Miniature IF Transformers
Miniature IF Transformers
(OP)
Many AM (amplitude modulation) radios utilize 455 kHz IF (intermediate frequency)transformers. My company uses a similar circuit to amplify a single CW (continuous wave) signal in the 100 kHz to 500 kHz band. However, it appears that the IF transformers are becoming harder to acquire. At least the through the hole versions. I would like to design a narrow band circuit (overall Q about 100) to amplify a single CW signal. The circuit voltage gain would be in the neighborhood of 100 dB.
Thanks
Thanks





RE: Miniature IF Transformers
-- if youhave enough space -- you should make an TH to
SMD adapter.
RE: Miniature IF Transformers
RE: Miniature IF Transformers
To replace 2 transformers you need 8 reactive elements (R/C). You would prefer good selectivity and flat top
-- this is difficult without tuning.
if the data BW is low enough
after a single LC stage, mix it down to as low frequency as
possible using a xtal osc. and filter it there.
Else check out xtal or SAW filter.
RE: Miniature IF Transformers
RE: Miniature IF Transformers
RE: Miniature IF Transformers
You say you need a Q of 100, which defines the bandwidth (in conjunction with the centre frequency). IF stages use this high Q for selectivity. You are using it for noise suppression I suppose.
The question then becomes why you want a transformer at all? Can’t you just use a single LC resonant circuit to get the Q? You would probably want to use a pair of capacitors to give some impedance transformation.
Are you making a transistorised amplifier or an opamp circuit? I would think that this was a trivial job for opamps and that you would have to try quite hard to get good performance (linearity, gain, SFDR) with transistors. (You get a hell of a lot of transistors in opamps for not much money). The bias circuitry is clearly not needed with opamps so the circuit may well be cheaper and simpler using an opamp based design. We are talking about one quad opamp with 25dB per stage. Use an opamp that is not unity gain stable as you need a lot of GBW product.
RE: Miniature IF Transformers