4013 flip flop, which pins to ground?

• 4013 flip flop, which pins to ground?
  Posted by Chris Wilson on 26 Jul, 2015 00:44
• I have built this circuit, and I am unsure which pins on IC4, a 4013 D type flip flop, should be grounded.
  
  Unused pins are 8, 9, 10, 11, 12 and 13. Should I ground 8, 9, 10 and 11?
  
  I don't know if just the unused data input pin should be grounded, or the unused clock and asynchronous input pins as well.
  
  Thanks.

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• #1 Reply
  Posted by Andy Watson on 26 Jul, 2015 07:00
• Yes, ground all unused inputs.
• #2 Reply
  Posted by Chris Wilson on 26 Jul, 2015 10:57
• Thanks for the fast replies. Someone on another forum has also answered another query, when I powered the circuit up with just the 12V low voltage circuits connected, and I was about to switch on my sig gen to replicate a TX from my transceiver, I noticed a poor sine wave of low amplitude on my scope. I couldn't understand how it was showing an oscillating signal without the sig gen connected. Now I know the likely cause! The CMOS stuff has a very high input impedance and floating inputs are prone to self oscillate
  
  The trip LED would also spontaneously come on after a minute or two of running with what appeared to be good square waves to the gates of the FET's. The FET's were not switching HV, in fact I have not assembled the RF side of the FET's yet. I am hoping this will also be cured by grounding the unused pins.
  
  Thanks for confirming which ones I need to ground!