[sdiy] SYASH up!

[Ian Fritz]

Hi Eric --

At 02:14 PM 2/26/06, Eric Brombaugh wrote:
>I've not seen OTAs used as current switches -

They can and have been used as current switches in Tri osc cores.  Also as 
the Schmitt triggers.

>does the output of the 13700 have any leakage current that contributes to 
>the droop?

Some, of course, but very small.  According to the app notes, the output 
impedance in the off state is over 10^9 Ohms.  According to the data sheet 
it is ~10^11 Ohms at Iabc = .1 uA.  The 1 M resistor in my circuit is 
necessary to turn the OTA off hard.

>Just wondering if an OTA switch has any inherent advantages over a more 
>traditional CMOS switch like the 4066 or 405x types.

I didn't look into detail at the difference.  The leakage, charge transfer 
and series R of the switch would have to be looked at carefully.  Also 
voltage limitations.

For me, a big advantage of using the OTA switch is that I bought large 
batches of OTAs and selected out the best performing ones for critical 
applications, so I have a big stash I can use for less critical 
applications.  I consider them as pretty much free for applications like 
this.  :-)

Thanks for your interest!

   Ian