Can You Design a Diode Circuit to Turn On at 5V and Off at 15V?

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SUMMARY

The discussion focuses on designing a diode circuit that activates at 5V and deactivates at 15V using standard diodes and resistors. The participant successfully turns the circuit on at 5V by using seven standard 0.7V threshold diodes in series. However, they encounter issues with current behavior, noting that it plateaus after 5V and do not achieve the desired functionality without incorporating a transistor. The conclusion is that a transistor is necessary for proper operation within the specified voltage range.

PREREQUISITES
  • Understanding of diode characteristics, specifically 0.7V threshold voltage.
  • Basic knowledge of circuit design involving resistors and voltage sources.
  • Familiarity with transistor operation and its role in circuit control.
  • Knowledge of voltage divider principles and current behavior in circuits.
NEXT STEPS
  • Research how to integrate transistors into diode circuits for voltage control.
  • Learn about voltage divider circuits and their applications in controlling voltage levels.
  • Study the current-voltage characteristics of diodes to understand their behavior in circuits.
  • Explore practical applications of diode and transistor combinations in electronic design.
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Electronics students, circuit designers, and hobbyists interested in voltage control and diode applications in electronic circuits.

sadf
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Homework Statement


Given an input range of voltages (for example, 5-15V), design a circuit using resistors and diodes (and voltage sources) to turn on at input = 5V and turn off at input = 15V. (I chose 5 and 15 arbitrarily).

Homework Equations


The Attempt at a Solution



I am able to get it to turn on at 5V (I would just put about 7 of the standard 0.7V threshold diodes in series), but my understanding is that the current will skyrocket at 5V and then plateau at a voltage slightly higher than 5. I don't know how to get it to continue rising until 15V and then stop there...
 
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Welcome to PF, sadf!

I thought I had an idea, then realized it was wrong.
I now think it is impossible to do this without a transistor.
 
Last edited:

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