LOW POWER, SINGLE-SUPPLY, RAIL-TO-RAIL
OPERATIONAL AMPLIFIERS
Micro
Amplifier
™ Series
© 2000 Burr-Brown Corporation PDS-1486A Printed in U.S.A. April, 2000
®
FEATURES
●RAIL-TO-RAIL INPUT
●RAIL-TO-RAIL OUTPUT (within 1mV)
●LOW QUIESCENT CURRENT: 150µA typ
●
Micro
SIZE PACKAGES
SOT23-5
MSOP-8
TSSOP-14
●GAIN-BANDWIDTH
OPA344: 1MHz, G ≥ 1
OPA345: 3MHz, G ≥ 5
●SLEW RATE
OPA344: 0.8V/µs
OPA345: 2V/µs
●THD + NOISE: 0.006%
APPLICATIONS
● PCMCIA CARDS
● DATA ACQUISITION
● PROCESS CONTROL
● AUDIO PROCESSING
●COMMUNICATIONS
●ACTIVE FILTERS
●TEST EQUIPMENT
DESCRIPTION
The OPA344 and OPA345 series rail-to-rail CMOS
operational amplifiers are designed for precision, low-
power, miniature applications. The OPA344 is unity
gain stable, while the OPA345 is optimized for gains
greater than or equal to five, and has a gain-bandwidth
product of 3MHz.
The OPA344 and OPA345 are optimized to operate on
a single supply from 2.5V and up to 5.5V with an input
common-mode voltage range that extends 300mV
beyond the supplies. Quiescent current is only
250µA (max).
Rail-to-rail input and output make them ideal for driving
sampling analog-to-digital converters. They are also well
suited for general purpose and audio applicaitons and
providing I/V conversion at the output of D/A converters.
Single, dual and quad versions have identical specs for
design flexibility.
A variety of packages are available. All are specified for
operation from –40ºC to 85ºC. A SPICE macromodel is
available for design analysis.
OPA345
OPA2345
OPA4345
OPA344
OPA2344
OPA4344
1
2
3
5
4
V+
–In
Out
V–
+In
OPA344, OPA345
SOT23-5
1
2
3
4
8
7
6
5
NC
V+
Out
NC
NC
–In
+In
V–
OPA344, OPA345
SO-8, 8-Pin DIP (OPA344 Only)
1
2
3
4
8
7
6
5
V+
Out B
–In B
+In B
Out A
–In A
+In A
V–
OPA2344, OPA2345
SO-8, MSOP-8, 8-Pin DIP (OPA2344 Only)
A
B
1
2
3
4
5
6
7
14
13
12
11
10
9
8
Out D
–In D
+In D
–V
+In C
–In C
Out C
Out A
–In A
+In A
+V
+In B
–In B
Out B
OPA4344, OPA4345
TSSOP-14, SO-14, 14-PIn DIP (OPA4344 Only)
AD
BC
International Airport Industrial Park • Mailing Address: PO Box 11400, Tucson, AZ 85734 • Street Address: 6730 S. Tucson Blvd., Tucson, AZ 85706 • Tel: (520) 746-1111
Twx: 910-952-1111 • Internet: http://www.burr-brown.com/ • Cable: BBRCORP • Telex: 066-6491 • FAX: (520) 889-1510 • Immediate Product Info: (800) 548-6132
®
OPA342
OPA4344
OPA344
OPA345
For most current data sheet and other product
information, visit www.burr-brown.com
SBOS107
2
®
OPA344, 2344, 4344
OPA345, 2345, 4345
SPECIFICATIONS: VS = 2.7V to 5.5V
At TA = +25°C, RL = 10kΩ connected to VS/ 2 and VOUT = VS/ 2, unless otherwise noted.
Boldface limits apply over the temperature range, TA = –40°C to +85°C.
