The Advantages Of MOSFET Over BJT

Since 1948, transistors have been used in electronics. Originally made with germanium, modern transistors use silicon for its higher heat tolerance. Transistors amplify and switch signals. They can be analog or digital. Two prevalent transistors today include Metal-Oxide-Semiconductor Field Effect Transistors (MOSFET) and Bipolar Junction Transistors (BJT). MOSFET offers a number of advantages over BJT.

MOSFET and BJT represent the two main types of transistors used today. Transistors consist of three pins called an emitter, a collector and a base. The base controls the electric current, the collector handles the flow of the base current, and the emitter is where the current flows out. Both MOSFETs and BJTs are generally made from silicon, with a smaller percentage made from gallium arsenide. They can both work as transducers for electrochemical sensors.

A BJT (Bipolar Junction Transistor) combines two junction diodes from either a p-type semiconductor between to n-type semiconductors or a layer of n-type semiconductor between two p-type semiconductors. The BJT is a current-controlled device with a base circuit, essentially a current amplifier. In BJTs, the current travels through the transistor across holes or bonding vacancies with positive polarity and electrons with negative polarity. BJTs are used in many applications including analog and high power circuits. They were the first mass-produced type of transistor.

MOSFET is a type of Field Effect Transistor that is used in digital integrated circuits like microcomputers. The MOSFET is a voltage-controlled device. It has a gate terminal rather than a base, separated from other terminals by oxide film. This oxide layer serves as an insulator. Instead of an emitter and a collector, MOSFET has a source and a drain. MOSFET is notable for its high gate resistance. The gate voltage determines whether the MOSFET turns on or off. Switching time occurs between its on and off modes.

Field Effect Transistors such as MOSFET have been used for decades. They comprise the most commonly used transistors, currently dominating the market for integrated circuits. They are portable, use low power, draw no current and are compatible with silicon processing technology. Their lack of gate current results in high input impedance. One additional major advantage of MOSFET over BJT is that it forms the basis of a circuit with switches of analog signals. These are useful in data acquisition systems and allow several data inputs. Their switching ability between different resistors aids in attenuation ratio, or changing the gain of operational amplifiers. MOSFETs form the basis of semiconductor memory devices such as microprocessors.