science

LDMOS

LDMOS is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand LDMOS rather than just read about it. In short: 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.

Key takeaways

LDMOS belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect LDMOS to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of LDMOS from memory before moving on to harder problems.

Reference excerpt

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, Diodes Inc, Tower Semiconductor, TSMC, LFoundry, SAMSUNG, GLOBALFOUNDRIES, Vanguard International Semiconductor Corporation, STMicroelectronics, Infineon Technologies, RFMD, NXP Semiconductors (including former Freescale Semiconductor), SMIC, MK Semiconductors, Polyfet and Ampleon.

Photo gallery

Applications

Common applications of LDMOS technology include the following.

Amplifiers — RF power amplifiers, audio power amplifiers, class AB Audio technology — loudspeakers, high-fidelity (hi-fi) equipment, public announcement (PA) systems Mobile devices — mobile phones Mobile networks — base stations and RF amplifiers Pulse applications Radio-frequency (RF) technology — RF engineering (RF engineering), RF power amplifiers Wireless technology — wireless networks and digital networks

RF LDMOS

Common applications of RF LDMOS technology include the following.

See also FET amplifier Power semiconductor device RF CMOS

References

External links Microwave Encyclopedia on LDMOS BCD process including customizable LDMOS

Illustrations

Worked examples

Example 1 — a first encounter with LDMOS

Start with the simplest possible case. Write down what LDMOS claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to LDMOS before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about LDMOS ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of LDMOS

In research: LDMOS appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses LDMOS in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: LDMOS is common in secondary-school and first-year university syllabi. It links to neighbouring topics Electronic design, MOSFETs, Transistor types, so understanding it makes those chapters shorter.
In everyday life: Look for LDMOS outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study LDMOS in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what LDMOS means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain LDMOS out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is LDMOS in simple terms?

Why does LDMOS matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study LDMOS?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on LDMOS.