Discrete LM741 operational amplifier in DIL8
On the internet I came across a funny design: a discrete 741 operational amplifier. You can buy it at Adafruit, see the circuit also here:
Adafruit XL741 discrete 741 opamp
By the way, the LM741, which dates from 1967, is totally outdated. Today's opamps operate from a single supply voltage of a few volts and have a rail-to-rail input / output. The circuit of the LM741 contains the following parts:
- 20 x transistors
- 11 x resistors
- 1 x capacitor
I immediately started to consider whether it is possible to reduce this design to the original DIL8 package of the 741. This is indeed possible: you can see that the components fit on the PCB:
Discrete LM741 operational amplifier in DIL8
I don't have time to make it myself, so I make it a competition. The big challenge is that mounting the components has to be done by hand and with my solder paste dispenser:
Solder paste dispenser
It's a terribly precise job, but with my dispenser you can handle parts like 0201. The transistors must of course be very small, I am thinking of types such as the 2SC5658T2LQ with size VMT-3.
These are the rules:
- Dimension 0.4" x 0.3".
- Double sided PCB.
- Components on topside.
- You ust use VMT-3 like transistors
- The tin must be applied with my solder paste dispenser.
- The application of the tin, placing the components and soldering must be filmed.
- The opamp must be functional and tested well.
- Use 8 castellated mounting holes.
Who wants to win €250?
The first person who take up the challenge and carry it out successfully will receive €250 from me. To participate, please contact me.
High-density PCB
This project falls into the category high-density PCB, I think you need 0.1mm traces.
IBM Solid Logic Technology
I discovered that discrete integrated circuits actually existed as early as in 1964. IBM made custom hybrid circuits using discrete, glass-encapsulated transistors and diodes, with silk screened resistors on a ceramic substrate, forming an SLT modul, see Wikipedia.
IBM Solid Logic Technology SLT 1964
The dimensions are approximately equal to DIL8 by the way. In addition, they use a ball grid array, which apparently already existed also in 1964.
Other interesting projects with discrete transistors
Discussions
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