OPA333_17 Datasheet, PDF (13/42 Pages) Texas Instruments – 1.8-V, microPower, CMOS Operational Amplifiers, Zero-Drift Series

www.ti.com
OPA333, OPA2333
SBOS351E – MARCH 2006 – REVISED DECEMBER 2015
Feature Description (continued)
7.3.2 Input Voltage
The OPA333 and OPA2333 input common-mode voltage range extends 0.1 V 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.
Typically, input bias current is approximately 70 pA; however, input voltages that exceed 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, as shown in Figure 18.
Current-limiting resistor
required if input voltage
exceeds supply rails by
³ 0.5 V.
I_OVERLOAD
10 mA max
V_IN
5 kW
+5 V
OPA333
V_OUT
Figure 18. Input Current Protection
7.3.3 Internal Offset Correction
The OPA333 and OPA2333 operational amplifiers use an auto-calibration technique with a time-continuous
350-kHz operational amplifier 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.
7.3.4 Achieving Output Swing to the Op Amp Negative Rail
Some applications require output voltage swings from 0 V to a positive full-scale voltage (such as 2.5 V) with
excellent accuracy. With most single-supply operational amplifiers, problems arise when the output signal
approaches 0 V, near the lower output swing limit of a single-supply operational amplifier. A good, single-supply
operational amplifier may swing close to single-supply ground, but does not reach ground. The output of the
OPA333 and OPA2333 can be made to swing to, or slightly below, ground on a single-supply power source. This
swing is achieved with the use of the use of another resistor and an additional, more negative power supply than
the operational amplifier negative supply. A pulldown resistor can be connected between the output and the
additional negative supply to pull the output down below the value that the output would otherwise achieve, as
shown in Figure 19.
V+ = +5 V
OPA333
V_OUT
V_IN
R_P = 20 kW
Op Amp V- = GND
-5 V
Additional
Negative
Supply
Figure 19. V_OUT Range to Ground
Copyright © 2006–2015, Texas Instruments Incorporated
Product Folder Links: OPA333 OPA2333
Submit Documentation Feedback
13