MOSFET Amplifier, LDMOS Amplifier, CMOS Amplifier & FET Amplifier

About MOSFET

Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET, MOS FET, or MOS-FET), also called the metal-oxide-silicon transistor (MOS transistor or MOS), is a type of insulated-gate field-effect transistor, which is fabricated by the controlled oxidation of a semiconductor (usually silicon).

The voltage of the covered gate determines the electrical conductivity of the device. This ability to change conductivity with the amount of applied voltage can be used for amplifying or switching electronic signals.

By the mid-1960s, RCA was using MOSFETs in their consumer products like amplifiers, FM radios, as well as televisions. In 1967, researchers Donald Klein, John Sarace, and Robert Kerwin from Bell Labs developed the self-aligned gate (silicon-gate) MOS transistor and researchers Tom Klein & Federico Faggin from Fairchild adapted that kind of transistor for integrated circuits in 1968.

MOSFET Power Amplifier

Power MOSFET is a specific kind of MOSFET designed to handle significant power levels. It has some advantages over the other power semiconductor devices like a thyristor or an insulated-gate bipolar transistor (IGBT). Power MOSFET has good efficiency and high switching speed at low voltages.

Power MOSFET shares an isolated gate with the IGBT. So, it is easy to drive the isolated gate. Both power MOSFET and IGBT can be subject to low gain, sometimes to a degree that the gate voltage needs to be higher than the voltage under control.

Tohoku University and Jun-ichi Nishizawa invented a power MOSFET for audio in 1974. This audio power MOSFET was soon manufactured by Yamaha Corporation for their high-fidelity audio amplifiers. Also, in 1974, Sony, JVC, and Pioneer Corporation began manufacturing amplifiers with power MOSFETs.

Power MOSFETs with lateral structure (e.g. LDMOS) are mainly used in high-end audio amplifiers and high-power PA systems.

LDMOS Amplifier

LDMOS, Laterally-Diffused Metal-Oxide-Semiconductor, is a planar double-diffused MOSFET that is applied in amplifier, including RF (radio-frequency) power amplifier, audio power amplifier, and microwave power amplifier.

The silicon-based RF LDMOS is the most widely used RF power amplifier in mobile networks. It enables 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 typically above 60 volts.

CMOS Amplifier

Complementary Metal–Oxide–Semiconductor (CMOS) amplifiers are ubiquitous analog circuits in computers, cellphones, cameras, biomedical circuits, audio systems, telecommunication systems, as well as many other systems.

CMOS amplifiers’ performance influences the whole specifications of the systems. They make use of MOSFETs. CMOS amplifiers are simpler to fabricate and therefore less expensive than bipolar junction transistors (BJT) amplifiers.

CMOS amplifiers offer a sufficiently high transconductance to enable the design of very high-performance circuits. In high-performance CMOS amplifier circuits, transistors are used to amplify the signal. Also, they are used as active loads to achieve higher gain and output compared with resistive loads.

FET Amplifier

A FET amplifier is an amplifier that makes use of one or more field-effect transistors (FETs). The most common kind of FET amplifier is the MOSFET amplifier that uses MOSFETs. Using FET for amplification gets high input impedance while low output impedance.

FET Amplifiers Types

• Common gate amplifier: The gate is common to both input and output.
• Common source amplifier: The source is common to both input and output.
• Common drain amplifier: The drain is common to both input and output. It is also called a source follower.