[sdiy] S&H question

[James Patchell]

Depends on how you define better...

The advantage of the bilateral switches is that they have a low overhead, 
in that you do not need to make a bunch of level shifters and other 
nonsense you need with an J-FET.  Now, one important parameter you need to 
look at when considering a switch is also the leakage current.  So, you 
will need to consider this as well.

Now the switch I am most satisfied with is a descrete MOS-FET, but you need 
to find one that has the substrate brought out on a separate pin so you 
won't have problems with that pesky parasitic diode.

Generally though, I use a bilateral switch...I use the DG201 personally, 
but there are others.

At 05:05 PM 11/28/2004 -0700, Scott Juskiw wrote:
>Looking at some old schematics I see that many sample and hold circuits 
>use an n-channel FET (typically 2N3819) to sample the input signal. When I 
>look at more recent schematics I see these new fangled bilateral switches 
>(CD4066 or DG213) or purpose built S&H chips (LF398) being used instead of 
>a FET. I've only used a FET in the past and have been reasonably happy 
>with it. Are these bilateral switches or LF398 really that much better? 
>The application is a ribbon controller.

         -Jim
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