APPLICATION INFORMATION

The OPA333A and OPA2333A are unity-gain stable and free from unexpected output phase reversal. They use a

Operating Voltage

Input Voltage

5k

Ω

OPA333A

10mA max

+5V

V

IN

V

OUT

I

OVERLOAD

Current−limiting resistor

required if input voltage

exceeds supply rails by

≥ 0.5V.

Internal Offset Correction

OPA333A-EP

,, OPA2333A-EP

SGLS383B – APRIL 2007 – REVISED JUNE 2008 ............................................................................................................................................................ www.ti.com

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.

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.

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).

Figure 1. Input Current Protection

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

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