Usage of MOSFET over BJTs in intergrated circuits

MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) are widely used in integrated circuits (ICs) for several reasons:

• Power Efficiency: MOSFETs have a high input impedance, which means they require very little input current to control the device. This results in low power consumption and higher efficiency compared to BJTs (Bipolar Junction Transistors), which require a significant base current to operate.
• Size and Density: MOSFETs can be fabricated in a much smaller size compared to BJTs, allowing for higher-density integration on a chip. This is because the fabrication process for MOSFETs is compatible with complementary metal-oxide-semiconductor (CMOS) technology, which is widely used in IC manufacturing. CMOS technology allows for the integration of both NMOS (n-channel MOSFETs) and PMOS (p-channel MOSFETs) on the same chip, enabling complex circuit designs.
• Noise Immunity: MOSFETs have a high input impedance, which makes them less susceptible to noise compared to BJTs. This is particularly important in integrated circuits, where the close proximity of various circuit components can lead to signal interference. The high input impedance of MOSFETs helps to minimize the impact of such interference.
• Manufacturing Compatibility: MOSFETs are compatible with the standard CMOS manufacturing process, which is widely used in the semiconductor industry. This compatibility allows for the integration of other CMOS components, such as logic gates, memory cells, and other complex circuits, on the same chip, simplifying the manufacturing process and reducing costs.
• Switching Speed: MOSFETs have a faster switching speed compared to BJTs. This is advantageous for high-frequency applications and digital circuits where fast switching is required.

While BJTs still have their applications, such as in analog circuits and certain specialized applications, the advantages of MOSFETs, particularly in terms of power efficiency, size, noise immunity, and manufacturing compatibility, have made them the dominant choice in modern integrated circuits.

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