Our two “dis-integrated circuit” kits are the Three Fives Discrete 555 Timer, and the XL741 Discrete Op-Amp. These two kits are functional, transistor-level replicas of the original NE555 and μA741 (respectively), which are two of the most popular integrated circuits of all time.
Last year, we wrote up a detailed educational supplement for the Three Fives kit, that works through its circuit diagram and discusses its principles of operation down to the transistor level. Today, we are doing the same for the XL741 kit, and releasing an educational supplement that explains how a ‘741 op-amp IC works internally, down to its bare transistors and resistors:
This ability to peek inside the circuit makes the XL741 a unique educational tool. In what follows, we’ll work through the circuit diagram, discuss the theory of operation of the ‘741 op-amp, and present some opportunities for experiments and further exploration.
You can download the supplement here: XL741 Principles of Operation (1.1 MB PDF)
- Get the XL741 kit at our store.
- Our original article here, announcing the XL741 kit
- Main XL741 documentation page at our documentation wiki
Steve W. wrote in to share his improvement on the method for making wire bundles we wrote about:
I’ve used the bend-it-over-and-stuff-it-in-the-chuck approach, but was not fully happy with it.
So I drilled a 1/8″ hole in the back of a binder clip. The drilling is easy if you clip a ~3/8 scrap of wood.
A 4-40 SHCS screw long enough to allow me to actuate the clip was not threaded all the way to the head, so I used a 1/4″ spacer between the binder clip and the 4-40 nut. (Pan head screws are usually 100% threaded, but I would have had to look in the dreaded ‘other’ box to find one of those). Having the nut up against the chuck acted as a lock-nut. I had been surprised when I first tried this that I did not have to work harder to keep it from loosening. I had expected I might need a lock washer, and/or a second nut to lock the first.
Just grabbing the wires with the binder clip (my original plan) was not secure. So I wrap the wires 180 degrees around a screwdriver bit and put that in the clip.
Works great, and it is quick to pop in and out when twisting many groups of wires.
Thanks for sharing your hack and sending the photos!
The article Can Analog Circuits Inspire Budding Engineers? over at Planet Analog discusses preparing students for dealing with real world circuitry by getting them started with analog circuits.
By building, probing, and observing the signals and their changes in these circuits without any code requirements, students can get a real feel for otherwise abstract concepts such as voltage, current, and more.
The author uses examples of projects and kits including our very own Three Fives Kit.