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Current sources

Hello, Please look at the following data sheet of an instrumentation amplifier

INA2133.

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I am using it as a constant current source ( figure 16, page 13 ). I made the following changes in the circuit

  1. I put a capcitor in series with the load for AC coupling reason.
  2. The power supply of the circuit is +/- 15 volts.

I have a following questions about the circuit.

  1. For example, if the circuit is producing 100microA and the load resistance is 1mega ohm then the complaince voltage will be +/- 10 volts or the voltage across the load will be +/- 10 volts. How can I keep the complaince voltage or voltage across the load equal to +/-
0.7 volts with the current of 100microA without changing the power supply which is +/-15 volts?

Please advice! Thanks John

Reply to
john
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Hi,

I am using a iridium oxide material as a load. when voltage exceeds the

+/- o.7voltage limit, the material breaks down. I need to protect the material.

Thanks John

Rich Grise wrote:

Reply to
john

Hi.

+/- 0.5 will be ok too! please advice

Thanks John

Reply to
john

On Fri, 13 Jan 2006 08:31:17 -0800, john wrote: ...

Well, what load resistance would develop 0.7V with 100 uA through it?

What's the reactance of the cap at the frequency in question?

Good Luck! Rich

Reply to
Rich Grise

How close to 0.7V do you have to go? Would (say) 0.5V compliance be enough, or do you need 0.699V?

Best regards, Spehro Pefhany

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Reply to
Spehro Pefhany

What, exactly, is the specification of the load? Are you sure that what you want to use on it is a "current source", when the load is so touchy about voltage?

What is it you're trying to accomplish? Please give an overall overview, like, "I'm trying to do so-and-so with such-and-such a thing, and the thing looks like this..." that sort of thing. (redundancy unintended, apologies to the pedant contingent ;-).)

Thanks! Rich

Reply to
Rich Grise

If 0.6V (about) would do, then a couple of standard diodes across it will work. For 0.7V, two shocketty(sp?) diodes in series may work. If the sole aim is protecting the device.

Reply to
Ian Stirling

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