Understanding Op-Amp: Get Help with Physics & Functions

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Discussion Overview

The discussion centers around understanding operational amplifiers (op-amps), their functions, and the underlying physics. Participants explore the differences between op-amps and simple connections, particularly in terms of voltage and power gain.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant expresses confusion about the concept of current being "channeled" and questions the necessity of op-amps compared to a simple wire.
  • Another participant clarifies that the key difference lies in the voltage gain of op-amps, noting that they can provide power gain compared to a direct connection.
  • The explanation includes that while a voltage follower configuration with a wire has a voltage gain of 1, an op-amp can supply more current, thus allowing for power gain, which is crucial for processing weak signals.
  • A humorous remark suggests that op-amps allow for "spying" on signals without being detected, adding a light-hearted element to the discussion.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the initial question regarding the necessity of op-amps versus simple connections, as some express confusion while others attempt to clarify the differences in functionality.

Contextual Notes

Some participants reference external resources, such as Wikipedia and a specific book, suggesting that further reading may provide additional clarity on the topic.

hurliehoo
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Hi can anyone help me get my head round how op-amps work? I know this is a silly question but ...

Their functions (ie what a summing amp does etc) seem fairly clear. However maybe my question has more to do with the physics of what's happening but if the resistance between the two voltage input pins is practically infinite and the current is effectively being channeled, then why not just have a simple line instead of an op-amp component?
 
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I'm afraid I don't understand what you mean by "and the current is effectively being channeled", and by "why not have a simple line instead of an op-amp component".
 
hurliehoo said:
Hi can anyone help me get my head round how op-amps work? I know this is a silly question but ...

Their functions (ie what a summing amp does etc) seem fairly clear. However maybe my question has more to do with the physics of what's happening but if the resistance between the two voltage input pins is practically infinite and the current is effectively being channeled, then why not just have a simple line instead of an op-amp component?

The difference is the voltage gain of the opamp. There is very high voltage gain between the differential input pins and the output, so the output can have power gain compared to the input signal.

So in a voltage follower, for example, if you just have a straight wire, the voltage gain is 1 and the current gain is 1, and there is no power gain. When you use an opamp in the voltage follower configuration, the voltage gain is 1, but the opamp's output amplifier stage can supply more current than the input signal can (generally), so there is power gain.

The power gain is important for being able to process weak signals, and for driving power loads.

Hope that helps. Read over the wikipedia page, and come back with specific questions if you have them. You might also see if your school library has a copy of "The Art of Electronics" by Horowitz and Hill -- the chapter on Feedback and Opamps may be helpful for you.
 
the op-amp allows you to spy on a signal without being seen. ;)
 

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