A forum for people who enjoy electronics as a hobby.
The 7-segment display as designed is only good for the exercises included. Only one character is hard wired to be displayed at a time. Opening it up you find one 100 Ohm resistor on the positive power lead only. This doesn't bwork if you intend to demonstrate a 7 segment decoder and a counter. So we modify it.
And there is no general purpose operational amplifier. So we create one. You can buy empty cases from them. All I needed for a basic op amp is seven snap buttons so I got one of the bred cases as used for the CMOS logic gates. MCP6021 was used. It is Rail-to-rail In and out, designed to work on a single 5 Volt rail. I mounted it on a small PC board with a socket so it could be changed easily. Most op amps will work but many lack the rail to rail capability of the MCP6021.