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Analog Angle Article

Ultra-precision op amp pushes to zero drift, 36V rail

Remember that “ideal” op amp from basic-circuits class? The one with no drift, no offset, no errors, and no other “issues”? IC vendors are continually getting closer to that ideal: the Texas Instruments OPA2188 dual, ultra-precision op amp has low-enough drift that it is in the class often referred to as “zero-drift” by op amp vendors. [Incidentally, TI achieves this offset-voltage performance through design and process, not laser trim.]

But the typical voltage offset drift of 0.03μV/°C (0.085μV/°C maximum) is not the only specification which distinguishes this op amp (although TI says this is 4× better than the closest competitor). TI says this is the first zero-drift op amp capable of running from a 36V rail (or corresponding bipolar rails), making it a good fit for test and measurement, weight scales, flow meters, and medical instrumentation.

For those of you who live in the single-digit supply-rail world, and wonder why anyone would want 36V: it's those harsher electrical environments which need higher-voltage rails to maintain analog signal-chain SNR. Input common mode range extending from negative rail to within 1.5V of the positive rail saves additional circuitry and enables 5V, single-supply operation.

Despite the 36V rating, the quiescent current per amplifier is 475μA, enable portable medical applications. Also benefiting instrumentation applications, the op amp sports initial offset voltage of 25 μV and noise of just 8.8 nV/√Hz.

Tools and support include:

  • A universal evaluation module (EVM) which simplifies evaluation by allowing many different circuits to be constructed easily and quickly. The EVM is available today for $5.
  • A reference design and SPICE model in TINA-TI 9.1, a SPICE-based analog simulation program.
  • Software for analysis, application and calculation utilities, including Analog Filter Designer, FilterPro, and calculators for decibel, frequency/wavelength and op amp gain stage.

Availability, packaging and pricing: The OPA2188 is available today in a 3×5-mm MSOP package or 5×6-mm SOIC package, priced at $1.40 each in 1,000 unit lots.

For more information: download the data sheet at www.ti.com/opa2188ds-pr, or watch a video at www.ti.com/opa2188v-pr.

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