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Design >> Analog Design >> replace an ideal switch with transmission gate
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Message started by sara66 on Nov 16^th, 2015, 7:01pm

Title: replace an ideal switch with transmission gate
Post by sara66 on Nov 16^th, 2015, 7:01pm

hi every one
I want to replace an ideal switch with transmission gate ,I want to know how can I replace ideal switch with transmission gate?
I just measure on resistance of transmission gate ,if this on resistance is equal to closed switch resistance,it means they are same?
Thank you so much

Title: Re: replace an ideal switch with transmission gate
Post by loose-electron on Nov 17^th, 2015, 10:52am

depends on frequency and voltage range.

A transistor used as a switch has limitations of resistance, usable voltage range, and parasitic capacitance.

That's the simple answer.

Title: Re: replace an ideal switch with transmission gate
Post by DanielLam on Nov 18^th, 2015, 8:37am

1) For resistance: Sweep the input voltage range vs W/L to see if you can even meet the resistance requirement
2) For frequency: The transmission gate will add parasitic capacitance onto your nodes, so make sure the par. cap. is not significant at the W/L you choose
3) How much charge injection can you tolerate? This will depend on the clock edge steepness, input Vcm, device sizes, and load capacitance.
4) Decide on how to make clockbar. Can you use just an inverter? Or do you need to equalize delays -> related to charge injection in (3)