Today was an attempt to cover questions that students had sent me over the weekend.
I talked a little about PN junctions (using the analogy of diffusion of sodium and potassium across the cell membrane from last week’s guest lecture to discuss the voltage that is produced by diffusion of holes and electrons across the PN junction). We then covered diodes, photodiodes (and photovoltaic cells), bipolar transistors, and phototransistors. That whole lecture needs to come before the phototransistor lab.
I then talked about class A, B, and C amplifiers: all of which are the same amplifier structure, but with different bias voltages. I described (in rough terms) the efficiency of each circuit and gave an application for a class C amplifier driving a LC resonant load. I then gave a crude bipolar class AB output circuit, as basically two class-B circuits with opposite polarities.
We also discussed (very briefly) brushed DC motors and stepper/brushless motors.
We ended with some redesign of the T-shirt for the course. I’ll be showing them a new draft of the design tomorrow and taking their orders. Once the design is finalized, I’ll put a rendition of it on this blog—though it will not be the original design, since I’m doing this one in SVG using Inkscape, and WordPress.com still doesn’t support svg images.