PS...ENI was a Rochester NY company, and RF Comm and ENI tech talk
intermingled as the tech's were friendly. One of my tech's had a wife
who worked there. We bought many of their amps to use in testing our
designs. Everything was open in those days, but ENI moved out of
Rochester as got too big/new management, to New Jersey .
I had built many transistor amplifiers way back in the 70-80's.
Good elaboration; I was terse. 73's K 2 L B
Alex Eban wrote:
> Most RF power transistors have a highly reactive, usually capacitive at HF,
> input impedance.
> This is in addition to the resistive part of the impedance being highly non
> linear: it takes values from infinity when the transistor base junction is
> reverse biased and about 1 ohm or so when biased forward. This resistor-
> called a swamping resistor, by the way- does just that: it tends to equalize
> the input impedance of the transistor across the range of resistance change.
> It can be used as part of the bias network, but it's not usually done, and
> definitely not in a class C amplifier.
> 73 and all the best:
> Alex 4Z5KS
>
> -----Original Message-----
> From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
> Behalf Of Herzog
> Sent: Wednesday, April 29, 2009 6:05 AM
> To: Ham-amps
> Subject: [Amps] purpose of 3 ohm resisters between base and emitter?
>
> Parasitic oscillations is a valid guess, and better than to just load
> both sides of the sine-wave drive. Biasing could be another valid guess.
> Quote:
> `Date: Tue, 28 Apr 2009 07:04:31 -0700
> From: Dan Sawyer <dansawyer@earthlink.net>
> Subject: [Amps] purpose of 3 ohm resisters between base and emitter?
>
> All, I have an ENI power amp with what look like SD 1726 transistors in
> a class C configuration. The circuit is pretty standard, however there
> are 3 ohm resistors between the base and the emitters. Can some
> speculate on the purpose of such a low value? It is common for resistors
> to be used in this configuration however they are usually a larger value.
>
> Thanks for your thoughts on this - Dan kb0qil
>
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