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OPA354
OPA2354
OPA4354
SBOS233C − MARCH 2002− REVISED APRIL 2004
APPLICATIONS INFORMATION
The OPA354 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, dual, or quad 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 OPA354 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.
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.
RAIL-TO-RAIL OUTPUT
A class AB output stage with common-source transistors
is used to achieve rail-to-rail output. For high-impedance
loads (> 200Ω), the output voltage swing is typically
100mV from the supply rails. With 10Ω loads, a useful
output swing can be achieved while maintaining high
open-loop gain. See the typical characteristic curve
Output
Voltage Swing vs Output Current.
RAIL-TO-RAIL INPUT
The specified input common-mode voltage range of the
OPA354 extends 100mV beyond the supply rails. This is
achieved with a complementary input stagean
V+
Reference
Current
V
IN
+
V
IN
−
V
BIAS1
Class AB
Control
Circuitry
V
O
V
BIAS2
V−
(Ground)
Figure 1. Simplified Schematic
11
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