Re: LF: IEEE488

[Alberto di Bene <dibene@usa.net>]

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