Linear RF Power amplifier

[Chinku_420]

I have to design a Linear RF Power (class A). My frequency is 2.4 GHz. I need 25 dB gain. If I choose Pin= -20 dBm and the Pout should be Pout= 5dBm. Right?
If Pout id 5dBm= 3.162 mW. So, Rload will be 9/(2* 3.162m) = 1.43 kOhm. (Vdd is 3V & process is TSMC 180nm). So, should I transform this 1.43 k to 50 Ohm? Is this Rl and Ropt same?
I need your help. Thanks

 

[KlausST]

Rload will be 9/(2* 3.162m) = 1.43 kOhm

Where does the "9" and "2" come from? I don´t understand the 1.43 kOhms.

Usually the input and output power in dBm is referenced to the characteristic impedance. Usually 50 Ohms.

Klaus

 

[Chinku_420]

Where does the "9" and "2" come from? I don´t understand the 1.43 kOhms.

Usually the input and output power in dBm is referenced to the characteristic impedance. Usually 50 Ohms.

Klaus

Pout= VDD^2/(2 Rl).
Is that right formula?

 

[FvM]

You are apparently assuming an ideal class A output stage with output inductor, achieving 2*Vdd swing. I think that's completely unrealistic and no suitable way to design microwave amplifiers. Also 1.4k:50 ohm impedance matching is no good design idea.

 

[Chinku_420]

You are apparently assuming an ideal class A output stage with output inductor, achieving 2*Vdd swing. I think that's completely unrealistic and no suitable way to design microwave amplifiers. Also 1.4k:50 ohm impedance matching is no good design idea.

Thanks for the reply.

At this point, I am only doing calculations while assuming everything ideal. I know that the the drain inductor has very low Q factor. But, my question is how can I chose the load resistance with the same specs.

I know about the load-pull analysis and conjugate match concept. But at this point, I want to do the simple calculations.
Thanks