Voltage amplifier
A voltage amplifier device capable of amplifying small alternating voltage signals. The voltage amplifier is the main building block in analogue electronics. Amplification or voltage gain must be larger than 1 if the device is to be called an amplifier.
Graphene
Graphene is an allotrope of carbon, whose structure is one-atom-thick planar sheets and is most easily visualized as an atomic-scale chicken wire made of carbon atoms and their bonds. The crystalline or "flake" form of graphite consists of many graphene sheets stacked together. Graphene differs from most conventional three-dimensional materials. Intrinsic graphene is a semi-metal or zero-gap semiconductor and has remarkably high electron mobility at room temperature.
Graphene exhibits a minimum conductivity which is still unclear. However, rippling of the graphene sheet or ionized impurities in the SiO2 substrate may lead to local puddles of carriers that allow conduction. Graphene has the ideal properties to be an excellent component of integrated circuits. Graphene has a high carrier mobility, as well as low noise, allowing it to be used as the channel in a FET. The issue is that single sheets of graphene are hard to produce, and even harder to make on top of an appropriate substrate. But many scientists believe that it cannot compete with silicon in applications requiring voltage amplification, like analogue amplifiers and digital logic gates.
Graphene amplifier
A triple-mode single-transistor graphene amplifier was made by researchers of University of California, Riverside and Rice University capable of amplification of 0.02 which was only an attenuator and not an amplifier.
There was only one previous report of voltage amplification in a graphene device, which itself proved difficult to fabricate. The device was not integrated either and so required external metal inductors and capacitors to operate. Moreover, the voltage gain achieved was not large enough for general use. Also it is no easy task to obtain signal amplification in graphene devices.
Without voltage amplification though, graphene electronic devices will be mostly limited to high-frequency (more than 100 GHz) analogue mixers. As analogue electronics cannot exist without voltage amplifiers, graphene devices would need to be integrated with silicon transistors for this most important task of signal amplification
The first graphene device capable of significant voltage amplification (more than 10 dB) which could compete head-on with silicon as the material of choice in electronics has been fabricated by researchers in Italy.
According to researchers, even though it is their first graphene amplifier, it already shows a remarkable performance with a flat frequency response well exceeding the audio range (more than 20 kHz) and a very low total harmonic distortion (less than 1%).
Researchers believe that graphene should not just be confined to specialist, low-voltage gain, and high-frequency applications but can challenge silicon head-on in voltage amplification. They also feel that amplification of audio signals in audio voltage amplifiers which are the main components of home-theatres and iPods, for example, could now be possible using graphene.