Design of constant current source.

[Jyothi koneru]

hello everyone,
Iam new to this group,
i need your suggestions regarding designing a constant current source which is capable of generating currents in micro amps,
which ICs are best suits .
Thanks in advance.

 

[Harald Kapp]

Any circuit based on an operational amplifier can be used. The offset voltage and current of the opamp you select should be very low to minimize the influence on the μA current to be regulated.

 

[BobK]

What is the voltage compliance range? I.e. from low to high, how much voltage must it be able to put out. Which is really the same question as what is the range of impedances of the load?

How accurate does it have to be.

If the voltage is reasonably low, like a few volts, 24V supply + a resistor might be all you need.


For example, if you need 5uA into a load that varies from 100K to 500K, the voltage compliance range would be 0.5 to 2.5V. If you used a 24V regulated supply and a 4.5 Meg resistor, you currents would range from 4.8 to 5.2uA. A higher voltage would give better results.

Bob