Passing the source current to the output.

[rahdirs]

Hi all,

I have a constant current source whose voltage keeps on varying with time.I used some op-amps in my circuit to perform some operations on voltage & in the mean-process op-amp doesn't allow current to flow with its high-input impedance.How do i make this current appear at the output???

Source - 3.3 V - 15 V,7 A.
I'm thinking of making current at the base of 1st transistor equal to Source Current.

 

[crutschow]

Don't understand your circuit or the problem. What constant current are you referring to?

Can you explain it more completely?

 

[rahdirs]

Providing a path for current at the source to appear at the output

@crutschow:

• Okay,let me re-phrase my question.The source V1 that you see in the schematic is a varying voltage source,it's voltage varies randomly from 3.3 V to 18 V (slowly,no issue of frequency).
• In the circuit, using the two op-amps & 18 V voltage source i brought the voltage to an almost constant 16-17 V.But the op-amps give small current(25 mA),so i used a power-amplifier to increase current.
• But what i'm talking about in previous post is that the source V1 is not only a varying voltage source,but it also gives current in-between 4-7 A.I want to bring this current, to the base of the power-amp,so that i can use this current & decrease the current i draw from Vcc.

• What i want to do finally,is to bring voltage at the o/p of the 2nd op-amp to 16-17 V which i did & also the current to 4-7 A.
• I mean,like the way you do in a trans-impedance amplifier(not talking about current to voltage conversion) pass the current through the feedback paths with probe 1&probe 2 through probe 3 to output,can i make current to flow this way ???

Am I making myself clear?????

I mean now if the current were to pass through the paths with probe 1 & probe 2,then because of low-output impedance of op-amp the current flows into the output of the op-amp,rather than going forward.So i'm thinking of increasing op-amp output impedance so that current from the feedback path doesn't flow into it.Is this correct??