How to enhance output Voltages of this RF Power Amplifier

[nomi114]

TL;DR Summary

How I can boost the output voltage to the desired level i.e. 15~18Vpp.

Hello everyone, I’ve been working on modifying the RF Power Amplifier circuit, and I’ve made good progress (schematic is attached below). However, I’m now facing a small issue – I’m currently getting an output voltage of around 9Vpp, but I need it to be in the range of 15–18Vpp. I’ve tried changing the values of resistors R6, R7, and R8, but I haven’t been able to reach the desired voltage level. I would really appreciate any advice on how I can boost the output voltage to the desired level. Thanks in advance for your help.

 

[Baluncore]

Welcome to PF.

What is the application of this PA?
What simulator are you using? LTspice?
Attach your .asc file as a .txt file to your next post.

1. Increase Vdd.
2. Raise the output impedance of the band-pass filters.

 

[nomi114]

Welcome to PF.

What is the application of this PA?
What simulator are you using? LTspice?
Attach your .asc file as a .txt file to your next post.

1. Increase Vdd.
2. Raise the output impedance of the band-pass filters.

Thanks for your kind reply. This PA can be used for RFID Applications (Frequency range 7.7MHz ~ 8.7MHz). Yes, i am using LTSpice simulator, I tried to upload .asc file but fail. Sure, i will attached as text file for your perusal, pls. Thanks again Sir for your kind help.

 

[Baluncore]

Thanks, the .asc file works OK.

The filter should match the impedance of the MOSFET drain to the antenna.

Do you know the output impedance of the MOSFET drain?

Will your antenna really be 50 ohms, differentially fed, or will it be fed through two 50 ohm coaxial cables, to a 100 ohm loop antenna? That loop antenna could be tuned to advantage.

If you could combine the two MOSFET drains with a centre-tapped RF transformer, you would only need to build one band-pass filter, and feed one transmission line to the antenna.

Your BPF is smooth, but has about 10 dB of loss in-band, when driven with a 50 ohm source, and terminated in a 50/2 = 25 ohm load. I would be surprised if better matching of drain to BPF, and BPF to antenna, could not give you half of that loss back.

It is good practice to place the SI prefix in the place of the decimal point. That reduces the length of the text and eliminates some reading errors.

It is poor practice with LTspice to include the unit with the component value. One day you will place a one farad, 1F0 capacitor, that will have a value of 1x10^-15; a whole femtofarad. Units also make the use of evaluated {parameters} more difficult.

 

[berkeman]

This PA can be used for RFID Applications (Frequency range 7.7MHz ~ 8.7MHz).

What are the RF licensing and testing requirements for this type of device in your country? In the US, I believe I would need to do RF testing at a local test lab that has an anechoic chamber (or an open air test site out in the countryside) to ensure that my intentional radiator device does not exceed the transmit levels for in-band and does not have too high of a level of harmonics or other out-of-band energy. Will you be doing that kind of testing on your device?