Understanding emitter coupled Abstable multivibrator

Discussion in 'General Electronics Chat' started by mguptamel, May 23, 2013.

  1. mguptamel

    Thread Starter Member

    Dec 14, 2012
    37
    0
    Hi all electronic geniuses,

    I was looking at circuit presented in link below.
    http://www.hobby-circuits.com/circu...lasher/808/dark-activated-led-or-lamp-flasher

    Above circuit uses "Emitter coupled astable multi-vibrator". However, I haven't found enough resources which explains inner working of above circuit. There are enough resources for Collector coupled astable multi-vibrator.

    Would anyone be able to help me in understanding this circuit.

    Thanks in advance
     
  2. crutschow

    Expert

    Mar 14, 2008
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    3,244
    A Google search turned up this reference that may help (starts at page 282, para. 7.5).
     
    mguptamel likes this.
  3. mguptamel

    Thread Starter Member

    Dec 14, 2012
    37
    0
    Ahh!!! The whole calculation is very complex. Scrapping my head!!!
     
  4. crutschow

    Expert

    Mar 14, 2008
    13,050
    3,244
    No pain, no gain. ;) Often simple looking circuits can be quite complex in their operation. If you have any specific questions about it, we'll do our best to answer.
     
  5. mguptamel

    Thread Starter Member

    Dec 14, 2012
    37
    0
    Trying to understand how Q2 (right most) turns-on and off? Text is saying Q1 runs in Cut-off & Saturation whereas Q2 runs in Active & cut-off respectively. Got the concept but haven't understood who to work out register values.
     
  6. crutschow

    Expert

    Mar 14, 2008
    13,050
    3,244
    Below is a simulation showing some of the waveforms of interest.

    If you want to do the LTspice simulation yourself (free program from Linear Technology) I can post the .asc file. That's a good way to help learn how a circuit works.

    Mulivibrator.gif
     
    Last edited: May 24, 2013
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