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basic LNA power related doubt (Read 470 times)
ezekiel1983
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basic LNA power related doubt
Mar 26th, 2017, 11:30pm
 
I am a mixed signal engineer .
i am trying to learn RF
Can you please help me with 2 doubts for which i was not able to see any answer anywhere.

is my assumption right that an LNA or an PA crossing P1db  due to an input drive, saturate eventually and start clipping the o/p waveform like normal opamp based amplifiers ..
in that case if the LNA is hard saturated by a CW of lets say 1616 Mhz  can it still amplify a 1600Mhz component of lets say -120dbm..
i understand if the modulation is phase or frequency ..a saturated amp may still help convey message ..but the point is what if the saturation is because of  different spectral component (in our case 1616 Mhz)and we are talking about demodulating a different carrier (in this case 1600Mhz)



The second one

AV02-2812EN DS MGA-22103 28Jun2011

media.digikey.com

MGA-22103 2.5-2.7 GHz WiMAX Power Amplifi er Module Data Sheet Description Avago Technologies MGA-22103 power amplifi er module is designed for mobile and fi xed ...



for the above part which operates from 3.3 volts ,p1db of 31dbm is claimed on datasheet  to a 50ohm load ..that would mean the voltage is about 22 volt peak to peak.how is this possible as drive power is only 3.3 volts

other than  a resonant amplier with high q how are they achieving this ?

Is there any class of operation which can do this ?



Regards

Eze
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chethan_RFIC
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Re: basic LNA power related doubt
Reply #1 - Apr 26th, 2017, 8:06am
 
Hi EZe,

Most probably this is the answer for your second question. Output of PA is given to some matching network that will boost output voltage and decrease your current. it is like cheating the circuit.

if u go through the matching networks u can understand this concept. mostly when we tried to match the high output impedance devices to 50ohm devices impedance  transformation done with matching network, same time voltage and current transformation also happens. when using inductor and capacitor for impedance transformation there is a possibility of getting voltage higher than supply voltage,.

regards
chethan
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chethan_RFIC
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Re: basic LNA power related doubt
Reply #2 - Apr 26th, 2017, 8:08am
 
this is similar to Transformer concept.
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