Collaborate Disseminate
If you want to measure resistance and you know Ohm’s law, it seems like you have an easy answer, right? Feed a known current through the thing you want to measure and read the voltage required. A little math, and that’s it. Or is it? If you are measuring reasonably …read more
Continue reading Circuit VR: Resistance Measurement with Four Wires
Usually, with Circuit VR we look at some circuit in detail with simulation — usually LTSpice. This one will be a little meta because I wanted to look at a capability in LTSpice which ironically is very useful, but not often used. Along the way, though, we’ll look at why you get maximum power transfer when your source impedance matches your load impedance. This is something you probably already know about, but it is interesting to look at in simulation if you know how to coax LTSpice — no pun intended — into showing you a meaningful graph.
The circuit …read more
Last time on Circuit VR, we looked at creating a very simple common emitter amplifier, but we didn’t talk about how to select the capacitor values, or much about why we wanted them. We are going to look at that this time, as well as how to use a second transistor in an emitter follower (or common collector) configuration to stiffen the amplifier’s ability to drive an output load.
Several readers wrote to point out that I’d pushed the Ic value a little high for a 2N2222. As it turns out, at least one of the calculations in the comments …read more
Sometimes I wish FETs had become practical before bipolar transistors. A FET is a lot more like a tube and amplifies voltages. Bipolar transistors amplify current and that makes them a bit harder to use. Recently, [Jenny List] did a series on transistor amplifiers including the topic of this Circuit VR, the common emitter amplifier. [Jenny] talked about biasing. I’ll start with biasing too, but in the next installment, I want to talk about how to use capacitors in this design and how to blend two amplifiers together and why you’d want to do that.
But before you can dive …read more