bjt microstrip biasing circuits

For Biasing just do a DC circuit analysis and you will know where your
Base & Collector Voltages are, that will determine what the S-Parameters
will be.

In photo 1, you must know what the Ic of the BJT is so you can know what
you collector voltage will be (Vc = VCC - Rc*Ic), Then your

Ve = [Ic+(Ic*(1/β)]*Re

Then set your R61 & R62 to be Ve +.65V....

Vb= Vcc (R62/(R61+R62)); Vb=Ve +.65V

Photo # Assumes you know the Bias Voltages of that BJT and you will apply it.
(Ib ≈ .5 - 5 mA so --> Vs - (50Ω * .005mA) ≈ Vs-.25V

If you need further help you should go re-read your Microelectronics book or
google "BJT Biasing equations"

Cheers

yes i do understand but can you tell me how to doo the biasing for attached diagram

yes i can doo biasing calculation but how do you impliment it on microwave circuit,like one in my previous diagram

rgds
jagath

Added after 20 minutes:

It is not clear what you want help.Add you bias componts into the photo attached Or...

what i want is how do i bias the BFG425W BJT in the
diagram,in clear words how do I implimenta normal biasing circuit on a microstrip

http://www.zen118213.zen.co.uk/RFMic...s_Circuits.pdf

what i want help on is,I have done the i/p and o/p matching network for LNA microwave amplifier,but how do you bias the transistor?
is it that you have to doo a separate normal ciruit for biasing and supply the voltage to the microstrip circuit through wires or do i use lumped components and design a bising circuil in the microstrip board it self can some one help me with this

rgds
jagath

You build a bias circuit with lump components then attached its outputs to the base and collector of your transistor. If you use RFCs in front of your bias circuit at the base & collector of your transistor, then you do not need to worry about the trace width and length of your bias traces. Just to make sure the RFC resonant freq is higher than your operating frequency.

hii it seems like you know better can you help me out further plese appreciate your help

rgds
jagath

if u r using ADS for simulation u can design a bias network for the BJT very easily as it has an in-built function that does that...u can use lumped components for the bias network design...as for your doubt whether to use microstrip...well...the bias network is a dc network so u can use lumped components like resistors etc...you just need to provide a ground to the RF signal in the bias network...hope this helps..

dielectric resoantor for DRO from www.accutemicro.com

The aim of any biasing circuit in MW circuit is to isolate DC part from RF part.

As you use blocking capacitors at i/p and o/p terminals to prevent DC from
reaching there.
similarly you should design your bias circuit in such a way that RF sees open
there or it gets attenuated if it enters there.
So you can use an RFC in series + shunt capacitor for making a bias circuit.

If your design is for microwaves,use a high impedance quarter wave line
in place of series RFC and a quarter wave length open stub in place of shunt
capacitor.

I mean quarter wave length at operating frequency.

I hope it helps.