I was very kindly and generously gifted a Hewlett-Packard HP 9820A calculator by a good friend and ex-colleague. Unfortunately, the thing does not work, but I will try to get it working when I find the time between other things I have to do. The HP 9820A was the world’s first calculator that used an…
Yes, I finally managed to get an op amp to differentiate an input potential that varies over time. The top trace is the input potential. The bottom trace is the output from the op amp, showing the first derivative of the input. Huzzah! I connected the differentiator circuit to a sinusoidal input potential, and after…
Analysing circuits with two different power supplies can be tricky. There are a few approaches one can take. In this video, I show firstly how Kirchhoff’s Laws can be used with simultaneous equations to brute-force answers, and how to take a slightly more elegant approach by using the principle of superposition.
The atom joke is also a pet hate of mine because it’s just wrong
One can see the same potential applied to both inputs of the op amp, causing 0V output potential. That made sense. When connecting the inverting input pin to half the potential of the output (using two 10 kΩ fixed resistors as a potential divider), the output potential became 10V. Well, half of 10V is 5V, so that would make the inverting input potential 5V, the same as in the first case, yet the output potential is different.
Whilst I’m sure it was still impressive and exciting looking at ‘rainbow clouds’, it was a big let down compared to the prospect of looking at an aurora this far South.
The latest video is about what we can do with the electromagnetic radiation we detect from stars and galaxies.
I have recently got back from Edinburgh, where I saw this very large sextant (see picture).