- #1
anigeo
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Why is the potential difference across a conducting diode zero?
Potential difference across a diode
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Discussion Overview
The discussion revolves around the potential difference across a conducting diode, exploring its implications in electronic circuits, particularly in logic gates. Participants examine the conditions under which a diode may be considered to have zero potential difference and the context in which this assumption is made.
Discussion Character
- Debate/contested
- Technical explanation
- Conceptual clarification
Main Points Raised
- One participant questions why the potential difference across a conducting diode is considered zero.
- Another participant argues that if the potential difference is zero, the diode is not conducting, suggesting that there is always a nonzero voltage unless the current is zero.
- A participant references a book that assumes no potential difference across a diode in the context of signal circuits for OR and AND gates, and cites a video from an EEC professor supporting this view.
- It is proposed that the potential difference across a conducting diode is small and approximately constant over a range of forward currents, often treated as zero for convenience in circuit analysis.
- One participant emphasizes that in practical engineering, insignificant quantities can be regarded as zero, especially in digital circuitry where voltage levels are treated as binary states.
- Another participant notes that understanding the diode curve is essential for the original poster, suggesting that the context of the discussion is important.
- There is a concern that the original poster may be misinterpreting the context of the zero voltage drop statement made in the referenced lecture.
Areas of Agreement / Disagreement
Participants express differing views on the interpretation of potential difference across a diode, with some supporting the idea of treating it as zero in certain contexts, while others challenge this assumption and emphasize the importance of context in understanding the statement.
Contextual Notes
Participants highlight the importance of context in discussions about potential difference, particularly in relation to digital logic circuits and the assumptions made in educational materials.
- #2
dlgoff
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If the potential difference across a diode in zero, it's not conducting.
Looks like there's a nonzero voltage everywhere except when the current is zero.
Unless of course it's shorted internally. But even then, you'll see a potential difference, albeit kinda small.
Looks like there's a nonzero voltage everywhere except when the current is zero.
Unless of course it's shorted internally. But even then, you'll see a potential difference, albeit kinda small.
- #3
anigeo
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but then in explaining the working of the signal circuits of the OR and AND gates , i found the book assuming that there can be no potential difference across a diode
Pls refer to this youtube video from one of the best EEC professors in india(He says the same)
I shall wait for your reply.
Thank you.
Pls refer to this youtube video from one of the best EEC professors in india(He says the same)
I shall wait for your reply.
Thank you.
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- #4
NascentOxygen
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The PD is small and approximately constant over a range of forward currents. In comparison with other voltages around the circuit, it is often convenient to think of it as 0 volts. (We may approximate 0.6V to 0 volts, especially when discussing applications where the difference does not matter. Alternatively, you can picture the discussion as involving idealized diodes.)anigeo said:
It is usually convenient to think of a mechanical switch as having zero volts across it when it is in the ON position, though we all recognize that no practical switch can have 0.000000V across its contacts while conducting useful lighting current in the home.
- #5
sophiecentaur
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anigeo said:
This is the world of Real Engineering, in which insignificant quantities can be validly regarded as zero. If the circuitry that follows a diode is not 'aware' that it isn't zero (when it is near zero) then it IS zero. In digital circuitry, we use 0 and 1 quite happily when neither of those voltage levels is actually 0 or 1.
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- #6
dlgoff
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sophiecentaur said:
I'm thinking that since this is a "Lecture Series on Electronics For Analog Signal Processing", the OP will need to understand the diode curve sooner or later.
- #7
sophiecentaur
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dlgoff said:I'm thinking that since this is a "Lecture Series on Electronics For Analog Signal Processing", the OP will need to understand the diode curve sooner or later.
Oh yes, I agree but the link he gives in which the zero voltage drop statement is made is a lecture on diodes being used in logic circuits. He is taking what the teacher said, out of context.
- #8
dlgoff
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Yea. I wish he/she would have given a link to the lecture on his/her first post. Just trying to justify my response to it.sophiecentaur said:
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