# Voltage Controlled Constant Current Source

My project is to make a Voltage-Controlled Constant Current Source. I have found two solutions… This is first one

http://electronicdesign.com/Articles/Index.cfm?AD=1&ArticleID=9018 [Broken]

Problem is last sentence: For the circuit shown, a maximum current of 20 mA is feasible for a maximum load of 1100 Ω. using higher-voltage op amps and larger power transistors can increase these values if cost isn't a concern.
Cost is not much of a problem, but obtaining those components is hard in Croatia. So that solution is out of the game!!!

Second solution is this one and I will try to make it work

http://www.priorartdatabase.com/IPCOM/000007013/

I am new in electronics and I need help with choosing components for this circuit. This is my basic problem

Specifications are: Ic is constant and max 100 mA, that current is controlled by U1 and U2. The load is variable from 0.5k to 2 kΩ. Second amp will provide constant current because it is connected like Current Source with Floating Load and first amp will provide control voltage.

Circuit works as it should in multisim file is hire

http://adria.fesb.hr/~dgabelic/VCCS.ms9 [Broken]

and the picture is in the attachment...

All help is more then welcome...

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## Answers and Replies

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berkeman
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My project is to make a Voltage-Controlled Constant Current Source. I have found two solutions… This is first one

http://electronicdesign.com/Articles/Index.cfm?AD=1&ArticleID=9018 [Broken]

Problem is last sentence: For the circuit shown, a maximum current of 20 mA is feasible for a maximum load of 1100 Ω. using higher-voltage op amps and larger power transistors can increase these values if cost isn't a concern.
Cost is not much of a problem, but obtaining those components is hard in Croatia. So that solution is out of the game!!!

Second solution is this one and I will try to make it work

http://www.priorartdatabase.com/IPCOM/000007013/

I am new in electronics and I need help with choosing components for this circuit. This is my basic problem

Specifications are: Ic is constant and max 100 mA, that current is controlled by U1 and U2. The load is variable from 0.5k to 2 kΩ. Second amp will provide constant current because it is connected like Current Source with Floating Load and first amp will provide control voltage.

Circuit works as it should in multisim file is hire

http://adria.fesb.hr/~dgabelic/VCCS.ms9 [Broken]

and the picture is in the attachment...

All help is more then welcome...
Welcome to the PF. Coursework questions normally go in the Homework Help forums are of the PF, but for some projects, they can stay here in EE. I haven't decided yet whether to move this thread, but either way, you need to do the bulk of the work on it.

What is your main question exactly? If the simulation works, can't you just use the parts in the simulation, or is that whay you are saying that it is hard for you to get parts? What kind of opamps and transistors can you get?

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