SBOSA11A March 2020 – March 2021 OPA2206

PRODUCTION DATA

- 1 Features
- 2 Applications
- 3 Description
- 4 Revision History
- 5 Pin Configuration and Functions
- 6 Specifications
- 7 Parameter Measurement Information
- 8 Detailed Description
- 9 Application and Implementation
- 10Power Supply Recommendations
- 11Layout
- 12Device and Documentation Support
- 13Mechanical, Packaging, and Orderable Information

- DGK|8

Designers often have questions about a
typical specification of an amplifier in order to design a more robust circuit. As a result
of natural variations in process technology and manufacturing procedures, every
specification of an amplifier exhibits some amount of deviation from the ideal value, such
as the input bias current of an amplifier. These deviations often follow *Gaussian*
(bell curve), or *normal* distributions. Circuit designers can leverage this
information to guardband their system, even when there is no minimum or maximum
specification in the *Electrical Characteristics*.

Figure 7-1 shows an example
distribution, where *µ*, is the mean of the distribution, and where *σ*, or
*sigma*, is the standard deviation of a system. For a specification that exhibits
this kind of distribution, approximately two-thirds (68.26%) of all units can be expected to
have a value within one standard deviation, or one sigma, of the mean (from *µ–σ* to
*µ+σ*).

Depending on the specification, values
listed in the *typical* column of *Electrical Characteristics* are represented in different ways. As a
general guideline, if a specification naturally has a nonzero mean (for example, gain
bandwidth), then the typical value is equal to the mean (µ). However, if a specification
naturally has a mean near zero (for example, input bias current), then the typical value is
equal to the mean plus one standard deviation (µ + σ) to most accurately represent the
typical value.

Use this chart to calculate the approximate
probability of a specification in a unit. For example, the OPA2206 typical input bias
current is ±0.1 nA; therefore, 68.2% of all devices are expected to have an input bias from
±0.1 nA. At 4*σ*, 99.9937% of the distribution has an input bias less than ±0.28 nA,
which means that 0.0063% of the population is outside of these limits, and corresponds to
approximately 1 in 15,873 units.

Units that are found to exceed any tested minimum or maximum specifications are removed from production material. For example, the OPA2206 has a maximum input bias of ±0.4 nA at 25°C, and although this value corresponds to approximately 6σ (~1 in 500 million units), TI removes any unit with a larger input bias from production material.

For specifications with no value in the minimum or maximum column, consider selecting a sigma value of sufficient guardband for your application, and design worst-case conditions using this value. This information should only be used to estimate the performance of a device.