OPA340-EP_15 Datasheet, PDF (9/19 Pages) Texas Instruments – SINGLE-SUPPLY RAIL-TO-RAIL OPERATIONAL AMPLIFIERS

OPA340-EP
www.ti.com
SBOS433A – AUGUST 2008 – REVISED APRIL 2011
APPLICATION INFORMATION
The OPA340 is fabricated on a state-of-the-art
0.6-micron CMOS process. It is unity-gain stable and
suitable for a wide range of general-purpose
applications. Rail-to-rail input/output makes it ideal for
driving sampling A/D converters. In addition, excellent
ac performance makes it well-suited for audio
applications. The class AB output stage is capable of
driving 600-Ω 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 23 shows the input and output
waveforms for the OPA340 in unity-gain
configuration. Operation is from a single 5-V supply
with a 10-kΩ load connected to V_S/2. The input is a
5-V_PP sinusoid. Output voltage is approximately
4.98 V_PP.
Power-supply pins should be bypassed with 0.01-μF
ceramic capacitors.
V_S = +5, G = +1, R_L = 10kW
5
V_IN
5
V_OUT
125°C. Most behavior remains nearly unchanged
throughout the full operating voltage range.
Parameters that vary significantly with operating
voltages or temperature are shown in Typical
Characteristics.
Rail-to-Rail Input
The input common-mode voltage range of the
OPA340 extends 500 mV 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 in
Figure 24). The N-channel pair is active for input
voltages close to the positive rail, typically
(V+) – 1.3 V to 500 mV above the positive supply,
while the P-channel pair is on for inputs from 500 mV
below the negative supply to approximately
(V+) – 1.3 V. There is a small transition region,
typically (V+) – 1.5 V to (V+) – 1.1 V, in which both
pairs are on. This 400-mV transition region can vary
±300 mV with process variation. Thus, the transition
region (both stages on) can range from (V+) – 1.8 V
to (V+) – 1.4 V on the low end, up to (V+) – 1.2 V to
(V+) – 0.8 V on the high end.
The OPA340 is laser-trimmed to reduce the offset
voltage difference between the N-channel and
P-channel input stages, resulting in improved
common-mode rejection and a smooth transition
between the N-channel pair and the P-channel pair.
However, within the 400-mV transition region PSRR,
CMRR, offset voltage, offset drift, and THD may be
degraded compared to operation outside this region.
0
Figure 23. Rail-to-Rail Input and Output
Operating Voltage
The OPA340 is fully specified from 2.7 V to 5 V.
Parameters are ensured over the specified supply
range—a unique feature of the OPA340 series. In
addition, many specifications apply from –55°C to
A double-folded cascode adds the signal from the two
input pairs and presents a differential signal to the
class AB output stage. Normally, input bias current is
approximately 200 fA; however, input voltages
exceeding the power supplies by more than 500 mV
can cause excessive current to flow in or out of the
input pins. Momentary voltages greater than 500 mV
beyond the power supply can be tolerated if the
current on the input pins is limited to 10 mA. This is
easily accomplished with an input resistor, as shown
in Figure 25. Many input signals are inherently
current-limited to less than 10 mA; therefore, a
limiting resistor is not required.
Copyright © 2008–2011, Texas Instruments Incorporated
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