Voltage-to-Current Converter

Discussion in 'General Electronics Chat' started by Engr, Apr 21, 2010.

  1. Engr

    Thread Starter Member

    Mar 17, 2010
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    Hi Guys,

    I am looking for a voltage-to-current converter circuit. Can someone give me an idea on how to do this?
     
  2. SgtWookie

    Expert

    Jul 17, 2007
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  3. Engr

    Thread Starter Member

    Mar 17, 2010
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    Most Voltage-to-Current converter circuit that I see uses a Op-Amp. I am just wondering, is there no other circuit that doesn't use an Op-Amp?
     
  4. Wendy

    Moderator

    Mar 24, 2008
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    A simple emitter follower? Voltage in the base of the BJT translates into current down the collector.
     
  5. SgtWookie

    Expert

    Jul 17, 2007
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    Sure, there are other circuits that don't use opamps.

    But why would you want to work that hard?

    Opamps make such circuits very simple, and many opamps are very inexpensive; not much more than you would pay for a few transistors.
     
  6. Engr

    Thread Starter Member

    Mar 17, 2010
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    I want to apply this to a Mosfet. As of now, we are using an Op-Amp for this circuit. See attached file for the circuit configuration. The output of the Op-Amp is the one controlling the gate voltage. With that configuration, we are being limited by the Op-Amp's output when we want a current greater than 80A to pass through the Mosfet since we need a large Vgs to let the 80A pass through the Mosfet. The Op-Amps output is reaching its maximum output which is equal to its supply but the current passing through the Mosfet is not reaching 80A. Maybe using an Op-Amp with a high supply voltage will work but we can't find a Op-Amp with a high supply.
     
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  7. rjenkins

    AAC Fanatic!

    Nov 6, 2005
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    A lot of opamps are rated for 18-0-18V maximum supplies or typically 15-0-15 working voltage.

    You can use one of these on 30V or more single rail, which is way over that needed for fet gate drive.
     
  8. retched

    AAC Fanatic!

    Dec 5, 2009
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    I just snotted. Sarge, that almost cost me a new keyboard and monitor. Hot tea through the nose is not pleasant. That is the greatest thing I have ever seen.
     
  9. hgmjr

    Moderator

    Jan 28, 2005
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    Another way to convert a voltage to a current is a BJT current mirror.

    hgmjr
     
  10. SgtWookie

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  11. Engr

    Thread Starter Member

    Mar 17, 2010
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    I review the datasheet of MSK 130 and I think it can work. I will try it first...
     
  12. Ron H

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    Apr 14, 2005
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  13. SgtWookie

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    Jul 17, 2007
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    Peanuts!*;)
     
  14. Engr

    Thread Starter Member

    Mar 17, 2010
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    I know the power dissipation will be high but if this will make my circuit work then I have to go for it unless otherwise I have an alternative which will give me the same result.
     
  15. SgtWookie

    Expert

    Jul 17, 2007
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    I have a feeling that your MOSFET will vaporize in a bright flash of light. :eek:
     
  16. Engr

    Thread Starter Member

    Mar 17, 2010
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    It has a possibility that it can happen but we have to meet that requirement since that is the requirement of the device where our design is to be applied. If the device is going to be damaged or destroyed then we have to get back to the designer of the device and tell him that the specs that they are giving is too much for their device...
     
  17. blueroomelectronics

    AAC Fanatic!

    Jul 22, 2007
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    What is this device used for?
     
  18. Engr

    Thread Starter Member

    Mar 17, 2010
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    this circuit will be applied to test mosfet devices...
     
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