OPA344NA, UA, PA
OPA2344EA, UA, PA
OPA4344EA, UA, PA
PARAMETER CONDITION MIN TYP MAX UNITS
OFFSET VOLTAGE
Input Offset Voltage VOS VS = +5.5V, VCM = VS/2 ±0.2 ±1mV
Over Temperature ±0.8 ±1.2 mV
vs Temperature dVOS/dT ±3µV/°C
vs Power Supply PSRR VS = 2.7V to 5.5V, VCM < (V+) -1.8V 30 200 µV/V
Over Temperature VS = 2.7V to 5.5V, VCM < (V+) -1.8V 250 µV/V
Channel Separation, dc 0.2 µV/V
f = 1kHz 130 dB
INPUT BIAS CURRENT
Input Bias Current IB±0.2 ±10 pA
Over Temperature See Typical Curve pA
Input Offset Current IOS ±0.2 ±10 pA
NOISE
Input Voltage Noise f = 0.1 to 50kHz 8 µVrms
Input Voltage Noise Density enf = 10kHz 30 nV/√Hz
Current Noise Density inf = 10kHz 0.5 fA/√Hz
INPUT VOLTAGE RANGE
Common-Mode Voltage Range VCM –0.3 (V+) + 0.3 V
Common-Mode Rejection Ratio CMRR VS = +5.5V, –0.3V < VCM < (V+)-1.8 76 92 dB
Over Temperature VS = +5.5V, –0.3V < VCM < (V+)-1.8 74 dB
Common-Mode Rejection CMRR VS = +5.5V, –0.3V < VCM < 5.8V 70 84 dB
Over Temperature VS = +5.5V, –0.3V < VCM < 5.8V 68 dB
Common-Mode Rejection CMRR VS = +2.7V, –0.3V < VCM < 3V 66 80 dB
Over Temperature VS = +2.7V, –0.3V < VCM < 3V 64 dB
INPUT IMPEDANCE
Differential 1013 || 3 Ω || pF
Common-Mode 1013 || 6 Ω || pF
OPEN-LOOP GAIN
Open-Loop Voltage Gain AOL RL = 100kΩ, 10mV < VO < (V+) –10mV 104 122 dB
Over Temperature RL = 100kΩ, 10mV < VO < (V+) –10mV 100 dB
RL = 5kΩ, 400mV < VO < (V+) –400mV 96 120 dB
Over Temperature RL = 5kΩ, 400mV < VO < (V+) –400mV 90 dB
FREQUENCY RESPONSE CL = 100pF
Gain-Bandwidth Product GBW 1 MHz
Slew Rate SR 0.8 V/µs
Settling Time, 0.1% VS = 5.5V, 2V Step 5 µs
0.01% VS = 5.5V, 2V Step 8 µs
Overload Recovery Time VIN • G = VS2.5 µs
Total Harmonic Distortion + Noise THD+N VS = 5.5V, VO = 3Vp-p, G = 1, f = 1kHz 0.006 %
OUTPUT
Voltage Output Swing from Rail(1) RL = 100kΩ, AOL ≥ 96dB 1 mV
RL = 100kΩ, AOL ≥ 104dB 3 10 mV
Over Temperature RL = 100kΩ, AOL ≥ 100dB 10 mV
RL = 5kΩ, AOL ≥ 96dB 40 400 mV
Over Temperature RL = 5kΩ, AOL ≥ 90dB 400 mV
Short-Circuit Current ISC ±15 mA
Capacitive Load Drive CLOAD See Typical Curve
POWER SUPPLY
Specified Voltage Range VS2.7 5.5 V
Operating Voltage Range 2.5 to 5.5 V
Quiescent Current (per amplifier) IQVS = 5.5V, IO = 0 150 250 µA
Over Temperature 300 µA
TEMPERATURE RANGE
Specified Range –40 85 °C
Operating Range –55 125 °C
Storage Range –65 150 °C
Thermal Resistance
θ
JA
SOT23-5 Surface Mount 200 °C/W
MSOP-8 Surface Mount 150 °C/W
8-Pin DIP 100 °C/W
SO-8 Surface Mount 150 °C/W
TSSOP-14 Surface Mount 100 °C/W
14-Pin DIP 80 °C/W
SO-14 Surface Mount 100 °C/W
NOTE: (1) Output voltage swings are measured between the output and power-supply rails.
3
®
OPA344, 2344, 4344
OPA345, 2345, 4345
SPECIFICATIONS: VS = 2.7V to 5.5V
At TA = +25°C, RL = 10kΩ connected to VS/ 2 and VOUT = VS/ 2, unless otherwise noted.
Boldface limits apply over the temperature range, TA = –40°C to +85°C.
