why do we need power amplifier driver (PAD) in modern transmitter?
I am wondering why it is very common to have a power amplifier driver(PAD) in modern transmitter? WHat is the reason of it? to improve efficiency? or to get better linearity?
Thanks
In order to get enough gain.
The final amplifier stage (output stage) is not enough to amplify the signal to target power.
Well, I guess it makes sense.
then what is the difference between the PAD and PA?
what is the efficiency of PAD? I will guess it is less efficient. Then how much power it will burn compared with PA?
Thanks
PAD has less OIP3 and P1dB.
No, the PAD maybe has hogher effiency than PA because of the less power consumption.
See the datasheet.
Hi tony
So the PAD can consume less power, it is just to amplifier the signal. While the PA needs to concerns more about the efficiency, right?
Can you provide a sample data sheet?
Thanks
The efficiency of each stage is independent, and comes down to what signals you are passing through the system and how you plan to organize your amplification chain, based on the type of signal you are amplifying (PAR, bandwidth, broadband noise level requirements, etc). You could have a very linear driver (which has a poor efficiency) and a highly compressed final amp stage (high efficiency), or vice-versa... it all depends on what your system is trying to accomplish with a given type of signal.
PADs are simply additional amplifier stages.... and amplifier is an amplifier is an amplifier. You can optimize them to run in different classes of operation, or operate with low noise figure, maximum gain, maximum output power, etc. There are many ways to tweak them, but it all comes down to what your signal power from the exciter (modem) is, and what your required output power and signal performance specs look like at the antenna port. You may need 4 gain stages (including the finals) to get up to the power level you need... therefore you'd have three "driver" stages and one "final" amplifier stage, but again... they're all just amplifiers, optimized to perform their specific job, and in concert, get the signal from point A to point B with the proper amount of gain and acceptable distortion/noise.
I see. Thank you for the clear explaination. As you can may can see, I did not have real power amplifier experience.
Thanks a lot