Unity Gain current buffer Zin

Discussion in 'Homework Help' started by duffman268, Feb 7, 2013.

  1. duffman268

    Thread Starter New Member

    Feb 7, 2013
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    I have a circuit with a unity gain current buffer in the box. I want to figure out the input impedance and its equivalent circuit, but I'm not sure how I'm supposed to do that. Can anyone help me?
     
  2. The Electrician

    AAC Fanatic!

    Oct 9, 2007
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    Add a 1 amp current source injecting the 1 amp into the Zin node. calculate the voltage at that node due to the current source. That voltage divided by the 1 amp will be the impedance there.
     
  3. BillO

    Well-Known Member

    Nov 24, 2008
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    An amp! If it is a high Z buffer, the voltage might need to be in the mega volts!

    No, don't try to pump an amp into it.

    All you need is a known voltage (V) and a known resistance (R). Connect V to the input of the buffer through R and measure the current (I). Use Ohm's law to get the Z of the input stage of the buffer.

    Z = (V/I) - R

    Of course, that is just the DC part of it. Now you will need to calculate the Z of the LC circuit.

    Edit: BTW, that looks like a pretty good equivalent circuit to me.
     
    Last edited: Feb 9, 2013
  4. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    Do you suppose that would cause sparks and smoke to erupt from the paper and pencil he's working with?:D
     
  5. The Electrician

    AAC Fanatic!

    Oct 9, 2007
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    It would undoubtedly blow out the LCD display of his calculator!
     
    Ron H likes this.
  6. BillO

    Well-Known Member

    Nov 24, 2008
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    LOL, yes, literary sparks might fly!
     
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