OPA345NA, UA
OPA2345EA, UA
OPA4345EA, UA
PARAMETER CONDITION MIN TYP MAX UNITS
OFFSET VOLTAGE
Input Offset Voltage VOS VS = +5.5V, VCM = VS/2 ±0.2 ±1mV
Over Temperature ±0.8 ±1.2 mV
vs Temperature dVOS/dT ±3µV/°C
vs Power Supply PSRR VS = 2.7V to 5.5V, VCM < (V+) -1.8V 30 200 µV/V
Over Temperature VS = 2.7V to 5.5V, VCM < (V+) -1.8V 250 µV/V
Channel Separation, dc 0.2 µV/V
f = 1kHz 130 dB
INPUT BIAS CURRENT
Input Bias Current IB±0.2 ±10 pA
Over Temperature See Typical Curve pA
Input Offset Current IOS ±0.2 ±10 pA
NOISE
Input Voltage Noise f = 0.1 to 50kHz 8 µVrms
Input Voltage Noise Density enf = 10kHz 30 nV/√Hz
Current Noise Density inf = 10kHz 0.5 fA/√Hz
INPUT VOLTAGE RANGE
Common-Mode Voltage Range VCM –0.3 (V+) + 0.3 V
Common-Mode Rejection Ratio CMRR VS = +5.5V, –0.3V < VCM < (V+)-1.8 76 92 dB
Over Temperature VS = +5.5V, –0.3V < VCM < (V+)-1.8 74 dB
Common-Mode Rejection Ratio CMRR VS = +5.5V, –0.3V < VCM < 5.8V 70 84 dB
Over Temperature VS = +5.5V, –0.3V < VCM < 5.8V 68 dB
Common-Mode Rejection Ratio CMRR VS = +2.7V, –0.3V < VCM < 3V 66 80 dB
Over Temperature VS = +2.7V, –0.3V < VCM < 3V 64 dB
INPUT IMPEDANCE
Differential 1013 || 3 Ω || pF
Common-Mode 1013 || 6 Ω || pF
OPEN-LOOP GAIN
Open-Loop Voltage Gain AOL RL = 100kΩ, 10mV < VO < (V+) –10mV 104 122 dB
Over Temperature RL = 100kΩ, 10mV < VO < (V+) –10mV 100 dB
RL = 5kΩ, 400mV < VO < (V+) –400mV 96 120 dB
Over Temperature RL = 5kΩ, 400mV < VO < (V+) –400mV 90 dB
FREQUENCY RESPONSE CL = 100pF
Gain-Bandwidth Product GBW 3 MHz
Slew Rate SR 2 V/µs
Settling Time, 0.1% G = 5, 2V Output Step 1.5 µs
0.01% G = 5, 2V Output Step 1.6 µs
Overload Recovery Time VIN • G = VS2.5 µs
Total Harmonic Distortion + Noise THD+N VS = 5.5V, VO = 2.5Vp-p, G = 5, f = 1kHz 0.006 %
OUTPUT
Voltage Output Swing from Rail(1) RL = 100kΩ, AOL ≥ 96dB 1 mV
RL = 100kΩ, AOL ≥ 104dB 3 10 mV
Over Temperature RL = 100kΩ, AOL ≥ 100dB 10 mV
RL = 5kΩ, AOL ≥ 96dB 40 400 mV
Over Temperature RL = 5kΩ, AOL ≥ 90dB 400 mV
Short-Circuit Current ISC ±15 mA
Capacitive Load Drive CLOAD See Typical Curve
POWER SUPPLY
Specified Voltage Range VS2.7 5.5 V
Operating Voltage Range 2.5 to 5.5 V
Quiescent Current (per amplifier) IQVS = 5.5V, IO = 0 150 250 µA
Over Temperature 300 µA
TEMPERATURE RANGE
Specified Range –40 85 °C
Operating Range –55 125 °C
Storage Range –65 150 °C
Thermal Resistance
θ
JA
SOT23-5 Surface Mount 200 °C/W
MSOP-8 Surface Mount 150 °C/W
SO-8 Surface Mount 150 °C/W
TSSOP-14 Surface Mount 100 °C/W
SO-14 Surface Mount 100 °C/W
NOTE: (1) Output voltage swings are measured between the output and power-supply rails.
