Is there such a thing as an inverted zener diode?

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Discussion Overview

The discussion revolves around the concept of a hypothetical diode that allows current to flow only when the voltage is below a certain threshold. Participants explore whether such a device exists and consider various alternatives and related components.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants describe Zener diodes as allowing current to flow in reverse when the voltage exceeds a certain level, prompting the question of whether an "inverted" version exists.
  • One participant suggests that a fuse could serve a similar purpose, although notes that fuses operate based on current rather than voltage.
  • Another participant mentions Raychem's Polyswitch as a potential alternative, but also points out its reliance on current.
  • A participant argues that devices allowing current to flow easily would not permit significant voltage buildup, suggesting that a fuse is a close approximation.
  • A linear voltage regulator is proposed as a device that can maintain a maximum output voltage, allowing power to flow as long as the input voltage is below a certain level.
  • One participant asserts that no single semiconductor device exists that meets the criteria of allowing current flow only below a certain voltage, but acknowledges that a circuit could be designed for over-voltage cutout.

Areas of Agreement / Disagreement

Participants express differing views on whether a single semiconductor device can fulfill the proposed function, with some suggesting alternatives while others maintain that such a device does not exist. The discussion remains unresolved regarding the existence of an "inverted" diode.

Contextual Notes

Participants reference various components and their operational principles, highlighting the limitations of each in relation to the original question. There is an emphasis on the conditions under which these devices operate, particularly regarding current versus voltage.

Who May Find This Useful

This discussion may be of interest to electronics enthusiasts, engineers, and students exploring circuit design and component functionality.

warfreak131
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Zener diodes act like regular diodes, except that they allow current to flow in the reverse direction if the voltage is high enough. That is, current with voltage ABOVE a certain value will flow.

My question is, is there such a diode that only allows current to flow if the voltage is BELOW a certain level?
 
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warfreak131 said:
Zener diodes act like regular diodes, except that they allow current to flow in the reverse direction if the voltage is high enough. That is, current with voltage ABOVE a certain value will flow.

My question is, is there such a diode that only allows current to flow if the voltage is BELOW a certain level?

A fuse? (well, fuses are based on current and not voltage...)

Or maybe Raychem's Polyswitch? (same caveat, though...)

http://www.te.com/en/products/circu...nt-devices/polyswitch-resettable-devices.html

.
 
Think about what you are saying. Anything that allows current to easily flow will not likely allow a voltage to build up across it. So Berkemans suggestion of a fuse is pretty close to accurate. You could consider a wirewound resistor also. When they are over heated (too much current) they open up instead of sit and smoke.
 
A linear voltage regulator will hold output to a set maximum voltage, and if the input falls below Vreg, power will continue to flow.

A basic 3-terminal regulator can be used without any additional components, so it's really no harder to use than a Zener diode.
 
warfreak131 said:
My question is, is there such a diode that only allows current to flow if the voltage is BELOW a certain level?
No, not a single semiconductor device. But you can build a circuit to do this, it has over-voltage cutout.
 

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