OPA333A-EP Datasheet, PDF (8/19 Pages) Texas Instruments – 1.8-V MICROPOWER CMOS OPERATIONAL AMPLIFIERS ZERO-DRIFT SERIES

OPA333A-EP, OPA2333A-EP
SGLS383B – APRIL 2007 – REVISED JUNE 2008 ............................................................................................................................................................ www.ti.com
APPLICATION INFORMATION
The OPA333A and OPA2333A 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 ensuring 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 0.1 µV/°C or higher, depending on materials used.
Operating Voltage
The OPA333A and OPA2333A op amps operate over a power-supply range of 1.8 V to 5.5 V (±0.9 V to
±2.75 V). Supply voltages higher than 7 V (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 OPA333A and OPA2333A input common-mode voltage range extends 0.1 V beyond the supply rails. The
OPA333A 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 70 pA; 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 10 mA. This limitation is easily accomplished with an input resistor(see
Figure 1).
Current−limiting resistor
required if input voltage
exceeds supply rails by
≥ 0.5V.
I_OVERLOAD
10mA max
V_IN
5kΩ
+5V
OPA333A
V_OUT
Figure 1. Input Current Protection
Internal Offset Correction
The OPA333A and OPA2333A op amps use an auto-calibration technique with a time-continuous 350-kHz op
amp in the signal path. This amplifier is zero corrected every 8 µs using a proprietary technique. Upon power up,
the amplifier requires approximately 100 µs to achieve specified V_OS accuracy. This design has no aliasing or
flicker noise.
8
Submit Documentation Feedback
Copyright © 2007–2008, Texas Instruments Incorporated
Product Folder Link(s): OPA333A-EP OPA2333A-EP