# current to voltage convertor

Discussion in 'The Projects Forum' started by dileepchacko, Dec 18, 2008.

1. ### dileepchacko Thread Starter Active Member

May 13, 2008
102
1
Dear All

I want a current to voltage converter, which is capable of converting 700mA current to voltage. From the simulation result in PSPICE, most of the op-amps (LM324, OP07 etc...) only capable of converting between 1mA to 40mA.Once the input current crosses more than 40mA, output is clipped. Which op-amp can handle this much current.

• ###### C-V convertor.pdf
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Apr 5, 2008
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2,385
Hello,

Take a look at the attached spreadsheet with opamps from National.
Remove the .txt at the end.

Greetings,
Bertus

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3. ### nanovate Distinguished Member

May 7, 2007
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• ###### Current2Volts.jpg
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Last edited: Dec 18, 2008
4. ### Wendy Moderator

Mar 24, 2008
20,772
2,540
Does it matter if there is a shunt resistor involved? Say .1Ω?

5. ### dileepchacko Thread Starter Active Member

May 13, 2008
102
1
no shunt resistor cannot be connected, because a high impudence is required on the input of op-amp

Last edited: Dec 18, 2008
6. ### DickCappels Moderator

Aug 21, 2008
2,756
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Opamps are perfectly happy looking into low impedance sources.

The typical way or converting large currents to voltages is to use a shunt resistor, such as the one in Bill Marsden's circuit. The cool feature of Mr. Marsden's circuit is that it changes a voltage referenced to the postive supply to one that is referenced to ground. Maybe all you need is a small resistance, such as 0.1 ohms to ground (to give 70 mv out when you have 700 ma).

If you need to keep the voltage drop to zero, then you are back to finding a high current output opamp, in which case Burtus's spreadsheet should help.

Does that cover it?

7. ### nanovate Distinguished Member

May 7, 2007
665
1
Then look at hall-effect sensors or other non-contact current sensors. Your circuit example has a very low input impedance -- 50-ohms.

Which circuit is this?