bfp405 lna

Hello,

I want a tutorial about the design of BJT LNA, i want to build it with discrete components at freq. ~ 100MHz,

I may use 2N2222 or 2N3904, or anyother suggested BJT..

Thanks for help,
Ahmad,

I am not quite sure, but I think the design will not be different from an integrated counterpart. Most probably, you will use the degenerated common source configuration ( very popular/ low noise ). I think the book "Radio frequency Integrated circuits" by John Rogers can help. Send me a PM if you need it.

Use BFW series bipolar transistors of Philips that introduce very low noise at that frequency.
Neither 2222 or 3904 is not RF transistors.Those transistros can be unstable at some frequency with certain configurations..

i have used 3904 to do RF amp in 100MHz range it gave about 14.5 db power gain
but it took alot of tuning

khouly

Hello all

I found recently the 2SC3355 low noise transistor (vendor is NEC) , and used it to build a 39dB gain LNA with NF≈ 0.9 at 100MHz ...

Thanks to Khouly who guided me through ADS noise matching via Smith Chart tool :)

Thank you all for help,
Ahmad,

i would say..BFP405, BFP520 and BFG403W would be a good choice for your design...especially BFG403W is a good choice...using smith chart (plotting gain and noise circle)...you can get very good result. I have used it for discrete LNA design, and have to admit it was a very good performance..so try it (BFG403W)

Yeah, 2sc2255 is a good choice. I have used it many times. There are also many vendors producing this transistor.

How to select the transistor if I want to design 2.4GHz LNA,any design guide?
Thank you in advance.

You can use BFG403W, it work well upto 16GHz (its unity gain frequency)...

also u can use BFG425W it is very good

and there are alot off applications notes
check this
http://www.semiconductors.philips.co...BFG425W_4.html

also try avagotech "agilent"
HEMT atf35143

khouly