4
®
OPA344, 2344, 4344
OPA345, 2345, 4345
PACKAGE SPECIFIED
DRAWING TEMPERATURE PACKAGE ORDERING TRANSPORT
PRODUCT PACKAGE NUMBER RANGE MARKING NUMBER(1) MEDIA
OPA344NA SOT23-5 331 –40°C to +85°C B44 OPA344NA /250 Tape and Reel
"""""OPA344NA /3K Tape and Reel
OPA344UA SO-8 182 –40°C to +85°C OPA344UA OPA344UA Rails
"""""OPA344UA /2K5 Tape and Reel
OPA344PA 8-Pin Dip 006 –40° C to +85°C OPA344PA OPA344PA Rails
OPA2344EA MSOP-8 337 –40°C to +85°C C44 OPA2344EA /250 Tape and Reel
"""""OPA2344EA/2K5 Tape and Reel
OPA2344UA SO-8 182 –40°C to +85°C OPA2344UA OPA2344UA Rails
"""""OPA2344UA /2K5 Tape and Reel
OPA2344PA 8-Pin DIP 006 –40°C to +85°C OPA2344PA OPA2344PA Rails
OPA4344EA TSSOP-14 357 –40°C to +85°C OPA4344EA OPA4344EA/250 Rails
"""""OPA4344EA/2K5 Tape and Reel
OPA4344UA SO-14 235 –40°C to +85°C OPA4344UA OPA4344UA Rails
"""""OPA4344UA /2K5 Tape and Reel
OPA4344PA 14-Pin DIP 010 –40°C to +85°C OPA4344PA OPA4344PA Rails
OPA345NA SOT23-5 331 –40°C to +85°C A45 OPA345NA/250 Tape and Reel
" " " " " OPA345NA/3K Tape and Reel
OPA345UA SO-8 182 –40°C to +85°C OPA345UA OPA345UA Rails
" " " " " OPA345UA/2K5 Tape and Reel
OPA2345EA MSOP-8 337 –40°C to +85°C B45 OPA2345EA/250 Tape and Reel
"""""OPA2345EA/2K5 Tape and Reel
OPA2345UA SO-8 182 –40°C to +85°C OPA2345UA OPA2345UA Rails
"""""OPA2345UA /2K5 Tape and Reel
OPA4345EA TSSOP-14 357 –40°C to +85°C OPA4345EA OPA4345EA/250 Tape and Reel
"""""OPA4345EA/2K5 Tape and Reel
OPA4345UA SO-14 235 –40°C to +85°C OPA4345UA OPA4345UA Rails
"""""OPA4345UA /2K5 Tape and Reel
NOTE: (1) Models with a slash (/) are available only in Tape and Reel in the quantities indicated (e.g., /2K5 indicates 2500 devices per reel). Ordering 2500 pieces
of “OPA344UA/2K5” will get a single 2500-piece Tape and Reel.
PACKAGE/ORDERING INFORMATION
Supply Voltage, V+ to V- ................................................................... 7.5V
Signal Input Terminals, Voltage(2) .....................(V–) –0.5V to (V+) +0.5V
Current(2) .................................................... 10mA
Output Short-Circuit(3) .............................................................. Continuous
Operating Temperature ..................................................–55°C to +125°C
Storage Temperature .....................................................–65°C to +150°C
Junction Temperature...................................................................... 150°C
Lead Temperature (soldering, 10s)................................................. 300°C
ESD Tolerance (Human Body Model) ............................................ 4000V
NOTES: (1) Stresses above these ratings may cause permanent damage.
Exposure to absolute maximum conditions for extended periods may
degrade device reliability. These are stress ratings only. Functional opera-
tion of the device at these conditions, or beyond the specified operating
conditions, is not implied. (2) Input terminals are diode-clamped to the power
supply rails. Input signals that can swing more than 0.5V beyond the supply
rails should be current-limited to 10mA or less. (3) Short-circuit to ground,
one amplifier per package.
ABSOLUTE MAXIMUM RATINGS(1) ELECTROSTATIC
DISCHARGE SENSITIVITY
This integrated circuit can be damaged by ESD. Burr-Brown
recommends that all integrated circuits be handled with
appropriate precautions. Failure to observe proper handling
and installation procedures can cause damage. ESD damage
can range from subtle performance degradation to complete
device failure. Precision integrated circuits may be more
susceptible to damage because very small parametric
changes could cause the device not to meet its published
specifications.
5
®
OPA344, 2344, 4344
OPA345, 2345, 4345
TYPICAL PERFORMANCE CURVES
At TA = +25°C, VS = +5V, and RL = 10kΩ connected to VS/2, unless otherwise noted.
POWER SUPPLY AND COMMON-MODE
REJECTION RATIO vs FREQUENCY
10
Rejection Ratio (dB)
Frequency (Hz)
100 1k 10k 100k
100
80
60
40
20
10
+PSRR
CMRR
–PSRR
MAXIMUM OUTPUT VOLTAGE vs FREQUENCY
100k
Maximum Output Voltage (Vp-p)
Frequency (Hz)
1M 10M
6
5
4
3
2
1
0
OPA344
V
S
= +2.7V
V
S
= +5.5V
V
S
=
+5V
OPA345
CHANNEL SEPARATION vs FREQUENCY
100
Channel Separation (dB)
Frequency (Hz)
1k 10k 100k 1M
140
120
100
80
60
Dual and quad devices.
G = 1, all channels.
Quad measured channel
A to D or B to C—other
combinations yield improved
rejection.
