APPLICATIONS INFORMATION
OPA342 series op amps are unity gain stable and can operate
on a single supply, making them highly versatile and easy to
use.
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 OPA342 in
unity-gain configuration. Operation is from V
S
= +5V with
a 10kΩ load connected to V
S
/2. The input is a 5Vp-p
sinusoid. Output voltage is approximately 4.997Vp-p.
Power supply pins should be by passed with 0.01µF ceramic
capacitors.
OPERATING VOLTAGE
OPA342 series op amps are fully specified and guaranteed
from +2.7V to +5.5V. In addition, many specifications apply
from –40ºC to +85ºC. Parameters that vary significantly
with operating voltages or temperature are shown in the
Typical Performance Curves.
RAIL-TO-RAIL INPUT
The input common-mode voltage range of the OPA342
series extends 300mV 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
300mV above the positive supply, while the P-channel pair
is on for inputs from 300mV below the negative supply to
approximately (V+) –1.3V. There is a small transition re-
gion, typically (V+) – 1.5V to (V+) – 1.1V, in which both
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. For more information on
designing with rail-to-rail input op amps, see Figure 3
“Design Optimization with Rail-to-Rail Input Op Amps.”
Input
5V
G = +1, V
S
= +5V
0V
Output (inverted on scope)
5µs/div
FIGURE 1. Rail-to-Rail Input and Output.
1V/div
V+
Reference
Current
V
IN
+
V
IN
–
V
BIAS1
Class AB
Control
Circuitry
V
O
V
BIAS2
V–
(Ground)
FIGURE 2. Simplified Schematic.
8
OPA342, 2342, 4342
SBOS106A
BURR-BROWN [ BURR-BROWN CORPORATION ]
