Adding a LED to switch ON when Vin is within window

Discussion in 'General Electronics Chat' started by atferrari, Sep 8, 2015.

  1. atferrari

    Thread Starter AAC Fanatic!

    Jan 6, 2004
    I am about to test a circuit including this integrator and decided to add a LED turning on when Vin is within window.

    Wincomp driving JFET and LED.png

    The actual Vwin (comparator's output) is quite close to what LTSpice predicts.

    Vwin output.png

    Remaining space in the crowded board, allows just a TO92 and few resistors. All what I tried with BJTs created problems to the integrator or did not work.

    Could anyone come with an effective design? I spent one full journey trying in LTSpice because I do not dare to rsik the only two pairs of JFETs I got (2 x 2N5461 Pchannel + 2 x J310 N channel).

    Please note: I need to add a LED and NOT to modify the integrator.

    Just in case I am adding the .asc file plus model and subckt

    Gracias for any ideas.
  2. crutschow


    Mar 14, 2008
    It's not clear to me exactly what you are trying to do and why (how) it doesn't work. :confused:
    Can you post a complete circuit including the LED and BJT.

    What's with the strange blue schematic background color?
  3. atferrari

    Thread Starter AAC Fanatic!

    Jan 6, 2004
    Sorry Carl. Too many things I tried and no one worked.

    The LED has to go ON when Vin is within UL and LL limits.
  4. ericgibbs

    Senior Member

    Jan 29, 2010
    hola at,
    Try this option.
  5. pwdixon


    Oct 11, 2012
    You might want a resistor to ground on the gate of the FET.