VOLTAGE AND CURRENT NOISE
SPECTRAL DENSITY vs FREQUENCY
1
Voltage Noise (nV/√Hz)
Frequency (Hz)
10 100 1k 10k 100k 1M 10M
10000
1000
100
10
Current Noise (fA/√Hz)
100
10
1
0.1
V
N
I
N
OPEN-LOOP GAIN/PHASE vs FREQUENCY
0.1 1
Gain (dB)
0
30
60
90
120
150
180
Phase (°)
Frequency (Hz)
10 100 1k 10k 100k 1M 10M
120
100
80
60
40
20
0
Gain
Phase
OPA345
OPEN-LOOP GAIN/PHASE vs FREQUENCY
0.1 1
Gain (dB)
0
30
60
90
120
150
180
Phase (°)
Frequency (Hz)
10 100 1k 10k 100k 1M 10M
120
100
80
60
40
20
0
Gain
Phase
OPA344
6
®
OPA344, 2344, 4344
OPA345, 2345, 4345
TYPICAL PERFORMANCE CURVES (Cont.)
At TA = +25°C, VS = +5V, and RL = 10kΩ connected to VS/2, unless otherwise noted.
TOTAL HARMONIC DISTORTION + NOISE
vs FREQUENCY
20
THD+N (%)
Frequency (Hz)
100 1k 10k 20k
1
0.1
0.010
0.001
OPA344: G = 1
OPA345: G = 5
OPEN-LOOP GAIN, COMMON-MODE REJECTION RATIO,
AND POWER-SUPPLY REJECTION vs TEMPERATURE
A
OL
–75
A
OL
, CMRR, PSRR (dB)
Temperature (°C)
–25 0 25–50 50 12575 100
140
120
100
80
60
40
20
0
CMRR
PSRR
INPUT BIAS CURRENT vs TEMPERATURE
–75
Input Bias Current (pA)
Temperature (°C)
–25 0 25–50 10050 75 125
10000
1000
100
10
1
0.1
QUIESCENT CURRENT AND
SHORT-CIRCUIT CURRENT vs TEMPERATURE
–75 –50 0
Quiescent Current (µA)
Temperature (°C)
25 50 100
I
Q
+I
SC
–I
SC
75–25 125
200
175
150
135
100
75
50
25
0
Short-Circuit Current (mA)
40
35
30
25
20
15
10
5
0
SLEW RATE vs TEMPERATURE
–75
Slew Rate (V/µs)
Temperature (°C)
250
SR–
SR–
SR+
SR+
7550–25–50 125100
3.0
2.5
2.0
1.5
1.0
0.5
0
OPA345
OPA344
INPUT BIAS CURRENT
vs COMMON-MODE VOLTAGE
–1
Input Bias Current (pA)
Common-Mode Voltage (V)
012 4356
6
4
2
0
–2
–4
–6
V+
Supply
V–
Supply
Input voltage ≤ –0.3V
can cause op amp output
to lock up. See text.
7
®
OPA344, 2344, 4344
OPA345, 2345, 4345
TYPICAL PERFORMANCE CURVES (Cont.)
At TA = +25°C, VS = +5V, and RL = 10kΩ connected to VS/2, unless otherwise noted.
QUIESCENT CURRENT AND
SHORT-CIRCUIT CURRENT vs SUPPLY VOLTAGE
Quiescent Current (µA)
Supply Voltage (V)
23456
+I
SC
–I
SC
I
Q
160
155
150
145
140
Short-Circuit Current (mA)
20
15
10
5
0
OPEN-LOOP GAIN vs OUTPUT VOLTAGE SWING
140
130
120
110
100
Open-Loop Gain (dB)
Output Voltage Swing from Rail (mV)
120 100 80 60 40 20 0
R
L
= 5kΩ
R
L
= 100kΩ
OUTPUT VOLTAGE SWING vs OUTPUT CURRENT
0
Output Voltage (V)
Output Current (mA)
5
≈≈
10 15 20
V+
(V+) – 1
(V+) – 2
2
1
0
85°C
25°C
–40°C
85°C
25°C
–40°C
QUIESCENT CURRENT
PRODUCTION DISTRIBUTION
Population
Quiescent Current (µA)
100
115
130
145
160
175
190
205
220
235
250
OFFSET VOLTAGE
PRODUCTION DISTRIBUTION
Population
Offset Voltage (µV)
–1000
–800
–600
–400
–200
0
200
400
600
800
1000
OFFSET VOLTAGE DRIFT
PRODUCTION DISTRIBUTION
Population
Offset Voltage Drift (µV/°C)
–10
–8
–6
–4
–2
0
2
4
6
8
10
8
®
OPA344, 2344, 4344
OPA345, 2345, 4345
TYPICAL PERFORMANCE CURVES (Cont.)
At TA = +25°C, VS = +5V, and RL = 10kΩ connected to VS/2, unless otherwise noted.
