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Low-Voltage Power Electronics
Published in John D. Cressler, H. Alan Mantooth, Extreme Environment Electronics, 2017
Mohammad Mojarradi, Philippe Adell
Compared to VDMOS transistor, CMOS-compatible high-voltage transistors (also known as LDMOSFETS) are not self-aligned and have much lower current handling capacity. At the same time, these transistors enable the construction of high-voltage interface circuits in the same substrate as the low-voltage controllers. The use of LDMOS transistors in CMOS processes to enable development of low-voltage power circuits are summarized in Table 60.1. LDMOS transistors enable the traditional CMOS process to fabricate the controller and the pre-driver sections of a power electronics circuit in the same integrated circuit. Also, given similar characteristics, when it comes to operate at low temperature, LDMOS are more rad-tolerant compared to vertical DMOS devices due to their device structures and reduced oxide thickness.
Semiconductors in Mobile Telecommunications
Published in Saad Z. Asif, 5G Mobile Communications Concepts and Technologies, 2018
GaN has power densities four to five times greater than silicon embedded LDMOS (Laterally Diffused MOSFET). Thus, with these power levels, GaN HEMT (High-Electron-Mobility Transistor) device capacitances are also much lower, providing the ability to increase instantaneous bandwidths without losing efficiency which is the key for LTE/4G and future 5G systems. LDMOS on the other hand is still the key device for RF power amplifiers in base stations of wireless communications systems. Additionally, GaN-on-SiC, which is the mainstay of GaN technology, is effective for remote radio heads, multi-standard and multi-frequency base stations, pico and femto cells, and for larger bandwidths where Si LDMOSFETs are not suitable [9,12].
Power Amplifier Circuit
Published in Mike Golio, Commercial Wireless Circuits and Components Handbook, 2018
LDMOS is a very cheap silicon process that allows MOS devices to be integrated with passives onto a die. LDMOS uses a slow, well-controlled, and repeatable lateral diffusion process to effectively make the device gate much smaller than its drawn dimension. Since (to a first order) performance is inversely proportional to gate length, LDMOS offers very good RF and microwave performance. However, performance is currently limited to around 3 GHz as an upper maximum.
Cost-Optimized Energy-efficient Power Amplifier for TD-LTE Outdoor Pico Base Station
Published in IETE Journal of Research, 2022
Brijesh Shah, Gaurav Dalwadi, Hardip Shah, Nikhil Kothari
Although the efficiency enhancement techniques for macro BS discussed in Section 2 can be extended to small cells such as femto and outdoor pico, their applications are restricted due to certain drawbacks. (1) LDMOS transistors are used for the macro BS design with good power efficiency for high-power application. LDMOS transistors are not available with high-power efficiency for less than 10 W continuous wave (CW) power which is required for outdoor pico BS. (2) Additional –48 V to 28 V DC–DC converter is needed to provide the external interface of −48 V DC as per the standard telecom usage. The converter increases the power consumption of BS as well as the bill of material (BoM). (3) Either a copper plate or bulky heat sink is required to dissipate the heat of LDMOS transistor also adds to BoM and fabrication cost. (4) Because of process variations during manufacturing of LDMOS transistors, programmable control of gate bias and tuning in mass production becomes necessary which further increase BoM and process cost. (5) Doherty PA along with DPD demands additional down-converter chain and FPGA or DSP device for algorithm implementation [13]. This, in turn, increases power consumption and defeats power saving by Doherty design in small cell and outdoor pico BS application.