I think there are some design errors because the waveforms don't seem to be correct to me ...
For instance, choke coil value should be higher than 1.7nH for 2.45GHz.And so on..
The current waveform is absolutely not correct, it should been sinusoidal-like because the drain current does not increase instanteanously..
Check the component values double..
Zopeon, As I know the MIM capacitance in 0.18um TSMC standard design is in femtofarad range, so there is no problem with 0.3pf capacitance. But remember that original class-E components value introduced in literatures are valid for designs for output filters with quality factor more than 10. So for quality factor of 3, you must compute components differently. For it refer to:
Hung-Lung Tu, S.; Toumazou, C.; , "Effect of the loaded quality factor on power efficiency for CMOS class-E RF tuned power amplifiers," Circuits and Systems I: Fundamental Theory and Applications, IEEE Transactions on , vol.46, no.5, pp.628-634, May 1999.
Of course for the low quality factors, you must consider high distortion due to harmonics. The Y1 plot seems to the transistor's current. But as the current through the transistor is the sum of drain-source capacitance(which make a part of parallel capacitance) and the transistor current, it does not give you a good view. So it is better to plot the current through C36 and transistor current, which is sinusoidal.
Peak current through the transistor is 2.84Idc (RF power amplifiers by Kazimierczuk). so the transistor must sustain this current. The only matter with transistor size is the On-state resistance of the transistor, that decreases when the transistor size increases. But how much can the size increase? When you increase the transistor size, the input capacitance of the transistor increase, so you should mind the input power which lower "power added efficiency" (PAE=(Pout-Pin)/Pdc). You should design the circuit and compute load-network components value, and then increase the transistor size and optimize the PAE of your circuit. I attach a photo to show an example of the changes of efficiency and PAE when transistor fingers incrase. The transistor size of RF-MOS transistors of TSMC are limited, so this transistor is not suitable for power application, I guess you may have to choose standard one.
For DC-feed inductance, the fluctuation of the current flowing through it is not negligible comparing to DC value of it, but the average of the current is constant ( for a given DC supply and output power). The fluctuation of the current can not be absolute-zero, since ideal RF choke is not available.
thanks a lot, could you show the vout waveform also, i have doubt in it.
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