OPA357 Datasheet, PDF (11/23 Pages) Burr-Brown (TI) – 250MHz, Rail-to-Rail I/O, CMOS Operational Amplifier with Shutdown

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APPLICATIONS INFORMATION
The OPA357 is a CMOS, rail-to-rail I/O, high-speed,
voltage-feedback operational amplifier designed for video,
high-speed, and other applications. It is available as a
single or dual op amp.
The amplifier features a 100MHz gain bandwidth, and
150V/µs slew rate, but it is unity-gain stable and can be
operated as a +1V/V voltage follower.
OPERATING VOLTAGE
The OPA357 is specified over a power-supply range of
+2.7V to +5.5V (±1.35V to ±2.75V). However, the supply
voltage may range from +2.5V to +5.5V (±1.25V to
±2.75V). Supply voltages higher than 7.5V (absolute
maximum) can permanently damage the amplifier.
Parameters that vary over supply voltage or temperature
are shown in the Typical Characteristics section of this
data sheet.
ENABLE FUNCTION
The OPA357’s Enable function is implemented using a
Schmitt trigger. The amplifier is enabled by applying a TTL
HIGH voltage level (referenced to V−) to the Enable pin.
Conversely, a TTL LOW voltage level (referenced to V−)
will disable the amplifier, reducing its supply current from
4.9mA to only 3.4µA per amplifier. Independent Enable
pins are available for each channel (dual version),
providing maximum design flexibility. For portable
battery-operated applications, this feature can be used to
greatly reduce the average current and thereby extend
battery life.
OPA357
OPA2357
SBOS235C − MARCH 2002− REVISED MAY 2004
The Enable input can be modeled as a CMOS input gate
with a 100kΩ pull-up resistor to V+. This pin should be
connected to a valid high or low voltage or driven, not left
open circuit.
The enable time is 100ns and the disable time is only 30ns.
This allows the OPA357 to be operated as a gated
amplifier, or to have its output multiplexed onto a common
output bus. When disabled, the output assumes a
high-impedance state.
RAIL-TO-RAIL INPUT
The specified input common-mode voltage range of the
OPA357 extends 100mV beyond the supply rails. This is
achieved with a complementary input stagean
N-channel input differential pair in parallel with a
P-channel differential pair, as shown in Figure 1. The
N-channel pair is active for input voltages close to the
positive rail, typically (V+) − 1.2V to 100mV above the
positive supply, while the P-channel pair is on for inputs
from 100mV below the negative supply to approximately
(V+) − 1.2V. There is a small transition region, typically
(V+) − 1.5V to (V+) − 0.9V, in which both pairs are on. This
600mV transition region can vary ±500mV with process
variation. Thus, the transition region (both input stages on)
can range from (V+) − 2.0V to (V+) − 1.5V on the low end,
up to (V+) − 0.9V to (V+) − 0.4V on the high end.
A double-folded cascode adds the signal from the two
input pairs and presents a differential signal to the class AB
output stage.
V+
Reference
Current
V_IN+
V_IN−
V_BIAS1
Class AB
Control
V_O
Circuitry
V_BIAS2
V−
(Ground)
Figure 1. Simplified Schematic
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