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Class AB reference design

时间:04-06 整理:3721RD 点击:
This question may sound a bit elementry but better to ask when in doubt. I want to design a class AB linear PA operating SSB, CW, digital, etc in the HF bands. I would like to use NXP's BLF578 due mostly to the fact that I was able to procure a few samples at no cost, and their excellent efficiency.
My question is this: Is the provided(in NXP datasheet) test circuit suitable for this, without alteration, and assuming proper filtering after the PA circuit?

Getting this beast for free is good, when the price for each is about 400 bucks (initially was 600).
The ruggedness of this transistor is better compared to the counterparts from Freescale. The PCB recommended by NXP should be fine, I've seen once an working FM broadcast PA with this transistor using the recommended layout. I never seen an HF application with this transistor.
http://www.nxp.com/documents/applica...te/AN10800.pdf
At this high output power level very important is to follow strictly their recommendations for PCB material, mounting, soldering, and quality of components, which sometimes are hard to get.
On the other hand, the gain of this power transistor is higher than usual PA's, which makes things more complicated in terms of self-oscillations which can damage the transistor.
Anyway, you mentioned that you got "few" of them...so you have some room for mistakes...

only S313 from D-K now :p
http://parts.digikey.com/1/parts/183...lf578-112.html

Yeah, actually I said "about". Plus international shipping you get there. Here is equivalent of about S370:
http://uk.farnell.com/nxp/blf578/ldm...687?Ntt=blf578

This is good. The crisis make some things cheaper and cheaper. Bad that my car still runs on petrol.

Thanks for the reply- Assuming I can get this thing constructed; I intend to be extremely conservative as far as expectations for output power - an yes, another hurdle is sourcing the EXACT components specified by the MRFR.
Thanks again

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