Datasheet OPA2344EA, OPA344UA-2K5, OPA345NA-3K, OPA345UA, OPA4344UA Datasheet (Burr Brown)
...Page 1
®
®
OPA342
OPA4344
OPA344
OPA345
OPA344
OPA2344
OPA4344
OPA345
OPA2345
For most current data sheet and other product
information, visit www.burr-brown.com
OPA4345
LOW POWER, SINGLE-SUPPLY, RAIL-TO-RAIL
OPERA TIONAL AMPLIFIERS
Micro
Amplifier
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
OPA2344, OPA2345
Out A
–In A
+In A
V–
1
A
2
3
4
8
7
B
6
5
V+
Out B
–In B
+In B
Out
V–
+In
NC
–In
+In
V–
1
2
3
1
2
3
4
OPA344, OPA345
OPA344, OPA345
SOT23-5
™
Series
DESCRIPTION
The OPA344 and OPA345 series rail-to-rail CMOS
operational amplifiers are designed for precision, lowpower, 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.
V+
5
–In
4
Out A
–In A
+In A
NC
8
V+
7
Out
6
NC
5
+V
+In B
–In B
Out B
OPA4344, OPA4345
1
2
3
4
5
6
7
AD
BC
Out D
14
–In D
13
+In D
12
–V
11
+In C
10
–In C
9
Out C
8
SO-8, MSOP-8, 8-Pin DIP (OPA2344 Only)
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
© 2000 Burr-Brown Corporation PDS-1486A Printed in U.S.A. April, 2000
SO-8, 8-Pin DIP (OPA344 Only)
TSSOP-14, SO-14, 14-PIn DIP (OPA4344 Only)
Page 2
SPECIFICATIONS: VS = 2.7V to 5.5V
At TA = +25°C, RL = 10kΩ connected to VS/ 2 and V
Boldface limits apply over the temperature range, T
PARAMETER CONDITION MIN TYP MAX UNITS
OFFSET VOLTAGE
Input Offset Voltage V
Over Temperature
vs Temperature dV
vs Power Supply PSRR V
OS
/dT ±3 µV/°C
OS
Over Temperature V
Channel Separation, dc 0.2 µV/V
f = 1kHz 130 dB
INPUT BIAS CURRENT
Input Bias Current I
Over Temperature See Typical Curve pA
Input Offset Current I
OS
NOISE
Input Voltage Noise f = 0.1 to 50kHz 8 µVrms
Input Voltage Noise Density e
Current Noise Density i
INPUT VOLTAGE RANGE
Common-Mode Voltage Range V
Common-Mode Rejection Ratio CMRR V
CM
Over Temperature V
Common-Mode Rejection CMRR V
Over Temperature V
Common-Mode Rejection CMRR V
Over Temperature V
INPUT IMPEDANCE
Differential 10
Common-Mode 10
OPEN-LOOP GAIN
Open-Loop Voltage Gain A
Over Temperature R
OL
Over Temperature R
FREQUENCY RESPONSE C
Gain-Bandwidth Product GBW 1 MHz
Slew Rate SR 0.8 V/µs
Settling Time, 0.1% V
0.01% V
Overload Recovery Time V
Total Harmonic Distortion + Noise THD+N V
OUTPUT
Voltage Output Swing from Rail
(1)
Over Temperature R
Over Temperature R
Short-Circuit Current I
Capacitive Load Drive C
SC
LOAD
POWER SUPPLY
Specified Voltage Range V
Operating Voltage Range 2.5 to 5.5 V
Quiescent Current (per amplifier) I
Over Temperature 300 µA
TEMPERATURE RANGE
Specified Range –40 85 °C
Operating Range –55 125 °C
Storage Range –65 150 °C
Thermal Resistance
θ
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.
®
OPA344, 2344, 4344
OPA345, 2345, 4345
= VS/ 2, unless otherwise noted.
OUT
= –40°C to +85°C.
