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What are the pros and cons of a multi-band PA if compared to a wide-band PA?

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Fávero Santos

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Hello, all!

I'm curious on understanding better what are the pros and cons of a wide band PA over a multi band PA.

I mean, if Hai-Feng Wu et al. are capable of designing a PA with 6.5 GHz BW (as reported in their paper "Analysis and design of an ultrabroad band stacked PA in CMOS technology"), why would anyone prefer a multi-band PA over a wide band one?

Many thanks!
 

First thing comes into my mind is Output Power. Wideband==> Gain*BW=1 rule===> Lower gain(Power in case of a PA)

In some PA's I designed, I needed 30dbm Pout, as well as P1db of 33-34dbm, that paper seemed like a driver amplifier more than a PA to me.
 

ktr said:
First thing comes into my mind is Output Power. Wideband==> Gain*BW=1 rule===> Lower gain(Power in case of a PA)

In some PA's I designed, I needed 30dbm Pout, as well as P1db of 33-34dbm, that paper seemed like a driver amplifier more than a PA to me.
Click to expand...

Hi, ktr

Many thanks on replying. Regarding Gain*BW = 1, their PA is nicelly flat (they report a gain flatness of 18.4 dB +- 1.5 dB for the BW) so it just bugs me that I can't see the difference of using their PA in 2.4 and 5 GHz than using a PA that can change the band from 2.4 to 5 GHz... Maybe a mutiband can be more optimized to the working band?

Thanks

Fávero
 

Optimizing a wide-band PA is pretty difficult.( Efficiency,Power Output,Gain,Linearity)
But a narrow-band PA can be optimized easier than wide-band.
And also, a Transmitter-if there is- will generally work at single frequency at a time even it's capable of transmitting multiple frequency.So, it doesn't make sense to occupy whole spectrum for a single frequency.It will also be eventually power consuming system and low efficient.
So, I would prefer a narrow-band PA instead of wide-band one due to those reasons and probably other causes.
 

If you ask about mobile phone power amplifiers, at the silicon level, the multiband PAs actually they are designed to be wideband PAs.
For each band they use different input/output matching networks, but the PA circuit is almost identical whatever is used for 700MHz band or for 1900MHz band. The interstage matching network is designed for wideband.
Today, generally this is the chosen solution of the big PA manufacturers, as Qorvo or Skyworks.
 

BigBoss said:
So, it doesn't make sense to occupy whole spectrum for a single frequency.It will also be eventually power consuming system and low efficient.
Click to expand...

The interstage matching network is designed for wideband.
Today, generally this is the chosen solution of the big PA manufacturers, as Qorvo or Skyworks.
Click to expand...

Agree with both of the statements; one of the applications I see resulting is that u get a fast switch; then match the PA for different bands; then switch to the frequency that you need to transmit at the given time. So, you basically have a wideband PA, with selectable frequency option, and much more efficient than a normal WB. This is also done to prevent transmitting in a huge range; to prevent your receiver antenna from getting saturated(for transciever applications)
 

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