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Design >> Analog Design >> Constant current source with OTA
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Message started by mikeharvey on Nov 30^th, 2003, 5:59pm

Title: Constant current source with OTA
Post by mikeharvey on Nov 30^th, 2003, 5:59pm

Hello,

I am trying to design a constant current source for a bioelectrical impedance measurement system (final class project). I need 800 microAmps (RMS maximum) at 50 kHz, and I am working with supply voltages of +/- 5 Volts.

A friend suggested using an operational transconductance amp (OTA) such as the CA3080 or NE5517 to construct a VCCS. The datasheets for these parts don't show how to construct a simple constant current source.

Any ideas for the current source (with or without OTAs) would be a great help.

Thanks,
Mike
???

Title: Re: Constant current source with OTA
Post by okguy on Feb 8^th, 2004, 7:48am

In IC there is no way to design a built-in current source. :-[
You need to use an accurate bandgap-based design and an external accurate resistor (1% or less).

OkGuy?