Editing Monolithic microwave integrated circuit

{{Short description|A type of integrated circuit (IC) device that operates at microwave frequencies}}
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[[Image:MMIC example.jpg|thumb|right|300px|Photograph of a GaAs MMIC (a 2–18 GHz upconverter)]]
[[Image:Monolithic microwave integrated circuit MSA0686 fixed.png|thumb|MMIC MSA-0686.]]
'''Monolithic microwave integrated circuit''', or '''MMIC''' (sometimes pronounced "mimic"), is a type of integrated circuit (IC) device that operates at [[microwave]] [[radio frequency|frequencies]] (300&nbsp;MHz to 300&nbsp;GHz). These devices typically perform functions such as microwave [[Frequency mixer|mixing]], power amplification, [[Low-noise amplifier|low-noise amplification]], and high-frequency switching. Inputs and outputs on MMIC devices are frequently matched to a [[characteristic impedance]] of 50 ohms. This makes them easier to use, as cascading of MMICs does not then require an external [[matching network]]. Additionally, most microwave test equipment is designed to operate in a 50-ohm environment.

MMICs are dimensionally small (from around 1&nbsp;mm<sup>2</sup> to 10&nbsp;mm<sup>2</sup>) and can be mass-produced, which has allowed the proliferation of high-frequency devices such as [[cellular phone]]s. MMICs were originally fabricated using [[gallium(III) arsenide|gallium arsenide]] (GaAs), a [[Extrinsic semiconductor#Semiconductor doping|III-V compound semiconductor]]. It has two fundamental advantages over [[silicon]] (Si), the traditional material for IC realisation: device ([[transistor]]) speed and a semi-insulating [[Wafer (electronics)|substrate]]. Both factors help with the design of high-frequency circuit functions. However, the speed of Si-based technologies has gradually increased as transistor feature sizes have reduced, and MMICs can now also be fabricated in Si technology. The primary advantage of Si technology is its lower fabrication cost compared with GaAs. Silicon wafer diameters are larger (typically 8" to 12" compared with 4" to 8" for GaAs) and the wafer costs are lower, contributing to a less expensive IC.

Originally, MMICs used [[MESFET|metal-semiconductor field-effect transistors]] (MESFETs) as the active device. More recently [[high-electron-mobility transistor]] (HEMTs), pseudomorphic HEMTs and [[heterojunction bipolar transistor]]s have become common.

Other III-V technologies, such as [[indium phosphide]] (InP), have been shown to offer superior performance to GaAs in terms of gain, higher cutoff frequency, and low noise. However, they also tend to be more expensive due to smaller wafer sizes and increased material fragility.

[[SiGe|Silicon germanium]] (SiGe) is a Si-based compound semiconductor technology offering higher-speed transistors than conventional Si devices but with similar cost advantages.

[[GaN|Gallium nitride]] (GaN) is also an option for MMICs.<ref name=at-2016-radar>{{Cite web|url=https://arstechnica.com/information-technology/2016/06/cheaper-better-faster-stronger-ars-meets-the-latest-military-bred-chip/|title=A reprieve for Moore's Law: milspec chip writes computing's next chapter|website=Ars Technica|access-date=2016-06-14|date=2016-06-09}}</ref> Because GaN transistors can operate at much higher temperatures and work at much higher voltages than GaAs transistors, they make ideal power amplifiers at microwave frequencies.

==See also==
* [[Hybrid integrated circuit]]
* [[Transmission line]]

==References==
* ''Practical MMIC Design'', Steve Marsh, published by Artech House {{ISBN|1-59693-036-5}}
* ''RFIC and MMIC Design and Technology'', editors I. D. Robertson and S. Lucyszyn, published by the IEE (London) {{ISBN|0-85296-786-1}}
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[[Category:Integrated circuits]]
[[Category:Microwave technology]]