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Design >> Mixed-Signal Design >> buffer bandwidth in sample-and-hold
https://designers-guide.org/forum/YaBB.pl?num=1136065628

Message started by steven on Dec 31^st, 2005, 1:47pm

Title: buffer bandwidth in sample-and-hold
Post by steven on Dec 31^st, 2005, 1:47pm

I have a question on the buffer bandwidth of sample-and-hold circuit. Assuming that the S/H circuit operates at very high speed, then the buffer should have enough bandwidth to support it. If only focusing on bandwith of the buffer, what kind of buffer amplifier structures can be good options?

Thanks

Title: Re: buffer bandwidth in sample-and-hold
Post by Paul on Jan 2^nd, 2006, 2:22pm

Hi Steven,

for very highbandwidth, try to minimize the number of parasitic poles. Single-stage structures are most adequate for this. Especially folded-cascode amplifiers provide relatively high gain with a convenient gain-bandwidth product. Also check slew-rate performance, as it may limit the speed of your S&H structure.

Paul

Title: Re: buffer bandwidth in sample-and-hold
Post by steven on Jan 2^nd, 2006, 9:39pm

Hi Paul,

Thanks for your helpful message. Maybe there is some more to explore here: when facing a choice between folded cascode and telescopic structures, what are the major considerations you would take into account?

Thanks again.

Title: Re: buffer bandwidth in sample-and-hold
Post by Paul on Jan 4^th, 2006, 1:13pm

Steven,

the telescopic structure has only half the power consumption than the folded cascode topology (due to the absence of the folded branches), but it has a lower signal swing, both at the input and the output. I think telescopic structures are less frequently used in advanced technologies due to reduced supply voltages.

Paul