The TT741: a discrete plug-in 741 replacement

Regular readers of this blog will have noticed that the 741 op amp features quite often. Apparently I’m not the only one with an interest in this venerable amplifier; the Wikipedia page on op amps contains a detailed description of the 741, several books and web sites describe and even celebrate the chip’s history, and you can buy a kit to make a large-size discrete replica from a company called Evil Mad Science Labs. I bought one of these because I thought it looked rather cool.

On the picture above you can see the 741SE compared to an original LM741. I got the SMD version of the kit, although you can also buy one that uses through-hole components and is shaped like a giant DIP package. Still, even the SMD version is enormous compared to the real chip, which got me thinking: would it be possible to make a discrete equivalent of the 741 in a space equivalent to an actual DIP chip?

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Fake (?) IR2104

I recently read a discussion on an electronics forum where someone had trouble getting an IR2104 to work correctly. He had bought these from a shady online store and could not get the correct signals to come out. I offered to analyze the chips, and one of the contributors to that discussion very kindly sent me a couple of them.

The IR2104 is a half-bridge MOSFET driver, which is used to drive the FETs in circuits like DC-DC converters and class-D power amplifiers. It’s made in a high-voltage CMOS process and is capable of driving the high-side FET at voltages up to 600V. The original designer and manufacturer is International Rectifier (IR), one of the first manufacturers of diodes, transistors and power management ICs. Currently the IR2104 is manufactured by Infineon, after it acquired IR in 2015.

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