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richie, generating 100VAC at a frequency of 100~1000 MHz requires a huge amount of power to overcome the stray capacitance. Even just one picofarad of stray capacitance has a reactance of 160 ohms at 1 GHz so you will waste 625 watts of power for every picofarad of stray capacitance at 100V RMS! In other words, it's not really practical. What do you want to do with this voltage?
Do you have a specific piezoelectric crystal in mind? Can you link to a data sheet?
Piezoelectric transducers have significant capacitance. Calculate the amount of energy required to make 50Vp-p at 100 MHz appear across even just 1nF of capacitance:
V=50/2/sqrt(2) = 17.7V.
Xc = 1/(2 pi f C) = 1/(2 pi 1e8 1e-9) = 1/(0.2 pi) = 1.6 ohms
P=V^2/R = 17.7^2 / 1.6 = 200W.
What kind of "waves" are you talking about? If you're talking about physical motion, the only things that have low enough mass for you to move them any significant distance at 100 MHz will be electrons, I think!
OK, I'm way out of my depth talking about lithium niobate.
Are you serious about making things physically vibrate at 100 MHz?
I think if you only want 1W dissipation, you'll have to reduce the voltage a lot. Do you have a figure for the capacitance between the electrodes? I assume you will be attaching electrodes to a piece of this stuff?
You should be able to calculate the voltage you'll need using the formulas in my previous post. Once you know the capacitance, you can calculate the reactance at your desired frequency, and from that, and the power dissipation you want, you can calculate the voltage you will need.
I would imagine a radio transmitter might be a good place to start. It's not too hard to generate 1W at 100 MHz at a relatively low voltage. Do a google search.
Describing what you want using simple terms doesn't magically make it simpler to make! When you're dealing with high frequencies and significant power, simple electronic design principles don't apply, and special techniques are needed to make something that will actually work.... basically just something to take the DC -> AC, and amplify a little.