EMRFD Message Archive 8080

Message Date From Subject
8080 2013-01-08 20:29:40 Kerry Transformer For Norton Amplifier
The Norton amplifiers described in EMRFD (2.27 & 2.28) and everywhere else I have seen assume a one-turn winding for the emitter section of the transformer.

What happens to the turns ratio if we use a two-turn winding for the emitter section?

My formal mathematics is very weak; I expect that many here can develop the equation that would replace the one-turn equation (M squared = M + N + 1) for the case of a two-turn winding

I have used "first principles" to calculate what I think is the result but it is not in a "mathematical" form and I end-up with non-integer values of M and N.

For instance, for a two-turn emitter winding, I get M = 2.8 & N = 7 / M = 4.2 & N = 15.4 / M = 5.6 & 14.

I'm not sure if the gain equation (G = 20 log M) still applies so I would appreciate some advice on that as well.

Over to the mathematicians amongst us!

Kerry VK2TIL.
8082 2013-01-08 21:27:32 Kerry Re: Transformer For Norton Amplifier
My attention has been drawn (thanks to my friend) to the fact that the matter of my enquiry is covered by Dallas Lankford;


I have this paper by Dallas; I just didn't think to look there.

I also have another paper by Dallas on advanced Norton amplifiers;


I thought I'd share these with the Group.

Now I will sit down and try to get my feeble brain around the more-than-one-turn design as explained by Dallas.

Kerry VK2TIL.
8083 2013-01-08 22:54:35 Jerry Haigwood Re: Transformer For Norton Amplifier
Hi Kerry,

The Norton amp is unique in that the turns ratio must be maintained. If
we take a standard Norton amp with a turns ratio of 1:5:3 ( a 9.5db gain
amp) and we want to double the 1 turn to 2 turns, then we must also double
the other two turns. So a 1:5:3 turns ratio becomes a 2:10:6 turns ratio or
a 3:15:9 turns ratio, etc. The gain will remain the same. The extra turns
are sometimes used to produce an amp at a lower frequency. I usually use a
FT50-75 core which has an AL value of 4200. This large value will let you
build a Norton amp at a fairly low frequency. I have a PDF file on Norton
amps I will send you.

Jerry W5JH

"building something without experimenting is just solder practice"

8084 2013-01-08 22:54:35 Jerry Haigwood Re: Transformer For Norton Amplifier
Hi Kerry,

In the first paper you mention below, Lankford mentions that it is
possible to build a CBTF (Common Base Transformer Feedback) amp using a 2
turn link on the emitter but keeping the other turns ratio the same such as
a 2:11:4 ratio. Dallas mentions this because of impedance matching. The 2
turn link would of course increase the input impedance. However, he
mentions that he has not characterized the 2 turn link and cannot comment
much about how it will act.

Jerry W5JH

"building something without experimenting is just solder practice"