A
OPA344NA, UA, PA
OPA2344EA, UA, PA
OPA4344EA, UA, PA
VS = +5.5V, VCM = VS/2 ±0.2 ±1mV
±0.8 ±1.2 mV
= 2.7V to 5.5V, V
S
= 2.7V to 5.5V, V
S
B
n
n
= +5.5V, –0.3V < VCM < (V+)-1.8 76 92 dB
S
= +5.5V, –0.3V < VCM < (V+)-1.8 74 dB
S
S
S
f = 10kHz 30 nV/√Hz
f = 10kHz 0.5 fA/√Hz
= +5.5V, –0.3V < VCM < 5.8V 70 84 dB
= +5.5V, –0.3V < VCM < 5.8V 68 dB
= +2.7V, –0.3V < VCM < 3V 66 80 dB
S
= +2.7V, –0.3V < VCM < 3V 64 dB
S
RL = 100kΩ, 10mV < VO < (V+) –10mV 104 122 dB
= 100kΩ, 10mV < VO < (V+) –10mV 100 dB
L
= 5kΩ, 400mV < VO < (V+) –400mV 96 120 dB
R
L
= 5kΩ, 400mV < VO < (V+) –400mV 90 dB
L
L
= 5.5V, 2V Step 5 µs
S
= 5.5V, 2V Step 8 µs
S
= 5.5V, VO = 3Vp-p, G = 1, f = 1kHz 0.006 %
S
IN
RL = 100kΩ, AOL ≥ 96dB 1 mV
= 100kΩ, AOL ≥ 104dB 3 10 mV
R
L
= 100kΩ, AOL ≥ 100dB 10 mV
L
= 5kΩ, A
R
L
= 5kΩ, AOL ≥ 90dB 400 mV
L
S
Q
JA
VS = 5.5V, IO = 0 150 250 µA
< (V+) -1.8V 30 200 µV/V
CM
< (V+) -1.8V 250 µV/V
CM
±0.2 ±10 pA
±0.2 ±10 pA
–0.3 (V+) + 0.3 V
13
|| 3 Ω || pF
13
|| 6 Ω || pF
= 100pF
• G = V
S
≥ 96dB 40 400 mV
OL
2.5 µs
±15 mA
See Typical Curve
2.7 5.5 V
2
Page 3
SPECIFICATIONS: VS = 2.7V to 5.5V
At TA = +25°C, RL = 10kΩ connected to VS/ 2 and V
Boldface limits apply over the temperature range, T
PARAMETER CONDITION MIN TYP MAX UNITS
OFFSET VOLTAGE
Input Offset Voltage V
Over Temperature
vs Temperature dV
vs Power Supply PSRR V
OS
/dT ±3 µV/°C
OS
Over Temperature V
Channel Separation, dc 0.2 µV/V
f = 1kHz 130 dB
INPUT BIAS CURRENT
Input Bias Current I
Over Temperature See Typical Curve pA
Input Offset Current I
OS
NOISE
Input Voltage Noise f = 0.1 to 50kHz 8 µVrms
Input Voltage Noise Density e
Current Noise Density i
INPUT VOLTAGE RANGE
Common-Mode Voltage Range V
Common-Mode Rejection Ratio CMRR V
CM
Over Temperature V
Common-Mode Rejection Ratio CMRR V
Over Temperature V
Common-Mode Rejection Ratio CMRR V
Over Temperature V
INPUT IMPEDANCE
Differential 10
Common-Mode 10
OPEN-LOOP GAIN
Open-Loop Voltage Gain A
Over Temperature R
Over Temperature R
FREQUENCY RESPONSE C
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 V
Total Harmonic Distortion + Noise THD+N V
OUTPUT
Voltage Output Swing from Rail
(1)
Over Temperature R
Over Temperature R
Short-Circuit Current I
Capacitive Load Drive C
SC
LOAD
POWER SUPPLY
Specified Voltage Range V
Operating Voltage Range 2.5 to 5.5 V
Quiescent Current (per amplifier) I
Over Temperature 300 µA
TEMPERATURE RANGE
Specified Range –40 85 °C
Operating Range –55 125 °C
Storage Range –65 150 °C
Thermal Resistance
θ
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.
= VS/2, unless otherwise noted.
OUT
= –40°C to +85°C.
