What causes poor performance in CMOS power amplifier?

i am also having the same question.Albeit MOS devices are high frequency of operation upto X band having V as well as I gain but we are seldom using it as a power amplifier. what is reason behind that?

CMOS process is cheaper comparable with others (GaAs, SiGe, etc). A CMOS PA can meet in some limits the same performances with competitors.
Nobody wants to make a CMOS PA with poor performance. Just cheaper.

Hi vfone,
Thanks for reply, but we guys desire to know what the physical reasons or
parameters of CMOS to prevent itself from being a good PA.

I think the limitations of CMOS technology such as low device breakdown voltage introduce additional challenges for CMOS PA realization.

Here is one doc talks in detail on the PA design using CMOS process
http://kabuki.eecs.berkeley.edu/~rsn...s/qualprop.pdf

.....manju....

CMOS power amplifier?s performance is limited because of its low breakdown voltage, low current drive, and lossy substrate.
If you are thinking to CMOS PA?s for mobile radios, Silicon Labs already have a product like this on the market (Si4300). Are a few start-ups located in California that soon will have also. I am pretty sure that will be a growing market for this kind of stuff.

Here are some issues designing a CMOS PA:
http://bwrc.eecs.berkeley.edu/Presen...ayanaswami.pdf

The main problem in the past was the working frequency of CMOS technology but in recent years and with decreasing channel length designers can reach to GHz frequenceis. In low power circuits like handsets and ... it used more and more. In high power applications there were slower development in replacement with cheaper cmos.
The most challenging thing in near future is the tradeoff between linearity and efficiency with using cheaper solution. This is becuase of using non-constant envelope modulations in 3G and 4G.

Hi Guys:

In addition to the inquiry, How feasible is CMOS PA to be integrated with the front end modulation and preamplifier stage in 5GHz application?. What are the issue should be look upon?. Thanks in advance

Rgds

For non constant envelop system,CMOS PA still has the problem with linearity.And the coupling through the substrate will be a problem for integration.

there are two main issues in the design of power amplifiers in submicron CMOS,oxide breakdown and hot carrier effect.Both of this get worse as the technology scales.The oxide breakdown is a catastrophic effect and sets a limit on the maximum signal swing on drain .the hot carrier effect, is a reliability issue.It increases the threshod voltage and consequently degraeds the performance of the device.

<A 2.4-GHz 0.18-m CMOS Self-Biased Cascode Power Amplifier>
Tirdad Sowlati, Member, IEEE, and Domine M. W. Leenaerts, Senior Member, IEEE