555 Output Characteristics

Discussion in 'General Electronics Chat' started by Wendy, May 9, 2010.

  1. Wendy

    Thread Starter Moderator

    Mar 24, 2008
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    SgtWookie and I had a discussion about 555 output and how much they can drive. I've started some circuits to test the concept. The first one kind establishes the basics.

    [​IMG]

    The voltage was exactly 4.500, the output was 2.744VDC. This meant the circuit was drawing around 196ma give or take a bit.

    I think we met the basic specs, though the voltage drop was a bit high.

    I'm going to redesign my current source sink a bit.
     
  2. SgtWookie

    Expert

    Jul 17, 2007
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    Bill,
    Why not use an LM317 as a current sink? 6.25 Ohms from OUT to ADJ (1/2 Watt) should just about get you there; try a 9.1 Ohm and a 20 Ohm resistor in parallel. Then you can determine the voltage drop from the 555 under minimal load and 200mA load conditions.
     
  3. Wendy

    Thread Starter Moderator

    Mar 24, 2008
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    To use a 555 at 4.5VDC means it will below the minimum thresh hold insertion drop for a LM317. The first experiment was quick and dirty, and let me know I wouldn't be wasting my time doing more. I'm going to set it aside for a little bit, then get back to it.

    I also have several different makes of 555s in my kits. The first was a KIA555.

    **********************

    Here is the type of regulators I'm thinking of using...

    [​IMG]
     
    Last edited: May 10, 2010
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