Re: MOSFET Analog Switch Question

On 2025-04-20 00:46, john larkin wrote:

On Sat, 19 Apr 2025 12:48:23 -0800, Christopher Howard
<christopher@librehacker.com> wrote:
 

Hi, I have some DG212BDJ Quad SPST CMOS Analog Switches. I am wondering
if there is some significance, for each switch, to how the source and
drain pins are used/fed. The data sheet says Analog Signal Range
(V_Analog) is +/- 15 V, so it doesn't matter which way the current is
moving across source and drain pins, right?
>
>
Christopher Howard

 It should be symmetric, happy conducting in either direction.
 Don't let the signals go beyond the rails.

Yup.  Otherwise, typically all the channels will get connected together by way of the substrate.  It's a puzzle to debug, the first time it happens to you--it's always the channel you're not focusing on that's railed. ;)
If you're worried about linearity, do note the switch resistance vs. signal voltage curves, which are usually sort of moustache-shaped.
To avoid signal distortion, don't draw significant current through an analog switch.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510
http://electrooptical.net
http://hobbs-eo.com