OPA2631 Datasheet, PDF (11/18 Pages) Burr-Brown (TI) – Dual, Low Power, Single-Supply OPERATIONAL AMPLIFIER

APPLICATIONS INFORMATION
WIDEBAND VOLTAGE-FEEDBACK OPERATION
The OPA2631 is a unity-gain stable, very high-speed, volt-
age-feedback op amp designed for single-supply operation
(+3V to +10V). The input stage supports input voltages
below ground, and to within 1.0V of the positive supply. The
complementary common-emitter output stage provides an
output swing to within 30mV of ground and 130mV of the
positive supply. It is compensated to provide stable opera-
tion with a wide range of resistive loads.
Figure 1 shows the AC-coupled, gain of +2 configuration
used for the +5V Specifications and Typical Performance
Curves. For test purposes, the input impedance is set to 50Ω
with a resistor to ground. Voltage swings reported in the
Specifications are taken directly at the input and output pins.
For the circuit of Figure 1, the total effective load on the
output at high frequencies is 150Ω || 1500Ω. The 1.50kΩ
resistors at the non-inverting input provide the common-
mode bias voltage. Their parallel combination equals the DC
resistance at the inverting input, minimizing the output DC
offset.
+V_S = 5V
6.8µF
+
1.50kΩ
0.1µF
0.1µF
V_IN
53.6Ω
1/2
1.50kΩ OPA2631
V_OUT
R_L
150Ω
R_G
0.1µF 750Ω
R_F
750Ω
+V_S
2
FIGURE 1. AC-Coupled Signal—Resistive Load to Supply
Midpoint.
Figure 2 shows the DC-coupled, gain of +2 configuration
used for the +3V Specifications and Typical Performance
Curves. For test purposes, the input impedance is set to 50Ω
with a resistor to ground. Though not strictly a “rail-to-rail”
design, this part comes very close, while maintaining excel-
lent performance. It will deliver ≈ 2.9Vp-p on a single +3V
supply with 61MHz bandwidth. The 374Ω and 2.26kΩ
resistors at the input level-shift V_IN so that V_OUT is within
the allowed output voltage range when V_IN = 0. See the
typical performance curves for information on driving ca-
pacitive loads.
+V_S = 3V
6.8µF
+
2.26kΩ
0.1µF
374Ω
V_IN
57.6Ω
1/2
OPA2631
R_G
562Ω
R_F
750Ω
V_OUT
R_L
150Ω
+V_S
2
FIGURE 2. DC-Coupled Signal—Resistive Load to Supply
Midpoint.
SINGLE-SUPPLY ADC CONVERTER INTERFACE
The front page shows a DC-coupled, single-supply, dual
ADC (Analog-to-Digital Converter) driver circuit. Many
systems are now requiring +3V supply capability of both the
ADC and its driver. The OPA2631 provides excellent per-
formance in this demanding application. Its large input and
output voltage ranges, and low distortion support converters
such as the ADS901 shown in this figure. The input level-
shifting circuitry was designed so that V_IN can be between
0V and 0.5V, while delivering an output voltage of 1V to 2V
for the ADS901.
OPA2631
11
SBOS067A