EMRFD Message Archive 8080

8080 2013-01-08 20:29:40 Kerry Transformer For Norton Amplifier Message Date From Subject 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. My attention has been drawn (thanks to my friend) to the fact that the matter of my enquiry is covered by Dallas Lankford; www.thegleam.com/ke5fx/norton/lankford.pdf 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; www.thegleam.com/ke5fx/norton/norton_rohde_lankford.pdf 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. 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" 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"