Matched OpAmps

[dknguyen]

I'm building something (3-phase BLDC BEMF zero-cross detector) that requires matching between 3 op amps and 3 comparators. Now, I've picked CMOS comparators and op-amps with the all the comparators being in one IC and all the op-amps being in another IC.

Does anyone know if I can rely on the offset voltages and currents being matched? I'm not sure how well matched things tend to be when they are on a single piece of silicon. THey must have pulled it off for transistor pairs in each op-amp, but they might have tried really hard to do so and whatever they did might not carry between op-amps on the ame piece of silicon. Especially CMOS since apparently one of the biggest problems with analog CMOS components is that it's hard to match CMOS transistors.

At least, I'm pretty sure they're on a single piece of silicon. I've never heard of anything like making 4 separate op-amps and sticking all 4 pieces of silicon into one package.

 

[GonzoEngineer]

My experience is that they will be very well matched, because they are on the same piece of silicon.

But the only way to really find out is to breadboard them up, with matching impedances, and measure what the deviation is.

(BTW.....I just have to ask......I know you are probaly Vietnamese, by the handle.......but is your avatar a picture of you?)

 

[dknguyen]

It is not.

 

[GonzoEngineer]

OK......back on thread.

You are very right in making sure all the comparators and op amps share the same package. It will minimize the offsets.