APPLICATIONS INFORMATION
OPA350 series op amps are fabricated on a state-of-the-art 0.6
micron CMOS process. They are unity-gain stable and suit-
able for a wide range of general-purpose applications. Rail-to-
rail input/output make them ideal for driving sampling A/D
converters. They are also well suited for controlling the output
power in cell phones. These applications often require high
speed and low noise. In addition, the OPA350 series offers a
low cost solution for general-purpose and consumer video
applications (75Ω drive capability).
Excellent ac performance makes the OPA350 series well
suited for audio applications. Their bandwidth, slew rate,
low noise (5nV/√Hz), low THD (0.0006%), and small pack-
age options are ideal for these applications. The class AB
output stage is capable of driving 600Ω loads connected to
any point between V+ and ground.
Rail-to-rail input and output swing significantly increases
dynamic range, especially in low voltage supply applica-
tions. Figure 1 shows the input and output waveforms for
V
S
= +5, G = +1, R
L
= 1kΩ
5V
the OPA350 in unity-gain configuration. Operation is
from a single +5V supply with a 1kΩ load connected to
V
S
/2. The input is a 5Vp-p sinusoid. Output voltage swing
is approximately 4.95Vp-p.
Power supply pins should be bypassed with 0.01µF ceramic
capacitors.
OPERATING VOLTAGE
OPA350 series op amps are fully specified from +2.7V to
+5.5V. However, supply voltage may range from +2.5V to
+5.5V. Parameters are tested over the specified supply
range—a unique feature of the OPA350 series. In addition,
many specifications apply from –40°C to +85°C. Most
behavior remains virtually unchanged throughout the full
operating voltage range. Parameters that vary significantly
with operating voltage or temperature are shown in the
typical characteristics.
RAIL-TO-RAIL INPUT
The tested input common-mode voltage range of the OPA350
series 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 on Figure 2. The N-channel pair is
active for input voltages close to the positive rail, typically
(V+) – 1.8V to 100mV above the positive supply, while the
P-channel pair is on for inputs from 100mV below the
negative supply to approximately (V+) – 1.8V. There is a
small transition region, typically (V+) – 2V to (V+) – 1.6V, in
which both pairs are on. This 400mV transition region can
vary
±400mV
with process variation. Thus, the transition
region (both input stages on) can range from (V+) – 2.4V to
(V+) – 2.0V on the low end, up to (V+) – 1.6V to (V+) – 1.2V
on the high end.
V
IN
0
5V
V
OUT
0
FIGURE 1. Rail-to-Rail Input and Output.
V+
Reference
Current
V
IN
+
1.25V/div
V
IN
–
V
BIAS1
Class AB
Control
Circuitry
V
O
V
BIAS2
V–
(Ground)
FIGURE 2. Simplified Schematic.
8
OPA350, 2350, 4350
SBOS099A
ETC [ ETC ]
