on the high end. Within the 200mV transition region PSRR,
CMRR, offset voltage, offset drift, and THD may be degraded
compared to operation outside this region.
APPLICATIONS INFORMATION
OPA348 series op amps are unity-gain stable and suitable
for a wide range of general-purpose applications.
The OPA348 series features wide bandwidth and unity-gain
stability with rail-to-rail input and output for increased dynamic
range. Figure 1 shows the input and output waveforms for the
OPA348 in unity-gain configuration. Operation is from a single
+5V supply with a 100kΩ load connected to VS/2. The input is
a 5Vp-p sinusoid. Output voltage is approximately 4.98Vp-p.
OFFSET VOLTAGE
vs FULL COMMON-MODE VOLTAGE RANGE
2
1.5
1
Power-supply pins should be bypassed with 0.01µF ceramic
capacitors.
0.5
0
–0.5
–1
G = +1V/V, VS = +5V
V–
V+
Output (Inverted on Scope)
5V
–1.5
–2
–0.5
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
5.5
Common-Mode Voltage (V)
FIGURE 2. Behavior of Typical Transition Region at Room
Temperature.
0V
20µs/div
RAIL-TO-RAIL INPUT
The input common-mode range extends from (V–) – 0.2V to
(V+) + 0.2V. For normal operation, inputs should be limited to
this range. The absolute maximum input voltage is 500mV
beyond the supplies. Inputs greater than the input common-
mode range but less than the maximum input voltage, while not
valid, will not cause any damage to the op amp. Unlike some
other op amps, if input current is limited the inputs may go
beyond the power supplies without phase inversion, as shown
in Figure 3.
FIGURE 1. The OPA348 Features Rail-to-Rail Input/Output.
OPERATING VOLTAGE
OPA348 series op amps are fully specified and tested from
+2.5V to +5.5V. However, supply voltage may range from
+2.1V to +5.5V. Parameters are tested over the specified
supply range—a unique feature of the OPA348 series. In
addition, all temperature specifications apply from –40°C to
+125°C. Most behavior remains virtually unchanged through-
out the full operating voltage range. Parameters that vary
significantly with operating voltages or temperature are shown
in the Typical Characteristics.
VIN
G = +1V/V, VS = +5V
COMMON-MODE VOLTAGE RANGE
5V
The input common-mode voltage range of the OPA348 series
extends 200mV beyond the supply rails. This is achieved
with a complementary input stage—an N-channel input differ-
ential pair in parallel with a P-channel differential pair. The
N-channel pair is active for input voltages close to the positive
rail, typically (V+) – 1.2V to 300mV above the positive supply,
while the P-channel pair is on for inputs from 300mV below the
negative supply to approximately (V+) – 1.4V. There is a small
transition region, typically (V+) – 1.4V to (V+) – 1.2V, in which
both pairs are on. This 200mV transition region, shown in
Figure 2, can vary ±300mV with process variation. Thus, the
transition region (both stages on) can range from (V+) – 1.7V
to (V+) – 1.5V on the low end, up to (V+) – 1.1V to (V+) – 0.9V
VOUT
0V
10µs/div
FIGURE 3. OPA348—No Phase Inversion with Inputs Greater
than the Power-Supply Voltage.
OPA348, 2348, 4348
7
SBOS213C
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