OPA2333AIDGKR Datasheet, PDF (8/28 Pages) Texas Instruments – 1.8V, microPOWER CMOS OPERATIONAL AMPLIFIERS Zero-Drift Series

OPA333
OPA2333
SBOS351C – MARCH 2006 – REVISED MAY 2007
APPLICATIONS INFORMATION
www.ti.com
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:
• Use low thermoelectric-coefficient conditions
(avoid dissimilar metals).
• Thermally isolate components from power
supplies or other heat sources.
• 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.
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.
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 18.
Current-limiting resistor
required if input voltage
exceeds supply rails by
³ 0.5V.
I_OVERLOAD
10mA max
V_IN
5kW
+5V
OPA333
V_OUT
Figure 18. 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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