RF coupling transformers

[Kevin Weddle]

Do RF coupling transformers ever step up or step down voltage? I have only seen them used in a few applications. Are they inefficient signal coupling devices?

 

[Hero999]

If you look at the impedance matching transformer article on Wikipedia, you should be able to figure it out for yourself.

 

[Kevin Weddle]

Impedance matching transformers don't match impedances at RF frequencies.  RF range transformers used for signal coupling are often step down transformers which increase load impedance, or they are used mainly for resonance. But they are hardly ever used in many circuits. Is it because they produce signal distortion?

 

[Hero999]

You obviously didn't bother to search Wikipedia as I suggested.

Next time I'll ignore you when you ask a question.

 

[Kevin Weddle]

I did a Wikipedia search for impedance matching transformers. Still, it is about impedance matching. I was refering to transformers used in the IF frequency ranges of audio and video.

 

[audioguru2]

IF transformers are old and are not used anymore. Higher performance and lower cost crystal filters and SAW (surface-acoustic-wave) filters are used for the past few years.

 

[Hero999]

Kevin,
Here are the articles I'm talking about. It doesn't matter whether it's RF or audio.

http://en.wikipedia.org/wiki/Impedance_matching
http://en.wikipedia.org/wiki/Balun

Pay attention to the formula. If you can't figure out whether an impedance matching transformer changes the voltage or not then you need to retake basic high school level maths.

 

[Kevin Weddle]

I have read the explaination for impedance matching and transformers. In what kinds of circuits are they used, and why use a transformer?