Uncovering the On/Off Ratio of Silicon Transistors

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SUMMARY

The typical on/off ratio of silicon transistors is not a conventional term; instead, the focus should be on the static on-current to off-current ratio, which is extremely high in modern transistors. For silicon transistors, the fully on state occurs at approximately 0.7 volts with a collector-emitter current determined by the transistor's beta. The critical factor for efficiency in logic circuits is the switching speed, characterized by the transistor's slew rate. Understanding these parameters is essential for optimizing transistor performance in electronic applications.

PREREQUISITES
  • Understanding of silicon transistor operation and characteristics
  • Familiarity with DC current gain (beta) in transistors
  • Knowledge of voltage levels in transistor switching (e.g., 0.7 volts for saturation)
  • Concept of slew rate in electronic components
NEXT STEPS
  • Research "transistor slew rate" to understand switching efficiency
  • Explore "DC current gain (beta) in silicon transistors" for performance insights
  • Study "on-current vs off-current ratios in modern transistors" for efficiency analysis
  • Investigate "transistor switching characteristics" to optimize logic circuit design
USEFUL FOR

Electrical engineers, circuit designers, and anyone involved in optimizing silicon transistor performance in logic circuits will benefit from this discussion.

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.
 
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