APPLICATIONS INFORMATION
OPA343 series op amps are fabricated on a state-of-the-art
0.6 micron CMOS process. They are unity-gain stable and
suitable for a wide range of general purpose applications.
Rail-to-rail input/output make them ideal for driving sam-
pling A/D converters. In addition, excellent ac performance
makes them well-suited for audio 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 supply applications.
Figure 1 shows the input and output waveforms for the
OPA343 in unity-gain configuration. Operation is from a
single +5V supply with a 10kΩ load connected to V
S
/2.
The input is a 5Vp-p sinusoid. Output voltage is approxi-
mately 4.98Vp-p.
V
S
= +5, G = +1, R
L
= 10kΩ
Power supply pins should be bypassed with 0.01µF ceramic
capacitors.
OPERATING VOLTAGE
OPA343 series op amps are fully specified from +2.7V to
+5V. However, supply voltage may range from +2.5V to
+5.5V. Parameters are guaranteed over the specified supply
range—a unique feature of the OPA343 series. In addition,
many specifications apply from –40°C to +85°C. Most
behavior remains virtually unchanged throughout the full
operating voltage range. Parameters which vary signifi-
cantly with operating voltages or temperature are shown in
the typical performance curves.
RAIL-TO-RAIL INPUT
The input common-mode voltage range of the OPA343
series extends 500mV beyond the supply rails. This is
achieved with a complementary input stage—an N-channel
input differential pair in parallel with a P-channel differen-
tial pair (see Figure 2). The N-channel pair is active for input
voltages close to the positive rail, typically (V+) –1.3V to
500mV above the positive supply. The P-channel pair is on
for inputs from 500mV below the negative supply to ap-
proximately (V+) –1.3V.
There is a small transition region, typically (V+) –1.5V to
(V+) –1.1V, in which both input pairs are on. This 400mV
transition region can vary
±300mV
with process variation.
Thus, the transition region (both stages on) can range from
(V+) –1.8V to (V+) –1.4V on the low end, up to (V+) –1.2V
to (V+) –0.8V on the high end. Within the 400mV transition
region PSRR, CMRR, offset voltage, offset drift, and THD
may be degraded compared to operation outside this region.
5
V
IN
2V/div
5
V
OUT
0
FIGURE 1. Rail-to-Rail Input and Output.
V+
Reference
Current
V
IN
+
V
IN
–
V
BIAS1
Class AB
Control
Circuitry
V
O
V
BIAS2
V–
(Ground)
FIGURE 2. Simplified Schematic.
®
OPA343, 2343, 4343
8
BURR-BROWN [ BURR-BROWN CORPORATION ]
