Almost all analog electronics, from cassette players to the radio parts of mobile phones, are based around transistor amplifiers. These are circuits based on transistors which will take an input signal and amplify the voltage or the current to produce a much larger output.
(c) Benedikt Seidl" alt="Transistors in different housings" />There are 2 main types of amplifier: Positive gain, where if you increase the input you increase the output; and negative gain, where if you increase the input the output decreases. These both involve different physical types of transistor, so if you want an amplifier to do both the circuit you need gets much more complex.
Xuebei Yang and colleagues from Rice University in Houston has been working on transistors made form graphene, the promising material that consists of a single layer of carbon. The transistors they have built change their behaviour entirely depending on the bias voltage you apply to them, changing from positive gain to negative gain, through an intermediate frequency doubling state.
This could make simple amplifiers slightly more flexible but they say that it could have a much bigger effect on transmitters that encode the signal in the frequency or the phase of the signal, plus whatever the very innovative electronic engineers can come up with. Ultimately, this technology could lead to smaller, cheaper and possibly more power efficient mobile phones and other radio devices. Also, as graphene has very good high frequency properties, they could work a lot faster than the present ones!