10.3.2. Differences Between MOSFET and BJT

Whereas, for BJT the instead of applying directly voltage we may say it is a combination of voltage and current. And, in fact, it controls the current in the output port by applying current to the controlling port. So, that is a basic difference of MOSFET with respect to bipolar junction transistor.

This chunk highlights the fundamental difference between MOSFETs and BJTs (Bipolar Junction Transistors). In BJTs, both voltage and current are used for control; specifically, a small input current at the base terminal controls a larger output current flowing from collector to emitter. In contrast, MOSFETs rely primarily on voltage to control the current, meaning that a change in the gate voltage alters the conductivity of the channel, allowing or blocking the flow of current between the drain and source terminals without requiring additional current.

Think of a BJT like a water faucet where turning it on requires both a lever (current) and pressure (voltage) to control the flow of water (current). In comparison, a MOSFET behaves more like a valve that only needs pressure (voltage) to open and close, making it simpler and often more efficient in circuits.

In fact, MOSFET it offers many advantages for realizing the digital circuit. As a result, as the digital with progress of time as the digital portion of the whole system it is dominating.

This chunk discusses the advantages of MOSFETs in the context of digital circuits. MOSFETs are favored in digital applications because they can be easily miniaturized, operate at higher speeds, and consume less power compared to BJTs. As technology has evolved, the demand for digital devices has increased. This trend has led to the widespread adoption of MOSFETs in integrated circuits (ICs), especially for digital processing, highlighting how the landscape of electronic components has shifted toward favoring MOSFET technology for modern applications.

Imagine comparing an efficient electric car (MOSFET) to a traditional gasoline car (BJT). The electric car is simpler, quieter, and often more efficient, representing how the MOSFET fits the growing demand for compact and efficient digital devices, similar to how electric vehicles are becoming more popular in a world that values lower emissions and efficiency.

However, in last say 2 decades in fact, it may be more than that, the analog and digital counterpart of a system they are getting integrated together within single IC.

This section talks about the trend over the past couple of decades where both analog and digital circuits have started being integrated into single ICs. This integration means that technologies initially designed separately for analog and digital applications need to work together. It highlights the need for devices like MOSFETs that can handle both analog and digital functionalities, making them versatile for modern applications that require seamless interaction between various electronic functions on a single chip.

Consider a smartphone as an example of integration. Just like how a smartphone combines a camera, GPS, and many other features into one device, modern ICs combine analog and digital functions using MOSFETs. This integration allows devices to be more compact and multifunctional, just as a smartphone is more convenient than carrying several separate devices.

So, when you say n-type it refers to the type of the channel would be created. Of course, originally it was p-type, but after applying the voltage here the channel it is getting converted into n-type.

In this chunk, the differences regarding substrate types for the two devices are discussed. For n-MOSFETs, the substrate starts as p-type and becomes n-type when a voltage is applied, forming a channel for current flow. This is significant because it affects how each device operates within a circuit. Understanding whether you're dealing with n-type or p-type materials can influence circuit design decisions in electronics.

Think of a n-MOSFET as a transformer. Initially, it is set for one type of operation (p-type), but when a certain voltage is applied, it converts and adapts to another operational mode (n-type). Just like a transformer can switch between different voltages, the n-MOSFET switches its channel type, allowing it to perform different roles in a circuit depending on the input signal.

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