rf2155 usage
Does output matching network affect P1dB point of a PA? I use RF2155 as the last stage power amplifier in my design of a cordless phone. The saturated output power now is about 21 dBm which is still far from my goal, 30 dBm. I know the frequency range I use, 268 MHz, is not included in the datasheet and 30 dBm power output is over the typical power output from datasheet. But, I'm thinking that if output matching network can change the P1dB point of a PA, then I still have some chances to use RF2155 in my design. Is it possible?
Thank!
In generally this type of amplifiers have own "light" ouput matching circuits that may give specified output level which is mentioned in their datasheets.Therefore, changing output matching rather than specified one will also change amplifier performance.
Because High Power amplifier concept is very critical design and needs many critical parameters such optimum load,efficiency considerations,output handlig etc.
In brief, if an RF power amplifier specifications are expressed in certain frequency band and performance was expressed under some conditions, these conditions must be supplied at all.
Otherwise,some degredations will occur..( with especially RFMD amplifiers..pff)
Yes the output match is very improtant.
A few things to keep in mind are:
If you're not in the specified freq range don't expect the same performace.
You might still be able to get the same performance but don't expect it!
As you change o/p match you will most likely trade off gain for power.
So now if you had: 15dB Gain and P1dB = 25 dBm (due to freq shift)
Atfer changing your match, you might expect a 12 dB gain and 27dBm P1!
And you will now need to have 3dBm more input power to your PA to reach
the P1dB point.
Hope this helps
Sounds like you are redesiging RF2155 for your application. It is gonna to be difficulty to get 3dBm additional power out of this device; I would suggest you pick up another device with right requency and power spec.
Good luck
Hi,
You can be sure that output matching have effect on P1dB.
Read next article
David
Yes. The output match can effect the P1dB, but this could low yor effiency which is very important in handset design just as what you are doing.
Normally, you would load pull the PA, plot the load pull-Pout circles on the smith chart and it will tell you if you can ever achieve the output you desire or if the effort is futile.
Hi, No way you will get 30dBm out of this device !. Better use a BLT81, is cheaper, smaller and gives you 1 Watt output power with NO problems.
Paul.
Added after 3 minutes:
Or BLT50 for VHF/UHF band !
Really thanks for your suggestion. But my voltage source is form battery. So, the PA will work in 3.6 to 4.2 voltage range. The BLT81 and BLT50 need 7.5V.....
Hi, You can power the BLT50 direct from 3.6 V no problem, output power will be a little bit lower but still more than you need I think.
Did you check www.hittite.com thought they had a nice chip SOT89 1.6 Watt Amp.
Paul.
the output matching network(OMN) does affect P1dB. OMN affects the output impedance of PA.There are some special impedance matching such as power matching,linearity matching and PAE matching and so on.