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Build a working transistor-scale replica of the classic and ubiquitous analog workhorse.
The "XL741" Discrete Operational Amplifier kit from Evil Mad Scientist Laboratories is a faithful and functional transistor-scale replica of the μA741 op-amp integrated circuit, the classic and ubiquitous analog workhorse.
An Operational Amplifier, or "op-amp" as they are commonly known, is one of the most useful and common types of analog electronic circuit building blocks. The original μA741 was designed by Dave Fullagar and released by Fairchild in 1968. It quickly became the quintessential and most popular op-amp of all time. While newer op-amp designs may outperform the μA741 in just about every possible respect (speed, noise, voltage range, and so on), the 741 remains widely beloved and in active production today — over 45 years later.
The XL741 kit was designed by Eric Schlaepfer, in collaboration with Evil Mad Scientist Laboratories. The kit is lovingly designed to resemble an (overgrown) integrated circuit, based around an extra-thick matte-finish printed circuit board. It comes complete with a beautiful aluminum display stand that gives the circuit board eight legs in the shape of DIP-packaged integrated circuit pins.
Download Datasheet (1.6 MB PDF file).
Building the kit
The XL741 kit is sold as an easy-to-build soldering kit. It includes the circuit board, resistors, transistors and capacitor that make up the electrical circuit as well as printed assembly instructions. The kit also comes complete with the "IC Leg" stand, and 8 color coded thumbscrew terminal posts.
To build the XL741 kit, basic electronic soldering skill and tools are required, but no additional knowledge of electronics is presumed or required. You provide standard soldering tools: a soldering iron + solder and small ("flush") wire clippers, as well as a Phillips head screwdriver
The kit features easy "through-hole" construction ("No surface-mount nothin' nowhere!"), and (assuming that you have prior soldering experience) should take roughly an hour to build.
Using the "XL741" Discrete Op-Amp
The XL741 circuit is a direct implementation of the "equivalent circuit" from the original Fairchild μA741 datasheet, built up using resistors, individual 2N3904 and 2N3906 transistors, and one capacitor. It comes with terminal posts and solder points so that you can actually connect to it and build up classic and functional op-amp circuits. Using those terminal posts and solder points, you can hook up with with bare wires, lugs, alligator clips, and/or solder joints— however you see fit.
And unlike the chip version, you can even hook up probes to monitor what goes on inside the circuit.
Some performance characteristics are different than those of 741 integrated circuits; please refer to the Absolute Maximum Ratings and Electrical Characteristics in the datasheet for additional details.
Materials and construction