Why use transformer in RF circuit?

I know use it as impedance transform like 1:4 or 1:1..
Another reason for this?
Also, we can use L,C network to do match ..

These transformer impedance ratios are broad band, frequently several decades wide.

Not only that the transformers can be used for broadband impedance matching (especially with high ratio) but they can also be used in effective conversion from single-ended to differential configuration and vice versa.

So, what's difference between transformer & balumn?
it looks like the same function..

They can be used for interstage coupling(to match impedances for max power tranfer) in RF amps and also pass DC to bias devices when necessary. Lots of examples on the net.

Hi All,

adding on to this discussion, may I ask how RF tranformers are also used as potential divider in circuits at lower freq, say 50MHz?

It's something like we want max voltage transfer eg into a high Z device like op-amp,FET, instead of max power transfer which is the case in most RF 50Ohm systems.


Thanks!

Any reply? :)

Baluns are not as expandable as transformers. Matter of bandwidth.