OPA333 Datasheet, PDF (7/18 Pages) Burr-Brown (TI) – 1.8V, microPOWER CMOS OPERATIONAL AMPLIFIERS Zer-PI Drift Series

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APPLICATIONS INFORMATION
The OPA333 and OPA2333 are unity-gain stable and free
from unexpected output phase reversal. They use a
proprietary auto-calibration technique to provide low offset
voltage and very low drift over time and temperature. For
lowest offset voltage and precision performance, circuit
layout and mechanical conditions should be optimized.
Avoid temperature gradients that create thermoelectric
(Seebeck) effects in the thermocouple junctions formed
from connecting dissimilar conductors. These
thermally-generated potentials can be made to cancel by
assuring they are equal on both input terminals. Other
layout and design considerations include:
D Use low thermoelectric-coefficient conditions (avoid
dissimilar metals).
D Thermally isolate components from power supplies or
other heat sources.
D Shield op amp and input circuitry from air currents,
such as cooling fans.
Following these guidelines will reduce the likelihood of
junctions being at different temperatures, which can cause
thermoelectric voltages of 0.1µV/°C or higher, depending
on materials used.
OPA333
OPA2333
SBOS351 − MARCH 2006
INPUT VOLTAGE
The OPA333 and OPA2333 input common-mode voltage
range extends 0.1V beyond the supply rails. The OPA333
is designed to cover the full range without the troublesome
transition region found in some other rail-to-rail amplifiers.
Normally, input bias current is about 70pA; however, input
voltages exceeding the power supplies can cause
excessive current to flow into or out of the input pins.
Momentary voltages greater than the power supply can be
tolerated if the input current is limited to 10mA. This
limitation is easily accomplished with an input resistor, as
shown in Figure 1.
Current−limiting resistor
required if input voltage
exceeds supply rails by
≥ 0.5V.
I_OVERLOAD
10mA max
V_IN
5kΩ
+5V
OPA333
V_OUT
OPERATING VOLTAGE
The OPA333 and OPA2333 op amps operate over a
power-supply range of +1.8V to +5.5V (±0.9V to ±2.75V).
Supply voltages higher than +7V (absolute maximum) can
permanently damage the device. Parameters that vary
over supply voltage or temperature are shown in the
Typical Characteristics section of this data sheet.
Figure 1. Input Current Protection
INTERNAL OFFSET CORRECTION
The OPA333 and OPA2333 op amps use an
auto-calibration technique with a time-continuous 350kHz
op amp in the signal path. This amplifier is zero-corrected
every 8µs using a proprietary technique. Upon power-up,
the amplifier requires approximately 100µs to achieve
specified V_OS accuracy. This design has no aliasing or
flicker noise.
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