A
OPA345NA, UA
OPA2345EA, UA
OPA4345EA, UA
VS = +5.5V, VCM = VS/2 ±0.2 ±1mV
±0.8 ±1.2 mV
= 2.7V to 5.5V, V
S
= 2.7V to 5.5V, V
S
B
n
n
= +5.5V, –0.3V < VCM < (V+)-1.8 76 92 dB
S
= +5.5V, –0.3V < VCM < (V+)-1.8 74 dB
S
S
S
RL = 100kΩ, 10mV < VO < (V+) –10mV 104 122 dB
OL
= 100kΩ, 10mV < VO < (V+) –10mV 100 dB
L
= 5kΩ, 400mV < VO < (V+) –400mV 96 120 dB
R
L
= 5kΩ, 400mV < VO < (V+) –400mV 90 dB
L
= 5.5V, VO = 2.5Vp-p, G = 5, f = 1kHz 0.006 %
S
f = 10kHz 30 nV/√Hz
f = 10kHz 0.5 fA/√Hz
= +5.5V, –0.3V < VCM < 5.8V 70 84 dB
= +5.5V, –0.3V < VCM < 5.8V 68 dB
= +2.7V, –0.3V < VCM < 3V 66 80 dB
S
= +2.7V, –0.3V < VCM < 3V 64 dB
S
L
IN
RL = 100kΩ, AOL ≥ 96dB 1 mV
= 100kΩ, AOL ≥ 104dB 3 10 mV
R
L
= 100kΩ, AOL ≥ 100dB 10 mV
L
= 5kΩ, A
R
L
= 5kΩ, AOL ≥ 90dB 400 mV
L
S
Q
JA
VS = 5.5V, IO = 0 150 250 µA
< (V+) -1.8V 30 200 µV/V
CM
< (V+) -1.8V 250 µV/V
CM
±0.2 ±10 pA
±0.2 ±10 pA
–0.3 (V+) + 0.3 V
13
|| 3 Ω || pF
13
|| 6 Ω || pF
= 100pF
• G = V
S
≥ 96dB 40 400 mV
OL
2.5 µs
±15 mA
See Typical Curve
2.7 5.5 V
3
OPA345, 2345, 4345
OPA344, 2344, 4344
®
Page 4
ABSOLUTE MAXIMUM RATINGS
Supply Voltage, V+ to V- ................................................................... 7.5V
Signal Input Terminals, Voltage
Output Short-Circuit
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 operation 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.
(3)
(2)
..................... (V–) –0.5V to (V+) +0.5V
(2)
Current
.............................................................. Continuous
.................................................... 10mA
(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.
PACKAGE/ORDERING INFORMATION
PACKAGE SPECIFIED
PRODUCT PACKAGE NUMBER RANGE MARKING NUMBER
DRAWING TEMPERATURE PACKAGE ORDERING TRANSPORT
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.
(1)
MEDIA
®
OPA344, 2344, 4344
OPA345, 2345, 4345
4
Page 5
TYPICAL PERFORMANCE CURVES
MAXIMUM OUTPUT VOLTAGE vs FREQUENCY
100k
Maximum Output Voltage (Vp-p)
Frequency (Hz)
1M 10M
6
5
4
3
2
1
0
OPA344
VS = +2.7V
VS = +5.5V
VS =
+5V
OPA345
At TA = +25°C, VS = +5V, and RL = 10kΩ connected to VS/2, unless otherwise noted.
120
100
80
60
Gain (dB)
40
20
0
0.1 1
100
80
60
OPEN-LOOP GAIN/PHASE vs FREQUENCY
OPA344
Gain
10 100 1k 10k 100k 1M 10M
Frequency (Hz)
POWER SUPPLY AND COMMON-MODE
REJECTION RATIO vs FREQUENCY
+PSRR
CMRR
–PSRR
Phase
0
30
60
90
120
150
180
120
100
80
60
Phase (°)
Gain (dB)
40
20
0
OPEN-LOOP GAIN/PHASE vs FREQUENCY
OPA345
Gain
0.1 1
10 100 1k 10k 100k 1M 10M
Frequency (Hz)
Phase
0
30
60
90
120
150
180
Phase (°)
40
Rejection Ratio (dB)
20
10
10
140
120
100
80
Channel Separation (dB)
60
100
CHANNEL SEPARATION vs FREQUENCY
Dual and quad devices.
G = 1, all channels.
Quad measured channel
A to D or B to C—other
combinations yield improved
rejection.
100 1k 10k 100k
Frequency (Hz)
1k 10k 100k 1M
Frequency (Hz)
10000
Voltage Noise (nV/√Hz)
1000
100
VOLTAGE AND CURRENT NOISE
SPECTRAL DENSITY vs FREQUENCY
I
N
V
N
10
1
10 100 1k 10k 100k 1M 10M
Frequency (Hz)
100
10
1
Current Noise (fA/√Hz)
0.1
5
OPA345, 2345, 4345
OPA344, 2344, 4344
®
Page 6
TYPICAL PERFORMANCE CUR VES (Cont.)
