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npn to pnp signal

Discussion in 'The Projects Forum' started by farooque, Sep 22, 2012.

  1. farooque

    Thread Starter New Member

    Sep 22, 2012
    i want to convert npn sensor output signal into pnp signal.
    pls help me to make a circuit for this converter.
  2. MikeML

    AAC Fanatic!

    Oct 2, 2009
    This is not standard terminology. Could you attach a diagram of your existing sensor output?
  3. crutschow


    Mar 14, 2008
    Your question is incomplete. It's always possible for a signal to go from an NPN transistor to a PNP transistor as long as the bias levels are correct. What are you trying to accomplish?
  4. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
    Do you want to invert the signal,

    IE. when your sensor detects it goes low instead of high and vice-versa?
    if so put an inverter on the output, or another npn transistor.
  5. Ron H

    AAC Fanatic!

    Apr 14, 2005
    What is your supply voltage? How much current must the PNP source?
  6. Jony130

    AAC Fanatic!

    Feb 17, 2009
    Well this is a standard terminology when you work in maintenance as a control engineering.
    Simply use a relay as a inverter.

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  7. Dyslexicbloke

    Distinguished Member

    Sep 4, 2010
    I think farooque is probably talking about an open collector output, that would be pretty standard.

    F) Generally speaking you would hook the sensor to a high impedance input that is pulled up with a resistor but you need to appreciate that your function is inverted IE active low.

    The simplest, external inverting circuit I can think of would be to use a line driver chip, ULN200##. they are good for reasonable voltages and support a fairly hefty current, relatively speaking. they provide the same open collector output as your sensor so if you pull up your input and also pull up the sensor output on the chip you get an active high.

    Using a transistor and a few current resistors to limit current and apply bias could give you an open collector output that is positive.

    If you want an output that can both sink and source, open collector in both states then you need a half bridge driven from your original sensor.