70
60
50
40
30
20
10
0
Small-Signal Overshoot (%)
SMALL-SIGNAL OVERSHOOT vs LOAD CAPACITANCE
100 1k 10k10 Load Capacitance (pF)
G = –5
G = –10, +10
G = +5
OPA345
20mV/div
5µs/div
SMALL-SIGNAL STEP RESPONSE: OPA345
G = +5, RL = 10kΩ, CL = 100pF
OPA345
20mV/div
5µs/div
SMALL-SIGNAL STEP RESPONSE: OPA344
G = +1, RL = 10kΩ, CL = 100pF
OPA344
5µs/div
LARGE-SIGNAL STEP RESPONSE: OPA344
G = +1, RL = 10kΩ, CL = 100pF
1V/div
OPA344
5µs/div
LARGE-SIGNAL STEP RESPONSE: OPA345
G = +5, RL = 10kΩ, CL = 100pF
1V/div
OPA345
SMALL-SIGNAL OVERSHOOT vs LOAD CAPACITANCE
1
Small-Signal Overshoot (%)
Load Capacitance (pF)
10 100 1k 10k
G = –1
G = –5
50
45
40
35
30
25
20
15
10
5
0
OPA344
G = +5
G = +1
9
®
OPA344, 2344, 4344
OPA345, 2345, 4345
APPLICATIONS INFORMATION
OPA344 series op amps are unity gain stable and can operate
on a single supply, making them highly versatile and easy to
use. OPA345 series op amps are optimized for applications
requiring higher speeds with gains of 5 or greater.
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 OPA344 in
unity-gain configuration. Operation is from VS = +5V with
a 10kΩ load connected to VS/2. The input is a 5Vp-p
sinusoid. Output voltage is approximately 4.997Vp-p.
Power supply pins should be by passed with 0.01pF ceramic
capacitors.
OPERATING VOLTAGE
OPA344 and OPA345 series op amps are fully specified and
guaranteed from +2.7V to +5.5V. In addition, many specifi-
cations 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 OPA344 and
OPA345 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
differential 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 region, 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 de-
graded 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.”
FIGURE 2. Simplified Schematic.
V
BIAS1
V
BIAS2
V
IN
+V
IN
–
Class AB
Control
Circuitry V
O
V–
(Ground)
V+
Reference
Current
FIGURE 1. Rail-to-Rail Input and Output.
5µs/div
1V/div
Output (inverted on scope)
Input G = +1, VS = +5V
5V
0V
10
®
OPA344, 2344, 4344
OPA345, 2345, 4345
COMMON-MODE REJECTION
The CMRR for the OPA344 and OPA345 is specified in
several ways so the best match for a given application may
be used. First, the CMRR of the device in the common-mode
range below the transition region (VCM < (V+) – 1.8V) is
given. This specification is the best indicator of the capabil-
ity of the device when the application requires use of one of
the differential input pairs. Second, the CMRR at VS = 5.5V
over the entire common-mode range is specified. Third, the
CMRR at VS = 2.7V over the entire common-mode range is
provided. These last two values include the variations seen
through the transition region.
INPUT VOLTAGE BEYOND THE RAILS
If the input voltage can go more than 0.3V below the
negative power supply rail (single-supply ground), special
precautions are required. If the input voltage goes suffi-
ciently negative, the op amp output may lock up in an
inoperative state. A Schottky diode clamp circuit will pre-
vent this—see Figure 4. The series resistor prevents exces-
sive current (greater than 10mA) in the Schottky diode and
in the internal ESD protection diode, if the input voltage can
exceed the positive supply voltage. If the signal source is
limited to less than 10mA, the input resistor is not required.
RAIL-TO-RAIL OUTPUT
A class AB output stage with common-source transistors is
used to achieve rail-to-rail output. This output stage is
capable of driving 600Ω loads connected to any potential
between V+ and ground. For light resistive loads (> 50kΩ),
the output voltage can typically swing to within 1mV from
supply rail. With moderate resistive loads (2kΩ to 50kΩ),
the output can swing to within a few tens of milli-volts from
the supply rails while maintaining high open-loop gain. See
the typical performance curve “Output Voltage Swing vs
Output Current.”
VO
VIN
VBV+
Non-Inverting Gain
VCM = VIN
VO
VB
VIN V+
Inverting Amplifier
VCM = VB
VO
VIN
V+
G = 1 Buffer
VCM = VIN = VO
FIGURE 3. Design Optimization with Rail-to-Rail Input Op Amps.
Rail-to-rail op amps can be used in virtually any op amp
configuration. To achieve optimum performance, how-
ever, applications using these special double-input-stage
op amps may benefit from consideration of their special
behavior.
