APPLICATIONS INFORMATION
OPA743 series op amps can operate on 1.1mA quiescent
current from a single (or split) supply in the range of 3.5V
to 12V (±1.75V to
±6V),
making them highly versatile and
easy to use. The OPA743 is unity-gain stable and offers
7MHz bandwidth and 10V/µs slew rate.
Rail-to-rail input and output swing helps maintain dynamic
range, especially in low supply applications. Figure 1 shows
the input and output waveforms for the OPA743 in unity-
gain configuration. On a
±6V
supply with a 100kΩ load
connected to V
S
/2. The output is tested to swing within
100mV to the rail.
Power-supply pins should be bypassed with 1000pF ceramic
capacitors in parallel with 1µF tantalum capacitors.
+V
I
OVERLOAD
10mA max
V
IN
R
V–
OPA743
V
OUT
FIGURE 2. Input Current Protection for Voltages Exceeding
the Supply Voltage.
INPUT VOLTAGE
Device inputs are protected by ESD diodes that will conduct if
the input voltages exceed the power supplies by more than
approximately 300mV. Momentary voltages greater than 300mV
beyond the power supply can be tolerated if the current is limited
to 10mA. This is easily accomplished with an input resistor, in
series with the op amp input as shown in Figure 2. Many input
signals are inherently current-limited to less than 10mA; there-
fore, a limiting resistor is not always required. The OPA743
features no phase inversion when the inputs extend beyond
supplies if the input current is limited, as seen in Figure 3.
8
Input
6
4
2
2V/div
G = +1, V
S
±
6V
0
–2
–4
–6
Output (Inverted on osciloscope)
–8
20µs/div
FIGURE 1. Rail-to-Rail Input and Output.
OPERATING VOLTAGE
OPA743 series op amps are fully specified and guaranteed
from 3.5V to 12V over a temperature range of –40ºC to
+85ºC. Parameters that vary significantly with operating
voltages or temperature are shown in the Typical Character-
istics.
RAIL-TO-RAIL INPUT
The input common-mode voltage range of the OPA743 series
extends 100mV beyond the supply rails at room temperature.
This is achieved with a complementary input stage—an N-
channel input differential pair in parallel with a P-channel
differential pair. The N-channel pair is active for input volt-
ages close to the positive rail, typically (V+) – 2.0V to 100mV
above the positive supply, while the P-channel pair is on for
inputs from 100mV below the negative supply to approxi-
mately (V+) – 1.5V. There is a small transition region,
typically (V+) – 2.0V to (V+) – 1.5V, in which both pairs are
on. This 500mV transition region can vary
±100mV
with
process variation. Thus, the transition region (both stages on)
can range from (V+) – 2.1V to (V+) – 1.4V on the low end,
up to (V+) – 1.9V to (V+) – 1.6V on the high end. Most rail-
to-rail op amps on the market use this two input stage
approach, and exhibit a transition region where CMRR, offset
voltage, and THD may vary compared to operation outside
this region.
V
S
=
±6V,
V
IN
= 13Vp-p, G = +1
2V/div
20µs/div
FIGURE 3. OPA743—No Phase Inversion with Inputs
Greater than the Power-Supply Voltage.
RAIL-TO-RAIL OUTPUT
A class AB output stage with common-source transistors is
used to achieve rail-to-rail output. This output stage is
capable of driving 1kΩ loads connected to any point be-
tween V+ and V–. For light resistive loads (> 100kΩ), the
output voltage can swing to 100mV from the supply rail.
With 1kΩ resistive loads, the output can swing to within
325mV from the supply rails while maintaining high open-
loop gain (see the typical performance curve “Output Volt-
age Swing vs Output Current”).
OPA743
SBOS201
9
BURR-BROWN [ BURR-BROWN CORPORATION ]
