op-amp replacement for digital line driver?

Question

Hi! I'm trying to source a replacement part for a board I didn't design. For some reason, a digital line driver was used by mistake. I'm not entirely sure what the originally intended IC was to be (the pcb is part of a break-out shield for a Bare Bones Arduino, with nine

2A channels that drive various actuators and three sensor channels for control).

The incorrect chip is an 74HCT125N (quad buffer/line driver). One of the engineering consultants has suggested looking for a somewhat pin compatible quad op-amp and shorting the negative input to the output.

I'm not super-familiar with the pin-outs on op-amps, so I thought I'd see if I could find any recommendations. The datasheet for the line driver is up at:

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The I/Os for the line driver are:

1: 1oE: output Enable (inverted)
2: 1A: data in
3: 1Y: data out
4: 2oE: output Enable (inverted)
5: 2A: data in
6: 2Y: data out
7: GND

8: 3oE: output Enable (inverted)

9: 3A: data in
10: 3Y: data out
11: 4oE: output Enable (inverted)
12: 4A: data in
13: 4Y: data out
14: Vcc

Any suggestions would be greatly appreciated!

Cheers, L

George Herold · Accepted Answer

I don't know of any 'non-standard' quad opamps.  The standard quadopamp has a pinout that looks nothing like that.  For starters, thepower pins are in the middle of the package, (pins 4 and 11).Sorry,George H.

Liav · Answer

Ack. Sorry, I made a bit of a mistake with the right hand side of thepinout:8: 3Y,9: 3A10: 3oE11: 4Y12: 4A13: 4oE14: Vcc

Liav · Answer

I suspect this might be a bit of a goose chase.L

Tim Wescott · Answer

I don't know what your "engineering consultant" was thinking, but I think you're right.You probably need an adapter board, or a board spin, or a _lot_ of green wires.-- Tim WescottWescott Design ServicesDo you need to implement control loops in software?"Applied Control Theory for Embedded Systems" was written for you.See details at

whit3rd · Answer

I'm finding the question unclear. If the 'digital line driver' is a mistake, is some or all of the pinout really relevant? You mentioned 2A drive on the 'shield' (interface board), is that function supposed to be part of this chip?

What are the inputs of the intended function, and what are the outputs? 'Enable' and 'data in' are appropriate labels for tristate logic inputs, is the output intended to be tristate logic? Or is it open-collector drive?

And, if this is 'a board I didn't design' but is for an Arduino, is it something that can be traced to a schematic/parts list online?

Jasen Betts · Answer

why was this considered a mistake?look for another consultant?-- ?? 100% natural

op-amp replacement for digital line driver?

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