Broadband amplifiers are critical elements in contemporary high-bandwidth wired and wireless communication systems. Such amplifiers are typically designed using distributed amplifiers (DAs) that incorporate transmission line theory to obtain a relatively high gain-bandwidth product (fT).
However, the DA-based design is beset with several shortcomings, including high DC power consumption and the need for a larger surface area. Furthermore, achieving high bandwidth in such amplifiers requires the use of transistors offering high fT, but this usually results in higher fabrication costs, since currently existing fabrication technology offers very low yields. In addition, this design is known to reduce reliability of the transistors, and cause 3 dB losses at the input and output terminals due to the need for 50 Ω impedance matching circuits.
Researchers from the University of California have now invented a novel broadband amplifier that claims to overcome all of the above-mentioned challenges, paving the way for a reliable and cost-effective alternative. The new design method offers desirable gain with a large bandwidth and yet consumes low power. Furthermore, it also ensures low reflection coefficients at the input and output terminals, limits the loss in the circuit, and offers good overall reliability. Also, the new design occupies a smaller area and requires lower DC power consumption.
The UCI researchers developed this novel amplifier by combining a three-stage amplifier design and ensured high performance even without a distributed amplifier. The new invention therefore overcomes most of the limitations of conventional designs.
Typically, the reason for low transistor reliability is the need to operate it at high current densities. The new design, however, facilitates operations even at typical current densities, thus reducing stress on the transistors, and consequently improving their working lifetimes. The novel design also dispenses of the need for 50 Ω impedance matching circuits, and thus helps to avoid the 3 dB loss, and yet permits low levels for S11 and S22 over the operating bandwidth. Such incremental design innovations thus facilitate a low-power broadband amplifier capable of providing significantly high gain-bandwidth product without the need for a distributed amplifier design.
This novel broadband amplifier should benefit numerous applications in fibre-optic communications and wireless communication systems. It also holds considerable potential for future millimetre wave communication circuits requiring significant amplification. In particular, the invention could serve as a modulator driver for limiting automatic gain control and could enable good transimpedance amplifiers. Furthermore, the versatile amplifier can be used to work with several frequency bands in general purpose wireless communications and in testing equipment. Besides these, the amplifier can also find great utility in the field of electronic warfare in military communication systems.
For more information contact Patrick Cairns, Frost & Sullivan, +27 (0)18 464 2402, [email protected], www.frost.com
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