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The Designer's Guide Community Forum › Design › Analog Design › Pass-gate behavior when switched off
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Pass-gate behavior when switched off (Read 3969 times)
skapc66
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Pass-gate behavior when switched off
Aug 03rd, 2009, 6:16am  
With reference to attached picture
If I connet a voltage generator (V1) to a pass gate switched off (V2>V1) I see that the other passgate output Vx follows the input (example being V2=2V, I get Vout=1.3V if V1=1.7V and Vout=1.5V if V1=2V). Cannot understand why. Could you help?
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raja.cedt
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Re: Pass-gate behavior when switched off
Reply #1 - Aug 3rd, 2009, 6:47am  
hi,
   check the ckt properly, i think you pmos is still passing signal so please check wether you have connected proper vdd to that or not?

Thanks,
Rajasekhar.
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skapc66
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Re: Pass-gate behavior when switched off
Reply #2 - Aug 3rd, 2009, 6:53am  
I checked once more, all the connections are as in the picture I attached.

Rgds
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salty
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Re: Pass-gate behavior when switched off
Reply #3 - Aug 3rd, 2009, 8:30am  
Do you have anything tied to Vx?  Other that the 2 transistors?
Try this if not, put a 1MEG pulldown and see what it does.
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skapc66
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Re: Pass-gate behavior when switched off
Reply #4 - Aug 5th, 2009, 11:36pm  
I had an inverter input connected to Vx, but the Vx value remains the same even if I disconnect it.

Rgds
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raja.cedt
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Re: Pass-gate behavior when switched off
Reply #5 - Aug 6th, 2009, 12:08am  
hi skapc66,
                what i feel you don't see any difference in the voltage magnitude..but i am sure you could see the delay...what you do is increase the inverter size...now you feel the difference.

thanks,
rajasekhar.
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salty
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Re: Pass-gate behavior when switched off
Reply #6 - Aug 6th, 2009, 8:05am  
Is this from a transient sim or DC sim?
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raja.cedt
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Re: Pass-gate behavior when switched off
Reply #7 - Aug 6th, 2009, 10:16am  
hi,
   ya do tran only for all digital ckts.......

thanks,
Rajasekhar.
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