CMOS Inverter Model Using Light Switches 

The NMOS transistor operates very much like a household light switch. Flipping the lever up connects the two switch terminals, which is like applying a positive voltage to the NMOS gate. Conversely, flipping the lever down disconnects the switch terminals, which is like applying 0 volts to the gate.
Turn the switch upside-down, and you have a PMOS transistor model. Flipping the lever down connects the two switch terminals, whereas flipping the switch up disconnects the terminals.
Note: I'm finished using my CMOS inverter and NOR cardboard models. I'm ready to donate them to any teacher who wants them. Leave a comment if you're interested.
Previous video: CMOS Tech: NMOS and PMOS Transistors in CMOS Inverter
• CMOS Tech: NMOS and PM...
The CMOS inverter uses a PMOS transistor and an NMOS transistor with the source terminals connected to the power supply and ground, respectively, and the drains connected together to make the output and the gates together to make the input. You can build a model of the inverter as shown in the video.
When you tie the two transistor gates together, the model shows how the single input turns on one transistor while turning off the other. This ensures that there is never a conducting path from power supply to ground, which would quickly drain the battery and generate a lot of heat from the high current.
Furthermore, it ensures that the output is always connected to either the power supply or ground, and never allowed to float. A floating output would result in an unknown intermediate voltage a the input of logic device downstream. This could cause both the PMOS and NMOS of transistors to be partially turned on, providing a short-circuit path from power to ground in the downstream device.
The next video shows a light-switch model for a slightly more complicated circuit that performs the logical NOR function.
CMOS NOR Logic Model Using Light Switches
• CMOS NOR Logic Model U...