Richard Clark wrote:
I've seen some discussion that it doesn't matter because front ends
only take voltage and need no current. This is a 0Hz analysis and at
10MHz is thoroughly dead in the water.

Once again, what I said has been thoroughly misquoted.

Stray capacitance negates any claims to an input being Hi-Z and the
whole point of low Z inputs is to swamp nature's capacity to send your
signal straight to ground before it sees that amplifier.

Now that analysis really *is* dead in the water!

My simplification to "the amplifier takes what it needs from a 50-ohm
source" is just that - a simplification. But it is based on actually
knowing something about the subject. If you wish to discuss input
network design for FET RF stages in terms of Smith-chart circles of
constant gain and noise figure, and the device manufacturer's quoted
data for gamma-opt, then I'm willing and able.


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

On Mon, 16 Aug 2004 23:06:43 +0100, "Ian White, G3SEK"
wrote:

Richard Clark wrote:
I've seen some discussion that it doesn't matter because front ends
only take voltage and need no current. This is a 0Hz analysis and at
10MHz is thoroughly dead in the water.

Once again, what I said has been thoroughly misquoted.

Hi Ian,

If it was you that said it, otherwise you are misquoting me.

My simplification to "the amplifier takes what it needs from a 50-ohm
source" is just that - a simplification.

Ah yes, you are misquoting me.

73's
Richard Clark, KB7QHC