RF transformer design
时间：04-09
整理：3721RD
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Hello all,
when designing a class A&AB RF amplifiers (for example for the range from 3Mhz to 30Mhz) using a transformer to match the laod to the transistor output impedence, the ratio of the turns can be easly calculated, but:
Q1) how the actual number of the windings is calculated?
Q2) in case the primary of the transformer is tuned , is the number of turns remains the same for the highest Q value of the tuned circuit?
Q3) what is the prefered transformer to use? is it the balun, transmition line transformer, classic transformer...?
thanx for any help
when designing a class A&AB RF amplifiers (for example for the range from 3Mhz to 30Mhz) using a transformer to match the laod to the transistor output impedence, the ratio of the turns can be easly calculated, but:
Q1) how the actual number of the windings is calculated?
Q2) in case the primary of the transformer is tuned , is the number of turns remains the same for the highest Q value of the tuned circuit?
Q3) what is the prefered transformer to use? is it the balun, transmition line transformer, classic transformer...?
thanx for any help
Seems that you are intending a wideband linear amplifier. It most likely shouldn't have a tuned transformer, but the output transistor(s) may have a frequency dependant impedance. Not an easy design!
Polyfet has a lot of interesting reference designs of this type, mostly using transmission line transformers. In any case, you should consider, that a RF transformer has a considerable leak inductance, it can be regarded rather as pair of coupled inductances.
http://www.frenning.dk/OZ1PIF_HOMEPAGE/AN749.pdf