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Understand & Apply the Transimpedance Amplifier

Even though we publish new blogs daily from your intrepid editor and from a number of well known writers, sometimes it's good to have a look back at some of our well received articles from the recent past. Here is one that discusses the transimpedance amplifier. What is a transimpedance amplifier? Where might you use one? What are the pitfalls of using one without properly compensating the device?

The article was written by David Westerman, at the time an Applications Engineer for National Semiconductor (now part of TI).

10 comments on “Understand & Apply the Transimpedance Amplifier

  1. goafrit2
    February 28, 2013

    An amp that produces  voltage output with current input.

  2. Brad Albing
    February 28, 2013

    Exactly right. It has a trans fer function that converts in this manner:

    (Output of amplifier)/(Input to amplifier) = (V-out)/(I-in)

    V/I = R (Ohm's law) or more generally, v/i = Z where v and i are the AC components of the signal and are complex – hence the result is impedance not resistance. And that's why it's called a trans impedance amplifier.

  3. amrutah
    February 28, 2013

    Brad, Thanks for sharing the link.  I have never used transimpedance amplifiers in design though on chip I have used many V2I convertors.  Any instances where Transimpedance Amps are used on chip?

    Note: Looks like the link to part 1 is broken.

     

  4. SunitaT
    February 28, 2013

    @Brad, thanks for sharing the link, very informative. Could you please post the link for Part -1 as well because I am not able to access the part-1 from the link mentioned int he article.

  5. Brad Albing
    February 28, 2013

    I'll have that fixed shortly.

  6. Brad Albing
    March 1, 2013

    OK – just a couple of busted links – all fixed now, so read both parts 1 and 2. let me know of any questions you have.

  7. DEREK.KOONCE
    March 5, 2013

    Anyone notice a missing line to the inverting input in figure 5?

    Wonderful and detailed article. Key factor is that the output is adjusting to keep the inputs equal by pushing or pulling current through the feedback.

  8. Brad Albing
    March 5, 2013

    Huh – well, yes – now I do. Hmm… I'll see if I can fix that.

  9. Brad Albing
    March 5, 2013

    Based on what the author says in the paragraph just above Figure 5, I think that omission is intentional.

  10. goafrit2
    April 5, 2013

    >> V/I = R (Ohm's law) or more generally, v/i = Z where v and i are the AC components of the signal and are complex – hence the result isimpedance not resistance. And that's why it's called a transimpedance amplifier.

    It is very possible you could be a good professor. In this two-sentence comment, you simply and clearly explained these terms.

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