LDMOS
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LDMOS (laterally diffused metal oxide semiconductor) transistors are used in RF/microwave power amplifiers. These transistors are fabricated via an epitaxial silicon layer on a more highly doped silicon substrate.
Such silicon-based FETs are widely used in power amplifiers for base-stations where the requirement is for high output power with a corresponding drain to source breakdown voltage usually above 60 volts, but have lower maximum power gain frequency compared to other devices such as GaAs FETs.
Manufacturers of LDMOS devices include TSMC, Infineon Technologies, RFMD, Freescale Semiconductor, NXP Semiconductors and Polyfet.
Single LDMOS devices suffer from relatively poor efficiency when used in 3G and 4G (LTE) networks, due to the higher peak-to-average power of the waveforms used. The efficiency of LDMOS power amplifiers can be boosted using Doherty or Envelope Tracking techniques.
