Power Amplifier Designed for 8.2MHz

Thread Starter

Mike2526

Joined Nov 10, 2020
34
Please download your last file in LTspice format (*.asc), which you used for the simulation.
Dear Bordodynov,
There is little change at load resistance, before i used 2 separately load resistance (50ohm, 50ohm) namely as (R11 & R12) while now only one load resistance (R11, 50 ohm) is used. After changing this configuration i am facing problem.

Let me upload (.asc) file for your kind perusal please.

Regards
 

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Bordodynov

Joined May 20, 2015
3,188
I should have emphasized right away that your filter gives a lot of power loss. You took the easy way (this is bad) and created a filter with resistors on the input. And this is not all bad. You calculated a small time interval. I did the calculation up to 1000 µs and saw that the output power drops quite significantly over time. 1000 µs isn't enough yet.
 

Thread Starter

Mike2526

Joined Nov 10, 2020
34
Looks like low frequency ringing in the output filter, it should damp out eventually if you let the simulation run long enough.
Dear Sir,

Thanks for your nice observation, kindly suggest me how can i eliminate this issue & get a stable power level at output.

Looking forward to see your prompt reply please.

Regards
 

Thread Starter

Mike2526

Joined Nov 10, 2020
34
I should have emphasized right away that your filter gives a lot of power loss. You took the easy way (this is bad) and created a filter with resistors on the input. And this is not all bad. You calculated a small time interval. I did the calculation up to 1000 µs and saw that the output power drops quite significantly over time. 1000 µs isn't enough yet.
Dear Respected Bordodynov,

First of all i would like to say thank you very much for your kind help and time. Secondly, you are absolutely alright there's lot of power loss with the passage of time. so what you have suggested, i am little bit confused, can you highlight on the schematic where i need to modification & which components can replace with Resistors. I shall be highly grateful to you for this act of kindness..

Anxiously waiting for your kind and prompt reply.

Regards
 

Bordodynov

Joined May 20, 2015
3,188
Generally speaking you need to increase the values of resistors R9 and R10 to 100 - 200 Ohms. And the filter should perform two functions - filtering and impedance transformation. But this is not easy.
 

Thread Starter

Mike2526

Joined Nov 10, 2020
34
Generally speaking you need to increase the values of resistors R9 and R10 to 100 - 200 Ohms. And the filter should perform two functions - filtering and impedance transformation. But this is not easy.

Dear Respected Bordodynov,

Thank you very much for your help and kind cooperation. You are absolutely alright that i wanna use this filter for both purposes (i.e filtering & Matching) it's really hard task, i agreed with you. I will work on it and update you soon, again thank you very much..

Here i wanna another question that, our design is most appropriate for which type of the power amplifiers;

1. Pus-pull class E power amplifier with balanced FETs.
2. Differential cascode class E power amplifier.
3. Cascode class E power amplifier .
4. Power combining architecture.
5. self bias casecode class E power amplifier.


Regards
 
Last edited:

Thread Starter

Mike2526

Joined Nov 10, 2020
34
I would like to help but @Bordodynov is already on the job and I don't want to interfere with the master.
Dear DickCappels,

First of thank you very much for your kind concern. Secondly, no doubt @Bordodynov did lot of help for me, maybe he is busy now. Sir, if you reply me the query mentioned at post #30 then i shall be highly greatful to you for this act of kindenss.

Regards
 

Thread Starter

Mike2526

Joined Nov 10, 2020
34
Prably the dissatisfaction wind is blowing from the wrong impedance?? Did U checked Z11 and Z22 complex values??
Dear Sir,

I didn't checked, Actually i am afraid how to calculate these values from LTSpice ? Secondly i wanna ask that how can we draw the graph for efficiency and graph for Power Added Efficiency (PAE). Please guide me ??

Regards
 

DickCappels

Joined Aug 21, 2008
10,246
Here i want another question that, our design is most appropriate for which type of the power amplifiers;

(some text removed for clarity)
1. Pus-pull class E power amplifier with balanced FETs.
2. Differential cascode class E power amplifier.
3. Cascode class E power amplifier .
4. Power combining architecture.
5. self bias casecode class E power amplifier.
Edit: Push-pull class E power amplifier with balanced FETs, but only if driven that way.
 

Thread Starter

Mike2526

Joined Nov 10, 2020
34
Dear all,

hope every one is doing well with good health. here i would like to ask how can i adjust the smoothness of the filter response for upper matching network only(load+, load-) don't consider lower ckt please, i did many attempts but failed to do this(at such values). if somebody can help me in this regard i shall be highly grateful to him/her.

For reference screenshot and .asc is attached ..

looking forward for your kind response please.

Regards
111.png
 

Attachments

Thread Starter

Mike2526

Joined Nov 10, 2020
34
I changed the scheme a little bit. I increased the supply voltage. Of course, my filter is not very good. Look at this:View attachment 226721View attachment 226722
Dear Respected Bordodynov,

Thank you very much for your kind help. i don't have enough words, how to appreciate your kindness. every time you help me lot, and i found the solution & resolve my all worries/problems. here, i just would like to mention that the solution you provided for filter ckt, i must need to use R9 & R10 of 27K ohm not 100 ohm. With 50 ohm and 100 ohm RESISTANCE results are satisfactory but with 27K couldn't get stability and flat response for 7.5MHz ~ 8.7MHz. I need to have stable respone with these values. I shall be highly grateful to you for this act of kindness if you can do something for me please.

Regards
 
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