From: Peter Chadwick <Peter_Chadwick@mitel.com>
To: "'W8JI@contesting.com'" <W8JI@contesting.com>,
"'amps'"
<amps@contesting.com>
Subject: RE: [AMPS] PIN stuff
Date sent: Fri, 4 Jun 1999 15:14:41 +0100
>
> Tom says:
>
> >If you place the PIN diodes in parallel, place them in OPPOSITE
> >polarity for RF but in series for RF.
Woops, that's right Peter. It should read in parallel for RF but in
series for DC.
>
> I think Tom actually mean in series for DC. Bearing in mind that the
> forward RF resistance in the diode is of the order 0.1 or 0.2 ohms, then
> the series resistance of external parts will tend to dominate. Thus
> playing around with parallel for RF and series for DC will tend to move
> the dominant losses to the external components.
Chip caps are well down in the milliohm range, but if you use them
you need to add external resistance to equalize currents.
As a matter of fact, if you parallel diodes you always need to add
controlled series external resistance a bit larger than the diode
resistance to equalize diode currents.
Since you need all that anyway, you might as well reduce supply
demands while you are at it.
73, Tom W8JI
w8ji@contesting.com
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