CD4047B multivibrator cap question

Discussion in 'General Electronics Chat' started by cmartinez, Mar 22, 2015.

  1. cmartinez

    Thread Starter AAC Fanatic!

    Jan 17, 2007
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    Does anyone know if there is a restriction as to the type of capacitor that can be used to determine the frequency of the CD4047B chip? Specifically, can a polarized-type capacitor (like electrolytic or tantalum) be used? And if so, where would its + pin be connected to? See attached datasheet.
    According to the datasheet, the cap goes between pins 1 and 3, but although it does show a normal capacitor symbol it doesn't formally state polarity. So my first guess is that the positive pin goes to to pin 3, and the negative one to pin 1. OR... the chip is restricted to non-polarized ceramic capacitors. Can anyone here clear this out for me? Thanks
     
  2. crutschow

    Expert

    Mar 14, 2008
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    You just didn't read far enough. ;)
    In Section V., Timing Component Limitations, on the bottom-left of page 7, it states the capacitor should be non-polarized. So, if you want to use an electrolytic to obtain a long time-period, you need to use two back-to-back capacitors.
    (Note that tantalum capacitors are electrolytic as well as the more common aluminum electrolytics)
     
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  3. cmartinez

    Thread Starter AAC Fanatic!

    Jan 17, 2007
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    Thanks crutschow... yes... I didn't read far enough... it's just too late and I'm too tired... gotta hit the sac. Down here it's 3 AM
    Thanks again!
     
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