LDMOS (laterally-diffused metal-oxide semiconductor) is a planar double-diffused MOSFET (metal–oxide–semiconductor field-effect transistor) used in amplifiers, including microwave power amplifiers, RF power amplifiers and audio power amplifiers. These transistors are often fabricated on p/p+ silicon epitaxial layers. The fabrication of LDMOS devices mostly involves various ion-implantation and subsequent annealing cycles. As an example, The drift region of this power MOSFET is fabricated using up to three ion implantation sequences in order to achieve the appropriate doping profile needed to withstand high electric fields.
The silicon-based RF LDMOS (radio-frequency LDMOS) is the most widely used RF power amplifier in mobile networks, enabling the majority of the world's cellular voice and data traffic. LDMOS devices are widely used in RF power amplifiers for base-stations as the requirement is for high output power with a corresponding drain to source breakdown voltage usually above 60 volts. Compared to other devices such as GaAs FETs they show a lower maximum power gain frequency.
Manufacturers of LDMOS devices and foundries offering LDMOS technologies include TSMC, LFoundry, Tower Semiconductor, GLOBALFOUNDRIES, Vanguard International Semiconductor Corporation, STMicroelectronics, Infineon Technologies, RFMD, Freescale Semiconductor, NXP Semiconductors, SMIC, MK Semiconductors, Polyfet and Ampleon.
The invention of the metal–oxide–semiconductor field-effect transistor (MOSFET) by Mohamed M. Atalla and Dawon Kahng at Bell Labs in 1959 was a breakthrough in power electronics. Generations of power MOSFETs enabled power designers to achieve performance and density levels not possible with bipolar transistors. In 1969, the DMOS (double-diffused MOSFET) with self-aligned gate was first reported by Y. Tarui, Y. Hayashi and Toshihiro Sekigawa of the Electrotechnical Laboratory (ETL).
In 1977, Hitachi introduced the LDMOS, a planar type of DMOS. Hitachi was the only LDMOS manufacturer between 1977 and 1983, during which time LDMOS was used in audio power amplifiers from manufacturers such as HH Electronics (V-series) and Ashly Audio, and were used for music, high-fidelity (hi-fi) equipment and public address systems.
In the early 1990s, RF LDMOS (radio-frequency LDMOS) was introduced, as RF power amplifiers for cellular network infrastructure. They eventually displaced RF bipolar transistors, because RF LDMOS provided superior linearity, efficiency and gain along with lower costs. With the introduction of the 2G digital mobile network, LDMOS became the most widely used RF power amplifier technology in 2G and then 3G mobile networks. By the late 1990s, the RF LDMOS had become the dominant RF power amplifier in markets such as cellular base stations, broadcasting, radar, and Industrial, Scientific and Medical band applications. LDMOS has since enabled the majority of the world's cellular voice and data traffic.
In the mid-2000s, RF power amplifiers based on single LDMOS devices suffered from relatively low efficiency when used in 3G and 4G (LTE) networks, due to the higher peak-to-average power of the modulation schemes and CDMA and OFDMA access techniques used in these communication systems. In 2006, the efficiency of LDMOS power amplifiers was boosted using typical efficiency enhancement techniques, such as Doherty topologies or envelope tracking.
As of 2011[update], RF LDMOS is the dominant device technology used in high-power RF power amplifier applications for frequencies ranging from 1 MHz to over 3.5 GHz, and is the dominant RF power device technology for cellular infrastructure. As of 2012[update], RF LDMOS is the leading technology for a wide range of RF power applications. As of 2018[update], LDMOS is the de facto standard for power amplifiers in mobile networks such as 4G and 5G.
Common applications of LDMOS technology include the following.
- Amplifiers, including RF power amplifiers, audio power amplifiers, and Class AB.
- Audio technology, including loudspeakers, high-fidelity (hi-fi) equipment, and public announcement (PA) systems.
- Mobile devices, such as mobile phones.
- Mobile networks, including base stations and RF amplifiers.
- Pulse applications.
- Radio-frequency (RF) technology, including RF engineering (RF engineering) and RF power amplifiers.
- Wireless technology, including wireless networks and digital networks.
Common applications of RF LDMOS technology include the following.
- Aerospace and defense technology, including military applications.
- Automatic dependent surveillance – broadcast (ADS–B).
- Avionics, including ADS-B transponders, identification friend or foe (IFF) transponders, secondary surveillance radar (SSR), distance measuring equipment (DME), Mode S edge-localized mode (ELM), and tactical data link (TDL).
- Broadcasting, including television (TV) and FM broadcasting.
- Cellular networks, including 2G, 3G, Long-Term Evolution (LTE), 4G, 5G, and 5G New Radio (5G NR).
- Electronic warfare, including communications information warfare and multi-band communication systems.
- Cellular voice and data traffic.
- Heating, including RF heating and microwave heating.
- High frequency (HF) communication, including very high frequency (VHF) and ultra high frequency (UHF).
- Industrial, Scientific and Medical band (ISM band).
- Laser drivers.
- Medical technology, such as magnetic resonance imaging (MRI).
- Millimeter-wave (mmW) technology.
- Mobile radio, including professional mobile radio, mobile broadband, handheld transistor radio, analog and digital radio, and Terrestrial Trunked Radio (TETRA).
- Particle accelerators.
- Pulse applications.
- Radar technology, including HF, UHF, VHF, L band, S band, wideband, and narrowband.
- Radio technology, including commercial radio, public safety radio, and marine radio.
- Radio-frequency (RF) technology, including radio-frequency identification (RFID) and RF plasma generators.
- RF energy technology, including lighting, medical technology, drying, and automotive electronics.
- Kitchen appliances, including smart appliances, countertop appliances, cooking appliances, RF cooking, microwave cooking, RF defrosting, frozen food defrosting, freezers, refrigerators, and ovens.
- Smart lighting, including RF lighting and wireless light switch.
- Voltage standing wave ratio (VSWR).
- Wideband and mobile communications, including base stations, military communications, emergency position-indicating radiobeacon station (EPIRB), sonar buoys, and automatic meter reading (AMR).
- Wireless technology, including mobile communication, satellite communication, wireless data modems, and WiMAX.
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