At TA = +25°C, VS = +5V, and RL = 10kΩ connected to VS/2, unless otherwise noted.
TOTAL HARMONIC DISTORTION + NOISE
1
OPA344: G = 1
OPA345: G = 5
0.1
THD+N (%)
0.010
0.001
20
INPUT BIAS CURRENT vs TEMPERATURE
10000
1000
100
10
Input Bias Current (pA)
1
0.1
–75
vs FREQUENCY
100 1k 10k 20k
Frequency (Hz)
–25 0 25–50 10050 75 125
Temperature (°C)
OPEN-LOOP GAIN, COMMON-MODE REJECTION RATIO,
AND POWER-SUPPLY REJECTION vs TEMPERATURE
140
120
100
80
60
, CMRR, PSRR (dB)
40
OL
A
20
0
–75
200
175
150
135
100
75
50
Quiescent Current (µA)
25
SHORT-CIRCUIT CURRENT vs TEMPERATURE
0
–75 –50 0
–25 0 25–50 50 12575 100
QUIESCENT CURRENT AND
A
PSRR
Temperature (°C)
+I
SC
–I
SC
Temperature (°C)
OL
I
Q
25 50 100
CMRR
75–25 125
40
35
30
25
20
15
10
Short-Circuit Current (mA)
5
0
3.0
2.5
2.0
1.5
1.0
Slew Rate (V/µs)
0.5
0
–75
SLEW RATE vs TEMPERATURE
OPA345
250
Temperature (°C)
®
OPA344, 2344, 4344
OPA345, 2345, 4345
OPA344
SR–
SR+
SR–
SR+
7550–25–50 125100
6
6
4
2
0
–2
Input Bias Current (pA)
–4
–6
012 4356
–1
INPUT BIAS CURRENT
vs COMMON-MODE VOLTAGE
V–
Supply
Input voltage ≤ –0.3V
can cause op amp output
to lock up. See text.
Common-Mode Voltage (V)
V+
Supply
Page 7
TYPICAL PERFORMANCE CUR VES (Cont.)
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
OFFSET VOLTAGE
PRODUCTION DISTRIBUTION
Population
Offset Voltage (µV)
–1000
–800
–600
–400
–200
0
200
400
600
800
1000
At TA = +25°C, VS = +5V, and RL = 10kΩ connected to VS/2, unless otherwise noted.
SHORT-CIRCUIT CURRENT vs SUPPLY VOLTAGE
160
155
150
145
Quiescent Current (µA)
140
23456
140
130
OPEN-LOOP GAIN vs OUTPUT VOLTAGE SWING
QUIESCENT CURRENT AND
+I
SC
–I
SC
I
Q
Supply Voltage (V)
RL = 100kΩ
20
15
10
5
Short-Circuit Current (mA)
0
120
110
Open-Loop Gain (dB)
100
120 100 80 60 40 20 0
Output Voltage Swing from Rail (mV)
Population
–10
–8
RL = 5kΩ
OFFSET VOLTAGE DRIFT
PRODUCTION DISTRIBUTION
–6
–4
Offset Voltage Drift (µV/°C)
0
2
–2
4
QUIESCENT CURRENT
PRODUCTION DISTRIBUTION
Population
6
8
10
100
115
130
145
160
Quiescent Current (µA)
175
190
205
220
235
250
7
OPA345, 2345, 4345
OPA344, 2344, 4344
®
Page 8
TYPICAL PERFORMANCE CUR VES (Cont.)
At TA = +25°C, VS = +5V, and RL = 10kΩ connected to VS/2, unless otherwise noted.
SMALL-SIGNAL OVERSHOOT vs LOAD CAPACITANCE
50
OPA344
45
40
35
30
25
20
15
10
Small-Signal Overshoot (%)
5
0
1
LARGE-SIGNAL STEP RESPONSE: OPA344
G = +1
G = –1
10 100 1k 10k
Load Capacitance (pF)
G = +1, R
= 10kΩ, CL = 100pF
L
G = +5
G = –5
OPA344
SMALL-SIGNAL OVERSHOOT vs LOAD CAPACITANCE
70
OPA345
60
50
40
30
20
Small-Signal Overshoot (%)
10
0
LARGE-SIGNAL STEP RESPONSE: OPA345
G = +5
100 1k 10k10
Load Capacitance (pF)
G = +5, R
= 10kΩ, CL = 100pF
L
G = –5
G = –10, +10
OPA345
1V/div
5µs/div
SMALL-SIGNAL STEP RESPONSE: OPA344
G = +1, R
20mV/div
= 10kΩ, CL = 100pF
L
5µs/div
OPA344
1V/div
5µs/div
SMALL-SIGNAL STEP RESPONSE: OPA345
G = +5, R
20mV/div
= 10kΩ, CL = 100pF
L
5µs/div
OPA345
®
OPA344, 2344, 4344
OPA345, 2345, 4345
8
Page 9
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.