In many applications, operation remains within the com-
mon-mode range of only one differential input pair.
However some applications exercise the amplifier through
the transition region of both differential input stages.
Although the two input stages are laser trimmed for
excellent matching, a small discontinuity may occur in
this transition. Careful selection of the circuit configura-
tion, signal levels and biasing can often avoid this transi-
tion region.
DESIGN OPTIMIZATION WITH RAIL-TO-RAIL INPUT OP AMPS
With a unity-gain buffer, for example, signals will traverse
this transition at approximately 1.3V below V+ supply
and may exhibit a small discontinuity at this point.
The common-mode voltage of the non-inverting ampli-
fier is equal to the input voltage. If the input signal always
remains less than the transition voltage, no discontinuity
will be created. The closed-loop gain of this configura-
tion can still produce a rail-to-rail output.
Inverting amplifiers have a constant common-mode volt-
age equal to VB. If this bias voltage is constant, no
discontinuity will be created. The bias voltage can gener-
ally be chosen to avoid the transition region.
FIGURE 4. Input Current Protection for Voltages Exceed-
ing the Supply Voltage.
1kΩ
OPA344
10mA max
V+
V
IN
V
OUT
I
OVERLOAD
IN5818
Schottky diode is required only
if input voltage can go more
than 0.3V below ground.
CAPACITIVE LOAD AND STABILITY
The OPA344 in a unity-gain configuration and the OPA345
in gains greater than 5 can directly drive up to 250pF pure
capacitive load. Increasing the gain enhances the amplifier’s
ability to drive greater capacitive loads. See the typical
11
®
OPA344, 2344, 4344
OPA345, 2345, 4345
performance curve “Small-Signal Overshoot vs Capacitive
Load.” In unity-gain configurations, capacitive load drive
can be improved by inserting a small (10Ω to 20Ω) resistor,
RS, in series with the output, as shown in Figure 5. This
significantly reduces ringing while maintaining dc perfor-
mance for purely capacitive loads. However, if there is a
resistive load in parallel with the capacitive load, a voltage
divider is created, introducing a dc error at the output and
slightly reducing the output swing. The error introduced is
proportional to the ratio RS/RL, and is generally negligible.
FIGURE 6. OPA344 in Noninverting Configuration Driving ADS7822.
FIGURE 7. Speech Bandpass Filtered Data Acquisition System.
DRIVING A/D CONVERTERS
The OPA344 and OPA345 series op amps are optimized for
driving medium-speed sampling A/D converters. The
OPA344 and OPA345 op amps buffer the A/D’s input
capacitance and resulting charge injection while providing
signal gain.
Figures 6 shows the OPA344 in a basic noninverting con-
figuration driving the ADS7822. The ADS7822 is a 12-bit,
micro-power sampling converter in the MSOP-8 package.
When used with the low-power, miniature packages of the
OPA344, the combination is ideal for space-limited, low-
power applications. In this configuration, an RC network at
the A/D’s input can be used to filter charge injection.
Figure 7 shows the OPA2344 driving an ADS7822 in a
speech bandpass filtered data acquisition system. This small,
low-cost solution provides the necessary amplification and
signal conditioning to interface directly with an electret
microphone. This circuit will operate with VS = +2.7V to
+5V with less than 500µA quiescent current.
FIGURE 5. Series Resistor in Unity-Gain Configuration
Improves Capacitive Load Drive.
10Ω to
20Ω
OPA344
V+
V
IN
V
OUT
R
S
R
L
C
L
C
3
33pF
V+
GND
3
18
4
5
6
7
–IN
+IN
2
C
2
DCLOCK
Serial
Interface
1000pF
R
1
1.5kΩR
4
20kΩ
R
5
20kΩ
R
6
100kΩ
R
8
150kΩ
R
9
510kΩ
R
7
51kΩ
D
OUT
V
REF
V+ = +2.7V to 5V
CS/SHDN
C
1
1000pF
Electret
Microphone
(1)
G = 100
Passband 300Hz to 3kHz
R
3
1MΩ
R
2
1MΩ
NOTE: (1) Electret microphone
powered by R
1
.
ADS7822
12-Bit A/D
1/2
OPA2344 1/2
OPA2344
ADS7822
12-Bit A/D
DCLOCK
D
OUT
CS/SHDN
OPA344
+5V
V
IN
V+
2
+In
3
–In
V
REF
8
4GND
Serial
Interface
1
0.1µF 0.1µF
7
6
5
NOTE: A/D Input = 0 to V
REF
V
IN
= 0V to 5V for
0V to 5V output.
RC network filters high frequency noise.
