Uncovering the On/Off Ratio of Silicon Transistors

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Discussion Overview

The discussion revolves around the on/off ratio of silicon transistors, exploring its definition, significance in logic circuits, and implications for efficiency. Participants seek to clarify terminology and understand the practical aspects of transistor operation.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant inquires about the typical on/off ratio of silicon transistors and its required threshold for proper function in logic circuits.
  • Another participant questions the terminology of "on/off ratio," suggesting it is not conventional and explains the conditions for a transistor being fully on or off.
  • A third participant proposes that the inquiry may relate to the duty cycle or the ratio of on-current to off-current, indicating that modern transistors typically have a very high static on/off current ratio, but emphasizes the importance of switching speed instead.
  • A brief response states a simplistic view of the on/off ratio as ranging from 0% to 100%.

Areas of Agreement / Disagreement

Participants express differing interpretations of the term "on/off ratio," leading to a lack of consensus on its definition and relevance. The discussion remains unresolved regarding the specific metrics and implications for transistor performance.

Contextual Notes

There are ambiguities in the terminology used, and the discussion reflects varying assumptions about what constitutes the on/off ratio and its significance in practical applications.

Who May Find This Useful

Individuals interested in semiconductor physics, electrical engineering, and the design of logic circuits may find this discussion relevant.

DanielFaraday
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Research-related question:

What is the typical on/off ratio of a silicon transistor? This seems like basic information, but I can't find it anywhere.

Also, how high does the on/off ration need to be in order for transistors (say, in a logic circuit) to function correctly?

Thanks!
 
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What do you mean by "on/off ratio"? This is not a conventional transistor terminology. A transistor which is fully off has zero volts base bias with respect to the emitter and passes approximately zero current (there is some very slight leakage, but this is ignored in practice). A transistor which is fully on has a saturated gate condition with a bias voltage of (for silicon) about .7 volts and passes a collector-emitter current equal to the base current times beta (the DC current gain of that particular transistor).
 
Do you mean the duty cycle in a typical application? or do you mean the ratio of on-current to off-current for a given transistor? If the latter, it kinda looks like you are interested in efficiency. The static on-current to off-current ratio in modern transistors is typically extremely high and not an issue. The real problem in efficiency is how quickly the transistor can switch on and off. You characterize that with, for example, a time domain plot of current when it switches. Google transistor slew rate, for example.
 
0% to 100%.
 

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