Power Amplifier tradeoff between output power and voltage swing

Could anyone explain why transistors with an ft of 200GHz dictate a voltage swing of less than 1V ?

The reference [3] can be found here which I am having hard time reading it now

promach said:

Could anyone explain why transistors with an ft of 200GHz dictate a voltage swing of less than 1V ?

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You do not need to read the whole article, just read the section II, 1st paragraph.

ft*BreakdownVoltage=200GHz*V for silicon <=> BreakdownVoltage of silicon=200GHz*V/ft

A silicon transistor with ft=200GHz has 1V breakdown. Just use the math.

Power Amplifiers drive the Loads as either Current Source or Voltage Source or both depending on the Load Impedance.
If the Load Impedance is low, the Voltage Swing will be smaller but Current Swing will be higher, if the Load Impedance high, the Voltage Swing will be larger, the Current Swing will be in this case smaller ..
So on..
There is a very good project file and video at Youtube by Keysight Technologies.If you're able to reach ADS, you can study with this nice example project on Power Amplifiers.Recommended..
It explains what happens ina Power Amplifier by classification.

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CataM said:

ft*BreakdownVoltage=200GHz*V for silicon <=> BreakdownVoltage of silicon=200GHz*V/ft
A silicon transistor with ft=200GHz has 1V breakdown. Just use the math.

Click to expand...

I don't agree with this statement.There are some SiGe foundries and their BJT HBT transistors work over 4V.( fTs are around 150-300GHz )
There should be some additional information to make it true..fT has some relationships with intrinsic caps and especially intrinsic base resistance and emitter resistance ( it's valid for MOSs too)
but breakdown voltage shouldn't be-at least particularly- a parameter over fT of a transistor.

For those who are interested in power amplifier, https://www.keysight.com/upload/cmc_upload/All/PA_Design_Series.htm

However, I do not have access to the software ADS though

By the way, there is also IEEE magazine series ("A Technical Foundation for RF CMOS Power Amplifiers" split into 6 parts) on power amplifier. The first part can be found at https://ieeexplore.ieee.org/document/7258473 . Google the rest of the 6 parts.