500Ω
3300pF
PACKAGING INFORMATION
ORDERABLE DEVICE STATUS(1) PACKAGE TYPE PACKAGE DRAWING PINS PACKAGE QTY
OPA2344EA/250 ACTIVE VSSOP DGK 8 250
OPA2344EA/2K5 ACTIVE VSSOP DGK 8 2500
OPA2344PA ACTIVE PDIP P 8 50
OPA2344UA ACTIVE SOIC D 8 100
OPA2344UA/2K5 ACTIVE SOIC D 8 2500
OPA2345EA/250 ACTIVE VSSOP DGK 8 250
OPA2345EA/2K5 ACTIVE VSSOP DGK 8 2500
OPA2345UA ACTIVE SOIC D 8 100
OPA2345UA/2K5 ACTIVE SOIC D 8 2500
OPA344NA/250 ACTIVE SOP DBV 5 250
OPA344NA/3K ACTIVE SOP DBV 5 3000
OPA344PA ACTIVE PDIP P 8 50
OPA344UA ACTIVE SOIC D 8 100
OPA344UA/2K5 ACTIVE SOIC D 8 2500
OPA345NA/250 ACTIVE SOP DBV 5 250
OPA345NA/3K ACTIVE SOP DBV 5 3000
OPA345UA ACTIVE SOIC D 8 100
OPA345UA/2K5 ACTIVE SOIC D 8 2500
OPA4344EA/250 ACTIVE TSSOP PW 14 250
OPA4344EA/2K5 ACTIVE TSSOP PW 14 2500
OPA4344PA ACTIVE PDIP N 14 25
OPA4344UA ACTIVE SOIC D 14 58
OPA4344UA/2K5 ACTIVE SOIC D 14 2500
OPA4345EA/250 ACTIVE TSSOP PW 14 250
OPA4345EA/2K5 ACTIVE TSSOP PW 14 2500
OPA4345UA ACTIVE SOIC D 14 58
OPA4345UA/2K5 ACTIVE SOIC D 14 2500
(1) The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in
a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
PACKAGE OPTION ADDENDUM
www.ti.com 3-Oct-2003
IMPORTANT NOTICE
Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications,
enhancements, improvements, and other changes to its products and services at any time and to discontinue
any product or service without notice. Customers should obtain the latest relevant information before placing
orders and should verify that such information is current and complete. All products are sold subject to TI’s terms
and conditions of sale supplied at the time of order acknowledgment.
TI warrants performance of its hardware products to the specifications applicable at the time of sale in
accordance with TI’s standard warranty. Testing and other quality control techniques are used to the extent TI
deems necessary to support this warranty . Except where mandated by government requirements, testing of all
parameters of each product is not necessarily performed.
TI assumes no liability for applications assistance or customer product design. Customers are responsible for
their products and applications using TI components. To minimize the risks associated with customer products
and applications, customers should provide adequate design and operating safeguards.
TI does not warrant or represent that any license, either express or implied, is granted under any TI patent right,
copyright, mask work right, or other TI intellectual property right relating to any combination, machine, or process
in which TI products or services are used. Information published by TI regarding third-party products or services
does not constitute a license from TI to use such products or services or a warranty or endorsement thereof.
Use of such information may require a license from a third party under the patents or other intellectual property
of the third party, or a license from TI under the patents or other intellectual property of TI.
Reproduction of information in TI data books or data sheets is permissible only if reproduction is without
alteration and is accompanied by all associated warranties, conditions, limitations, and notices. Reproduction
of this information with alteration is an unfair and deceptive business practice. TI is not responsible or liable for
such altered documentation.
Resale of TI products or services with statements different from or beyond the parameters stated by TI for that
product or service voids all express and any implied warranties for the associated TI product or service and
is an unfair and deceptive business practice. TI is not responsible or liable for any such statements.
Following are URLs where you can obtain information on other Texas Instruments products and application
solutions:
Products Applications
Amplifiers amplifier.ti.com Audio www.ti.com/audio
Data Converters dataconverter.ti.com Automotive www.ti.com/automotive
DSP dsp.ti.com Broadband www.ti.com/broadband
Interface interface.ti.com Digital Control www.ti.com/digitalcontrol
Logic logic.ti.com Military www.ti.com/military
Power Mgmt power.ti.com Optical Networking www.ti.com/opticalnetwork
Microcontrollers microcontroller.ti.com Security www.ti.com/security
Telephony www.ti.com/telephony
Video & Imaging www .ti.com/video
Wireless www.ti.com/wireless
Mailing Address: Texas Instruments
Post Office Box 655303 Dallas, Texas 75265
Copyright 2003, Texas Instruments Incorporated
