How to extend the output range of the following circuit?

[anushaas]

Given below is the circuit designed for a pulsed low current test source.

The minimum current generated from this circuit is of the order of some 12nA.(Output waveform is as shown).

I want to know if it is possible to extend the output to some pA range say few tens of pA.
Also what could be an alternative component for LF347 and 2N4416 used in this circuit?

 

[erikl]

I want to know if it is possible to extend the output to some pA range say few tens of pA.

Your pulsed output current is already in the range of some pA (14pA). How much would you like to extend it?

 

[anushaas]

I could not follow you sir.The pulsed output is fluctuating between 12.914006nA and 12.913992nA.

 

[erikl]

The pulsed output is fluctuating between 12.914006nA and 12.913992nA.

True, and I think the difference is 14pA , isn't it?

---------- Post added at 18:10 ---------- Previous post was at 18:09 ----------

The pulsed output is fluctuating between 12.914006nA and 12.913992nA.

True; and the difference is 14pA, isn't it?

 

[anushaas]

True, and I think the difference is 14pA , isn't it?

---------- Post added at 18:10 ---------- Previous post was at 18:09 ----------


True; and the difference is 14pA, isn't it?

The difference between peaks?
Isn't that .014 pA?:???:

 

[erikl]

The difference between peaks? Isn't that .014 pA?:???:

Oh yes, you're right, sorry :sad:, 14fA ! And what do you need, actually? I can't get it from your description above.

 

[anushaas]

Oh yes, you're right, sorry :sad:, 14fA ! And what do you need, actually? I can't get it from your description above.

Sir I want the output to be a few picoAmps.Also is there an alternative for LF347 and 2N4416 because I don't have both these components with me.