Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

How to design a diode circuit?

  1. Dec 2, 2011 #1
    1. The problem statement, all variables and given/known data
    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).

    2. Relevant equations

    3. 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...
    Last edited: Dec 2, 2011
  2. jcsd
  3. Dec 2, 2011 #2


    User Avatar
    Homework Helper

    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: Dec 2, 2011
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook