RF voltage amplifier vs RF power amplifier.

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Osawa_Odessa

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Hi,
I want to ask some basic questions. I want to design a RF amplifier, my goal is to amplify voltage but in all documents they wrote "RF power amplifier".
I want to know if there is any difference between them. Can I use "RF power amplifier" to amplify voltage?
With "RF power amplifier" I see that they classify them into A, AB, B or C. How about RF voltage amplifier?
Note that I want to use RF amplifier for this project that I have stated here: https://www.edaboard.com/threads/293872/
 

You can't amplify voltage without also generating power if you have a finite load. The amount of power depends upon the load impedance. Typically RF amplifier circuit input and output impedances vary from 50 to 100 ohms so you can calculate the power generated as V^2 / R.
 

Main difference is input and load impedance. Power amplifier has usually 50ohm while voltage amplifier uses significantly higher impedances and they can be different. Power disipated on small load resistance require less voltage than the same power disipated on high resistance load. That's according to Ohms law.
 

All depends on your RF frequency. Above say 10 MHz, most test equipment uses a standardized line impedance of 50 Ohms, and all devices like amplifiers and loads have the same due to easy testing. We mostly refer to power in design and testing.

If you need a certain voltage to get at RF amplifier output, you can either use a RF transformer or a resonant circuit with a high Q. Also I can assume the load impedance should differ from the 50 Ohms. RF transformers are preferred as they are wideband, resonant circuits must be tuned to one chosen frequency.
 

RF voltage amplifiers are often wideband like analog oscilloscope vertical amplifier. They have upper frequency limit up to few hundred megahertz. First such amplifiers were made with tubes.
RF power amplifiers are practically all narrowband made for specific RF.
 

Hi Osawa
classification of RF amplifiers are not limited up to class C . you will see class D or S / E/ F too .
I think you need to start to read some books about RF circuits . for instance Secrets of RF circuit design by joseph j carr . or perhaps RF circuit design by chris bowick or .... etc
Best Wishes
Goldsmith
 

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