OPA202 datasheet(21/48 Pages) TI1

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0.1n

10n

100n

1µ

10µ

100

10k

100k

10M

Source Resistance, R

S (Ÿ)

C003

OPA211

OPA202

Resistor Noise

S = 6 kŸ

OPA202, OPA2202, OPA4202

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SBOS812F – OCTOBER 2017 – REVISED FEBRUARY 2020

Product Folder Links: OPA202 OPA2202 OPA4202

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7.3.2 Output Current Limit

The output current of the OPAx202 is limited by internal circuitry to ±35 mA (sinking or sourcing) to protect the

device if the output is accidentally shorted. This short-circuit current depends on temperature, as Figure 37

shows.

7.3.3 Noise Performance

Figure 42 shows the total circuit noise for varying source impedances with the operational amplifier in a unity-

gain configuration (with no feedback resistor network and therefore no additional noise contributions). The

OPAx202 and OPA211 are shown with total circuit noise calculated. The op amp itself contributes a voltage

noise component and a current noise component. The voltage noise is commonly modeled as a time-varying

component of the offset voltage. The current noise is modeled as the time-varying component of the input bias

current and reacts with the source resistance to create a voltage component of noise. Therefore, the lowest noise

op amp for a given application depends on the source impedance. For low source impedance, current noise is

negligible and voltage noise dominates. The OPAx202 have both low voltage noise and low current noise

because of the super-beta bipolar junction transistor (super-β BJT) input of the op amp. As a result, the current

noise contribution of the OPAx202 is negligible for most practical source impedances, which makes the series

the better choice for applications with high source impedance.

The equation in Figure 42 shows the calculation of the total circuit noise with these parameters:

•

en = voltage noise

•

In = current noise

•

RS = source impedance

•

k = Boltzmann's constant = 1.38 × 10–23 J/K

•

T = temperature in kelvins (K)

For more details on calculating noise, see Basic Noise Calculations.

NOTE: For source resistances (RS) greater than 6 kΩ, the OPAx202 is a lower-noise option compared to the

OPA211, as shown in Figure 42.

Figure 42. Noise Performance of the OPAx202 vs the OPA211 in a Unity-Gain Buffer Configuration

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