Dear Christy,

as this is really not a new subject you may first look around in the literature (e.g. via IEEE explore access and abstracts there is free but not download of most papers) what has been done already and in which particular way of implementation and what is already on the market. When you talk about 3G /4 G the term wideband is relative. Is this amplifier to be used in a base station or in some portable device. For power devices you need nonlinear optimization (I hope your supervisor is aware about that) which is quite a challenge both hardware wise and numerically. Good luck

You can start by Microwave and Rf Design of Wireless Systems(David M.Pozar) to understand the principle and after that you can choose your class and type of amplifier, and the most important the matching network.

Hi Christy Abhi ,

Some say "PA design is a black magic", well it is not.

1) Read and understand the basics of power amplifier (PA) design. You can have a look on

Research A Ka-band power amplifier design for satellite communication...

2) learn ADS design tool (its normally free for students). They have nice templates to start from the basics.

3) Whether you are working on MMIC level or discrete transistor, KNOW your TRANSISTOR first. What is allowable VDD/VCC, Id/Ic, IV-curve, intrinsic gain, maximum frequency (fT or fMAX), thermal issue?

4) Start from the selection of the operation or class of power amplifier for your application. How much your application allows to operate your PA at the suppression? What Power added efficiency PAE you need? For GSM 3dB suppression is fine so you can even chose near to class B operation and PAE is also near to its peak. The non-constant envelope modulations, such as AM or combination of amplitude and phase modulation (e.g QPSK/QAM/OFDM/SSB) need a linear class of operation (class A or AB).

5) Once you know the class of operation (basically selection biasing point and have a rough idea about how its large signal covers in IV curve ), DO NOT start designing PA aiming high gain, high pout, and efficiency in the first place. Start from a simple single stage PA. What PA stands out form rest of amplifiers that its output impedance consideration. Its output matching network OMN is designed such a way the it is matched to the output impedance corresponding to the maximum output power (not max gain) of the output of the transistor. Most of the PA designer sweat during their OMN design. Next, design input matching network for gain-input impedance matching.

6) From my experience having good power matched output and gain matched at input gives you good gain (for the selected operation). You can tune little bit and get better PAE and Pout.

7) Once you simple single stage PA, try even higher output power using cascoding PA or power combining PA. Cascoding PA improved Pout and also Gain. Power combing PA need good power combiner. You can even try mult-stage PA (connected two PAs serially with interstate matching). You will loose PAE generally when you chose more complex PA configuration. Wide band amplifier design is a whole new topic, one of the common practices is to use transimpedance stage but its effort is significant specially adapting it in PA. Otherwise, for wide band you can still tune your OMN or use smooth transmission where there is sharp impedance transition in the layout or use radial stub if you have stub in your layout.

Hope it helps,

Amit

Amit Shrestha thank you for your explanation. Can you help me with the 3rd step about how to find the proper transistor for wide band application and about finding the biasing point and etc. Can we get it from the data sheet of the transistor or ??

Christy Abhi So you are using discrete transistor for your PA, not MMIC.

3a) decide which transistor you want to use.

one example is to nxp transistor (see BFU610F), whcih has fT of 40 GH more thany enough for your 2-5 GHz application

https://www.nxp.com/parametricSearch#/category/c250_c854_c864_c1545

3b) In datasheet you find the transistor parameters, this is a bipolar transistor (you can search HEMT/CMOS transistor as well ). know transistor's Ic vs VCE, gain and output power limitations. Search transistor from nxp or other vendors that suits your freq and power

@Amit Sresht

I've decided to do the Rf power amplifier for boost the cellular signal within the range of 0.8GHz to 1GHz. And also decided to use the GaN FET model transistor. Can you help me with this type of transistor and this perticular design I choosed to do.