I'm looking for a three-state inverting octal buffer for a replacement part for an old microprocessor lab. The package should be DIP. Ucc should be on pin 20. Chip select should be at pins 1 and 19 and active on low, so that the buffer is in high impedance state unless both enables are low. The input/output ports should be next to each other with even pins as input and odd as output. What this would be in practice is a 74540 IC with the described pin configuration or a 74366 with 20 pins. Help would be appreciated.
Three-state inverting octal buffer
bufferintegrated-circuitttl
Related Solutions
It seems after some discussion that you are looking for a buffer amplifier.
Digikey has a section for this. if you go to the main area for linear amplifiers and then select for buffer type and in stock you get quite a list. I selected for those with an input current of 2nA typical I got a relatively short list(like 10). This however does not give me an easy way to share the links, so you will have to click it yourself.
These are designed to give you the features you want and in a small package, now they normally come in groups of 2^n, so you will have to get a package of 8, but I am sure you can make it work.
Markrages had a bit of extra input to add in a comment:
Cautions about those buffer amps: Most of them are made for video signals and so they are high bandwidth / high current designs. That's a consideration if the circuit is battery powered. Also note that (the ones I looked at) are specialized, single vendor parts. More expensive and more availability risk than op-amps or transistors with standardized footprints. Engineers have a duty to only use oddball parts when their special features are necessary and relevant to the design.
I think you can do this with a single chip if you use a dual NAND gate with open-drain output like 74LVC2G38 (both gates below have open-drain output):
That runs off 1.65 to 3.3 V and it's available in a 2x3 mm 8-pin package, which is pretty close to SOT-23-sized.
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Best Answer
Consider a surface-mount version of the part, and combine it with a SOIC-to-DIP card to interface it with the old PCB.