It is not even the fastest. This article did well to leave out actually fast transistors, only comparing to graphene transistors which most people don't really consider fast in the first place.

Checkout Indium Phosphide HEMTs (High electron mobility transistors): http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=4419013

Mark Rodwell's group in UCSB (http://www.ece.ucsb.edu/Faculty/rodwell/rodwell_info/rodwell...) has been working on these transistors for a while. I think they're pushing 2 THz currently.

drive a periodic waveform and sample repeatedly. Assuming you don't somehow sample the same point in the periodic waveform each time, you'll eventually get the complete waveform.

> Assuming you don't somehow sample the same point in the periodic waveform each time, you'll eventually get the complete waveform.

To add an example of a real technique: You can use a short laser pulse and change the time-of-flight (mirrored path on a stepper motor, for instance). This technique will get you to the terahertz region, which is pretty much state of the art for where electronic devices still have gain.

http://en.wikipedia.org/wiki/Terahertz_time-domain_spectrosc...