All is in title, in fact, I would like to do a variable amplifier drived by arduino for RFID and would like to know how I might make this.
It’s for 13.56MHz (HF) coming from a “NFC Shield V2” so I guess a Class B amplifier will be sufficient, I’ve seen bipolare transistor (Class A) is nice for HF but have a bad efficiency ( < 25% ).
So which class and which power amplifier input to double (at least) the output HF signal?
A last thing, if I don’t use a “push-pull” pattern ( one transistor for negative part of signal and another for +) class B amplifier, my output would be in only one physical direction isn’t it? (one face of the antenna which is a panel design)?
Thanks in advance!