Learn Advance MOSFET Circuits Cascode to Diff Amp on LTSpice

Explain the internal structure of n-type d mosfets and e mosfets, including the gate insulator SiO2, drain and source channels, body connection, and symbolic representations.

Explore three symbolic representations of the n-channel e-mosfet: intrinsic structure, current-direction based, and gate bias based, with pmos notes and dmos context.

Analyze the transfer characteristic of an n-channel MOSFET, detailing threshold voltage and channel formation, and show how Vgs controls Id as a voltage-controlled current source.

Explore the drain-source characteristics of NMOS and PMOS transistors, including pinch-off, channel length modulation, and the regions cutoff, ohmic, and saturation, showing how MOSFETs act as amplifiers or switches.

Explore the drain current equation Id and transconductance gm for eMOSFETs, and learn three gm expressions linking Vgs, Vth, and Id.

Derive the AC model of NMOS and PMOS, linking VGS to Id via gm, and review common source, common gate, and common drain configurations with LTSpice simulations.

Explain the common source amplifier: input gate-to-source, output drain-to-source, with a 180-degree phase inversion. Derive the gain as minus gm times Rd||ro and note the high input, low output impedance.

Explore the common source amplifier simulation in LTspice, verifying a voltage gain of about 2.7, an input impedance around 7.5 megohms, and an output impedance near 1.8 kilohms.

Learn the common gate MOSFET amplifier: input between source and gate, output at drain and gate, with zero phase shift and gm·RD gain; note its low input impedance.

Simulate a common gate amplifier in LTSpice to verify a gain around 17.7 with a 5 mV input, and gauge the input and output impedance.

Explore the common drain amplifier with input applied to gate and drain. Output comes from the source; in AC analysis, ground the drain, yielding gain 1 and infinite input impedance.

Simulate a common drain (source follower) amplifier in LTspice, verify input impedance around 112 kiloohms and output impedance near 80 ohms, and explore gain and waveform plots for AC analysis.

Explore the ac analysis of a constant current source with MOSFETs, deriving the small-signal model and showing that VGS becomes zero, leaving RO as the impedance for NMOS and PMOS.

Master numerical analysis of a common-source amplifier with a current-source load in advanced MOSFET circuits from cascode to differential amplifier on LTSpice.

Design and simulate a cs amplifier with a current-source load in LTspice. Verify a gain near -133 with a 1 mv input producing a 133 mv inverted output.

compare a normal common source amplifier with a common source amplifier using a current source load, highlighting the much higher gain achieved in simulation.

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Explore transconductance equations for MOSFETs, deriving two new forms from gm = μn Cox (W/L)(Vgs−Vth) and linking gm to Id, Vgs−Vth, and diode-connected MOS applications.

Short the drain to the gate to form a diode-connected MOS and study its two-terminal, diode-like saturation behavior, including gate-source and drain-source shorts and LTSpice verification.

Simulate a diode-connected NMOS in LTSpice to plot VDS versus ID and confirm the exponential current beyond the 0.4 V threshold, reflecting diode-like behavior.

Raising the width of M1 increases capacitance and drain current, causing VD to drop and the diode-connected MOS to move from saturation to triode, reducing the amplifier gain.

Explore how adding a source resistor rs to a mosfet enhances impedance and stability, pushing a practical current source toward ideal behavior, with vgs = vgg − id rs.

Analyze the output impedance of a common-source amplifier with source degeneration, accounting for finite ro and lambda, using LTSpice simulations.

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Replace RS with a MOSFET biased in saturation to form a cascode stage that raises output impedance and avoids Ohm's law, with M1 cascoded and M2 degenerating.

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Identify current sources and sinks in circuits, highlighting PMOS sourcing from VDD and NMOS sinking to ground, with reference to a differential amplifier.

Explore how to determine transconductance (Gm) for advanced MOSFET circuits, from cascode configurations to differential amplifier implementations on LTSpice.

Compute the output impedance rout of a two-port mosfet amplifier. Short the input Vin and use Vout over Iout to derive rout with gm, R0, and Rd.

Explore finding the gain of a common source amplifier using the shortcut Av = -gm*(Ro // Rd), with gm and Ro // Rd from prior steps for LTSpice MOSFET analysis.

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