MC 13203 LNA transistor adaptation

[Francois]

Dear Gruppe,

We have an old design using MC19192 then after MC13203 Zigbee controler which work very fine.

It use also a 2.4 GHz Low Noise Amplifier based on transistor Freescale MBC13900.

This transistor is obsolete and we want to move to another one before redesigning the whole project.

Our design is moreorless similar to the Freescale Eval Kit.

It's decribed in details in document Document

Number: MC13192EVBRM

Rev. 1.1

05/2006

I've tried other transistors without changing the matching but range decreases and sometimes, I can see oscillations.

If I want to change the Rf transistor, I have also to change the Rf adaptation at input and output of this transistor.

In the document, at the end of page 3.3 and beginning of page 3.4, it's indicated that the Z parameters for MBC13900 are

36+j21 Ohm at the input

and 64-j70 Ohm at the output.

With these values, it's not difficult to calculate the adaptation.

My question is : how are calculated these values ?

I can not find from where these values are comming.

I've tried to transform the MBC13900 S parameters to Z parameters with without any success.

For Vce = 2 V, Ic = 3 mA, f = 2.4 Ghz

f S11 S21 S12 S22

2.4 0.472 -166 3.778 66 0.077 25 0.554 -48

I've tried with RfSim99 but again, not the same values.

Are those values comming directly from in situ measurement on the board or from another calculation?

Any help would be welcome

Regards

francois

[Francois]

Hello Stanislav

Thank you very much for the response.

I don't want to redisign the whole circuit but I'm open to change the matching components.

My problem is that I have several designs witch are supposed well adaptated :

     Freescale MBC 13900

     NXP BFU725 N1

But I've spent hours, and I'm unable to recalculate the matching circuits, perhaps it uses measurements results that I don't have and can not measure.

As you suggest I'll explore these two directions :

    1 ) Try with avago ATF-55143 which is available at Farnell, Investigation very easy to do

     2) Try to find the closest S parameters from the Freescale design in the following parts

      Infineon BFP420

     Avago ATF-55143

     NXP BFU725P N1

     Eventually, if needed I can slightly change the polarisation ot the Vce as consuption is not critical.

Thank you and best regards

francois

[Stano]

Hello Francois,

I understand your requirement not to redesign your whole application. I would like to suggest you solution with minimum effort for tune the LNA circuit.

I know that MBC13900 has no direct replacement, but the closest transistor with very close parameters, which could be used is ATF-55143. If you set up the working point to Vds = 2.7V and Ids = 10mA, the S-parameters are similar to those you mentioned. This replacement provides better noise parameters. The datasheet not comprises impedance chart, but comprises the detail ADS model. You can try it to set up the matching circuit.

The datasheet is available on:  http://www.avagotech.com/products/wireless/transistors/fet/atf-55143

I hope it can help you.

Best Regards,

Stano.

[EarlOrlando]

Hello Francois,

As you said, the parts that you are using are very old so they are not supported. Also, the transistor that your design needs doesn't have a replacement. My advice is to move to the Kinetis KW2x 2.4 GHz RF MCUs​ and I recommend you to take a look into the KW2x Reference Designs​.

Best regards,

Earl.