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Re: LF: IEEE488

from [Alberto di Bene] [Permanent Link][Original]
To: [email protected]
Subject: Re: LF: IEEE488
From: Alberto di Bene <[email protected]>
Date: Sat, 12 May 2012 23:34:05 +0200
In-reply-to: <CAA8k23RrSSyN6DtTFG7vUFjAu4Qua9hYWwr3_KafPRQY+0ZGNQ@mail.gmail.com>
References: <A318522BCED445EAB5653B1E0996A0EB@computereebf79> <96F6DE3827714341B45E5194EA6D7946@AGB> <933D952DE28E4835A61D2B4B6F455CBF@computereebf79> <B024050ECD814C5AA6F0F4AB8A21CAE0@AGB> <CAA8k23RrSSyN6DtTFG7vUFjAu4Qua9hYWwr3_KafPRQY+0ZGNQ@mail.gmail.com>
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On 5/12/2012 9:41 PM, Andy Talbot wrote: 
 A JFET switch is probably the simplest.   Uses a P Channel device
like a 2N3820 so it can be controlled with a positive voltage.     +V
is device  off, 0V is switched on.  Which sounds a bit weird to
visualise   Used in shunt means a +Ve voltage switching it off gives
RF is on.  0V attenuates RF.  Rds(on) is a good few ohms, so needs to
be run in a Hi-Z system.  There are no doubt better P-Chan FETs.

Andy
'jnt
Or maybe the ubiquitous 2N7000 enhancement mosfet...  does not conduct with
the gate a 0V,  but it does when the gate is at +V

73  Alberto  I2PHD

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