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Vos matching and tracking within a single die

Mark Liebendorfer
Prodigy 80 points
Other Parts Discussed in Thread: OPA387, OPA392, OPA182, OPA192

TI App Note SLOA059B "DC Parameters: Input Offset Voltage (VOS)" (Richard Palmer and Katherine Li), talks about op-amp input offset voltage but may not contain an answer to the following:

I'm designing a circuit that uses a quad op-amp IC.  I'm specifying a very low input offset voltage device (Vos) so the circuit can meet specifications.  However, if the Vos of all 4 devices on the chip matched (or came close) and tracked each other, that would be sufficient.

My question:  In a single-die multi-opamp package, are the offset voltages matched?   If not, are there devices which are better designed for matching than others?

My guess:  Automated Vos trimming probably disturbs what would otherwise be a perfect match.

  • 0
    TI__Guru 66441 points

    Hi Mark,

    The short answer to your question about Vos matching on multi-channel IC die is that there is no correlation between the channels  - the input voltage offsets of four channel quad is as random as offsets of four individual singles. Since each channel is designed to have zero offset, the actual offset comes from the random mismatches of diffusions (over etching or under etching) caused by the minimum geometry of lithographic process (min resolution) of the wafer process used for fabrication of ICs.

    The best thing you may do to get closest possible match is to use parts with extremely low offset.  Thus, package-level trimmed part (e-trim) like OPA392 (5V) or OPA192 (36V) or zero-drift parts (choppers or auto-zero) like OPA387 (5V) or OPA182 (36V) with maximum specified offset voltage limit within +/-3uV.to +/-25uV range would be the best way to go.

  • 0 in reply to Marek Lis
    Prodigy 80 points

    Marek,

    Thank you for your helpful reply. 

    Mark