Friday, October 15, 2010

#CHIPS: "Triple-mode graphene transistors go analog"

Digital circuitry may be destined to migrate from silicon- to carbon-based, but what about analog? These researchers claim that analog functions can also be enhanced by using the ambipolar nature of carbon-transistors to behave as both n-type and p-type transistors, depending on their bias. Look for carbon analog circuitry to evolve along with digital to replace silicon chip by the end of the decade. R. Colin Johnnson, Kyoto Prize Fellow @ NextGenLog

Triple-mode graphene transistors consist of a conventional metal source (S) and drain (D) with graphene serving as the channel (upper left). For the demonstration, a back gate  was used (upper right). When presented with an alternating current input (V[subscript]AC) the output depends the bias voltage--in-phase if its less that the input minimum (third from bottom), out-of-phase if greater (bottom) or frequency doubled if they are equal (second from bottom).
Here is what EETimes says about analog carbon transistors: Post-silicon era transistors fabricated from sheets of pure carbon—graphene—are pioneering a new paradigm for digital circuitry, but what about analog circuits? Now Rice University researchers have demonstrated analog graphene transistors that can not only amplify like p-type and n-type silicon transistors, but can also exploit the ambipolar ability of graphene in a novel frequency-multiplication mode. The Rice researchers demonstrated how such triple-mode graphene transistors can be used to build simpler phase-shift keying and frequency-shift keying circuitry...
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