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NOW, the output of Circuit A is current signal, how to implement Circuit B so that Circuit C gets what it want current signal from Cuircuit A. Note, we hope that Circuit B is controlable from outside chip.
What function of circuit B do u expect?
It's a switch (turn-on, turn-off), amplifier with controlable gain. What range of node voltage for link between A and B. U'll need specify this voltage controlable (current conveyor function) or link one with some supply.
Is It PCB circuit or citcuit for on-chip implementation?
“freely” just means, for example, if Circuit C needs 300nA current, you can get 300nA current signal from Circuit A through controlling Circuit B; if Circuit C needs 301nA ,you can also do it through controlling Criuit B； and so on. That is to say, controlled continously。(Note: the current signal from Circuit A is larger than the current into Circuit A.)
(2)this circuit is implemented on chip.
(3) the voltage relation between A and C is not important.
This description looks doubtful. How can i decide what current circuit C is needed? And how can i make control through B, add some fix current value or it's a part of feedback?
It'll better if u show relations by formulas.
looks like a current mirror is what you are looking for, and by control the configuration of current mirror, you can get whatever current you want from B to C, but I am not quite clear about the detailed requirements.
Excuse me, I hurried. The previous schematic is incorrect.
But now, your problem becomes more clear.
If current flow direction is appropriate for you, as mentioned before you can use diff.pair to switch/divide current IA and deliver part of one to sink as IC.
If the N mosfets turned on the left and M mosfets turned on the right that IC=(M/N)*IA, a=M/N.
For a=0.1, 0.2, 0.3, and so on u need 10 pair of mosfets (10 mosfets on each side).
Using biasing voltage for turnon switching allows u utilize more simple schematic of current sinker (IC).
It's requred about 10 posts to understand what u want. And up to now it isn't clear how u suggest to control "a".
U should master to pose a problem more clearly from begining.
As i take ur explanation u need this function: Ic = Ia * A.
A changes continuously in dependence of controlling voltage Vb or current Ib. U don't explain what is controlling amount.
So we can reformulate this for linear dependence: Ic = Ia * K * Vb or Ic = Ia * K * Ib, K - factor. I don't know what dependence u need.
As u can see the result function is curent with current or current with voltage multiplication.
I think u work with large signal. So for voltage processing this kind of circuits is named variable gain amplifier (VGA). But i haven't known VGA equvalent for current processing. I need a time to think about.
What's the transfer function for from Current A to Current C with external controlling? What's the external controlling? It can be adjustable resistor or a voltage? Do you need linear controlling or nonlinear controlling? You need to make clear of your requirement.