VCCS

[mohammed elzaq]

I want anyone to guide me to design VCCS.

 

[Roff]

You need to provide some specifications:
1. Output current range.
2. Output voltage range.
3. Input control voltage range.
There may be others, such as accuracy, minimum output impedance, output current bandwidth, etc., but these three are absolutely necessary.

 

[mohammed elzaq]

actually , i need to design acurrent source with 1-5 mA and 15 Khz
i designed simple sine wave generator cascaded with voltage to current converter circuit , but the problem is the current at certain value of the load resistor is fixed then start dropping when the load resistor change.
i want to design currnt source with same range ( whatever the value of tje load resistor is) , the current must not be affected by the resistor load.
my idea is control system that when there is drop of the current value , input of the V-to -I converter start to be fed whith more voltage that will keep the current value at its original value.

 

[Roff]

actually , i need to design acurrent source with 1-5 mA and 15 Khz
i designed simple sine wave generator cascaded with voltage to current converter circuit , but the problem is the current at certain value of the load resistor is fixed then start dropping when the load resistor change.
i want to design currnt source with same range ( whatever the value of tje load resistor is) , the current must not be affected by the resistor load.
my idea is control system that when there is drop of the current value , input of the V-to -I converter start to be fed whith more voltage that will keep the current value at its original value.

I'm still not clear what you want. Post a schematic of what you have designed, and explain what it should do, but doesn't. If you can't post a schematic, then post a block diagram of what you want.
We need to know if the current is sourcing or sinking, bipolar or unipolar, and is the load grounded or can it be floating.