Input
5V
1V/div
0V
Output (inverted on scope)
5µs/div
G = +1, VS = +5V
OPERATING VOLTAGE
OPA344 and OPA345 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 OPA344 and
OPA345 series extends 300mV beyond the supply rails.
This is achieved with a complementary input stage—an Nchannel 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 Pchannel 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 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.”
FIGURE 1. Rail-to-Rail Input and Output.
V+
Reference
Current
VIN+
VIN–
V
V
BIAS1
BIAS2
Class AB
Control
Circuitry
V
O
V–
(Ground)
FIGURE 2. Simplified Schematic.
9
OPA345, 2345, 4345
OPA344, 2344, 4344
®
Page 10
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, however, applications using these special double-input-stage
op amps may benefit from consideration of their special
behavior.
In many applications, operation remains within the common-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-
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 amplifier 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 configuration can still produce a rail-to-rail output.
Inverting amplifiers have a constant common-mode voltage equal to VB. If this bias voltage is constant, no
discontinuity will be created. The bias voltage can generally be chosen to avoid the transition region.
tion, signal levels and biasing can often avoid this transition region.
V
B
Non-Inverting Gain
V+
V
IN
= V
V
CM
IN
V
IN
G = 1 Buffer
V+
= VIN = V
V
CM
V
O
O
FIGURE 3. Design Optimization with Rail-to-Rail Input Op Amps.
Inverting Amplifier
V
IN
V
O
V
V+
V
O
B
= V
V
CM
B
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 capability 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 sufficiently negative, the op amp output may lock up in an
inoperative state. A Schottky diode clamp circuit will prevent this—see Figure 4. The series resistor prevents excessive 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.
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.”
V+
I
OVERLOAD
V
IN
10mA max
1kΩ
OPA344
IN5818
Schottky diode is required only
if input voltage can go more
than 0.3V below ground.
V
OUT
FIGURE 4. Input Current Protection for Voltages Exceed-
ing the Supply Voltage.
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
®
OPA344, 2344, 4344
OPA345, 2345, 4345
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
10
Page 11
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 performance 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.
V+
R
V
IN
OPA344
S
10Ω to
20Ω
R
L
V
OUT
C
L
FIGURE 5. Series Resistor in Unity-Gain Configuration
Improves Capacitive Load Drive.
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, lowpower 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.
+5V
8
V
IN
VIN = 0V to 5V for
0V to 5V output.
OPA344
500Ω
3300pF
RC network filters high frequency noise.
+In
ADS7822
12-Bit A/D
2
–In
3
FIGURE 6. OPA344 in Noninverting Configuration Driving ADS7822.
V+ = +2.7V to 5V
R
R
1
1.5kΩ
Electret
Microphone
NOTE: (1) Electret microphone
powered by R
(1)
1
.
R
1MΩ
C
1
1000pF
R
1MΩ
2
3
R
4
20kΩ
OPA2344
R
5
20kΩ
1/2
R
100kΩ
R
7
51kΩ
6
G = 100
R
150kΩ
1000pF
C
2
510kΩ
C
33pF
8
1/2
OPA2344
0.1µF 0.1µF
1
V+
4GND
V
REF
DCLOCK
D
OUT
CS/SHDN
NOTE: A/D Input = 0 to V
Passband 300Hz to 3kHz
9
3
1
V
REF
+IN
2
–IN
ADS7822
12-Bit A/D
3
7
6
5
V
+
8
7
6
5
4
GND
Interface
DCLOCK
D
OUT
CS/SHDN
Serial
REF
Serial
Interface
FIGURE 7. Speech Bandpass Filtered Data Acquisition System.
11
OPA344, 2344, 4344
OPA345, 2345, 4345
®
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