Simulation of Enhancement MOSFET

This lecture by Vincent Chang demonstrates the simulation of an N-channel enhancement MOSFET using SPICE. The instructor begins by introducing the device structure and circuit symbol, explaining the four terminals (source, gate, drain, body) and the key voltages VGS and VDS. He then describes the output characteristic (ID vs VDS) and the transfer characteristic (ID vs VGS), highlighting the triode and saturation regions and the boundary between them. The simulation process is shown step-by-step, including the SPICE input files for both characteristics. The output characteristic is simulated by sweeping VDS from 0 to 10V for different VGS values (1-5V), producing a family of curves. The transfer characteristic is simulated by fixing VDS at 6V and sweeping VGS from 0 to 12V. The instructor points out an interesting observation: the transfer characteristic is a parabola for low VGS but becomes a straight line for higher VGS. He explains that this occurs because the device transitions from saturation to triode region as VGS increases, changing the governing equation from square-law to linear. The lecture emphasizes the importance of reconciling simulation results with hand analysis to understand the underlying physics.