Path: ...!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!eternal-september.org!.POSTED!not-for-mail
From: Bill Sloman <bill.sloman@ieee.org>
Newsgroups: sci.electronics.design
Subject: Re: MOSFET Analog Switch Question
Date: Sun, 20 Apr 2025 21:51:27 +1000
Organization: A noiseless patient Spider
Lines: 25
Message-ID: <vu2n41$3np8k$1@dont-email.me>
References: <877c3fyj1k.fsf@librehacker.com>
 <cuu80kdc36tliia7fsprrrdp41kco46a36@4ax.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Injection-Date: Sun, 20 Apr 2025 13:51:30 +0200 (CEST)
Injection-Info: dont-email.me; posting-host="a01f12bb441905d8f29ce074a18b3533";
	logging-data="3925268"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX1+eH51CtMRrZZkA/q2WeWhWR6BuVr+QuKM="
User-Agent: Mozilla Thunderbird
Cancel-Lock: sha1:pQG9aQWK534+3Ous/7V4AlXCtQc=
In-Reply-To: <cuu80kdc36tliia7fsprrrdp41kco46a36@4ax.com>
X-Antivirus: Norton (VPS 250420-2, 20/4/2025), Outbound message
X-Antivirus-Status: Clean
Content-Language: en-US
Bytes: 2191

On 20/04/2025 2:46 pm, 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?
> 
> It should be symmetric, happy conducting in either direction.

Only in the sense of conducting both ways. N-MOSFets tend to be more 
conductive than P-MOSFets. If they make the P-MOSFets bigger than the 
N-MOSFets they can can balance the channel resistances, but not the 
channel capacitances.

> Don't let the signals go beyond the rails.

That would reverse bias the isolation diodes and feed current into the 
rails, and elsewhere if you are unlucky. The effects can  be unfortunate.

-- 
Bill Sloman, Sydney