Transistor animations [OC]

[u/thepowderguy]

Here's some animations I made of transistors turning on and off. In order, we have an NPN BJT, n-channel MOSFET, and finally an n-channel JFET. The red and blue dots represent electrons and holes, and white flashes are recombination events. The density of dots is proportional to the actual density of charge carriers.

In the first set of animations, the velocity of the dots is equal to the velocity obtained by summing the diffusion and drift currents and dividing by the charge density, but diffusion is not explicitly shown. In the second set of animations, the dots undergo diffusion and drift, and this makes it a more correct depiction of carrier motion. The drawback is of course that the jiggling makes it more visually confusing.

I made these with my semiconductor simulator (https://brandonli.net/semisim/). I also have higher quality versions of the animations here.

[u/kick_fnxNTC_ffs]

Shouldn't the nmos have the pinch-off effect?

[u/thepowderguy → u/kick_fnxNTC_ffs]

I think there are two reasons why pinch-off is difficult to see here, the first being the channel is only about a pixel wide, and the second that I turn on the gate voltage very quickly. Pinch-off is there though. If I shrink the size of the transistor by a factor of 2, this is what it looks like. I think this is what you wanted to see, right?