imax and Zload do you expect? Reactive ?