MOS Capacitances — Lesson 2

This lesson covers the in-depth understanding of MOS capacitances. It delves non-idealities in the mosfet. It provides a detailed explanation of the different possible capacitors and their evaluation. The lesson further discusses the concept of junction capacitances and their impact on the functioning of the MOSFET. It also introduces the concept of transition frequency and maximum power gain frequency as important figures of merit for the mosfet.

Video Highlights

00:24 - Introduction
19:00 - Impact of contact resistances, gate resistance, and electromagnetic travel time on the mosfet model
26:52 - Transition frequency (fT) and model for the MOSFET
37:18 - Concept of maximum frequency (fmax) and power gain in a mosfet
51:59 - Power gain calculation considering the presence of gate resistance

Key Takeaways

- Moss capacitance and non-idealities in the mosfet play a crucial role in the functioning of CMOS RF integrated circuits.
- Different capacitors in a mosfet, including gate to source, gate to drain, source to body, and drain to body, have different impacts on the circuit's performance.
- Junction capacitance, which is the capacitance between the drain and the body and the source and the body, is an important concept in understanding the functioning of a mosfet.
- The transition frequency (ft) and the frequency at which maximum power gain (f max) is obtained are two important parameters in a mosfet.
- The power gain at the signal frequency ignores the power coming into the mosfet at DC.