TI OPA211

OPA211
OPA2211
OP
A2
11
OP
A2
11
OP
A2
11
OPA
2211
OP
A2
211
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SBOS377D – OCTOBER 2006 – REVISED FEBRUARY 2008
1.1nV/√Hz Noise, Low Power, Precision
Operational Amplifier in Small DFN-8 Package
• LOW VOLTAGE NOISE: 1.1nV/√Hz at 1kHz
• INPUT VOLTAGE NOISE:
80nVPP (0.1Hz to 10Hz)
• THD+N: –136dB (G = 1, f = 1kHz)
• OFFSET VOLTAGE: 125µV (max)
• OFFSET VOLTAGE DRIFT: 0.35µV/°C (typ)
• LOW SUPPLY CURRENT: 3.6mA/Ch (typ)
• UNITY GAIN STABLE
• GAIN BANDWIDTH PRODUCT:
80MHz (G = 100)
45MHz (G = 1)
• SLEW RATE: 27V/µs
• 16-BIT SETTLING: 700ns
• WIDE SUPPLY RANGE:
±2.25V to ±18V, +4.5V to +36V
• RAIL-TO-RAIL OUTPUT
• OUTPUT CURRENT: 30mA
• DFN-8 (3×3mm), MSOP-8, AND SO-8
23
APPLICATIONS
•
•
•
•
•
•
•
•
•
•
•
•
•
PLL LOOP FILTER
LOW-NOISE, LOW-POWER SIGNAL
PROCESSING
16-BIT ADC DRIVERS
DAC OUTPUT AMPLIFIER
ACTIVE FILTERS
LOW-NOISE INSTRUMENTATION AMPS
ULTRASOUND AMPLIFIERS
PROFESSIONAL AUDIO PREAMPLIFIERS
LOW-NOISE FREQUENCY SYNTHESIZERS
INFRARED DETECTOR AMPLIFIERS
HYDROPHONE AMPLIFIERS
GEOPHONE AMPLIFIERS
MEDICAL
DESCRIPTION
The OPA211 series of precision operational
amplifiers achieves very low 1.1nV/√Hz noise density
with a supply current of only 3.6mA. This series also
offers rail-to-rail output swing, which maximizes
dynamic range.
The extremely low voltage and low current noise,
high speed, and wide output swing of the OPA211
series make these devices an excellent choice as a
loop filter amplifier in PLL applications.
In precision data acquisition applications, the
OPA211 series of op amps provides 700ns settling
time to 16-bit accuracy throughout 10V output swings.
This ac performance, combined with only 125µV of
offset and 0.35µV/°C of drift over temperature, makes
the OPA211 ideal for driving high-precision 16-bit
analog-to-digital converters (ADCs) or buffering the
output of high-resolution digital-to-analog converters
(DACs).
The OPA211 series is specified over a wide
dual-power supply range of ±2.25V to ±18V, or
single-supply operation from +4.5V to +36V.
The OPA211 is available in the small DFN-8
(3×3mm), MSOP-8, and SO-8 packages. A dual
version, the OPA2211, is available in the DFN-8
(3×3mm) or an SO-8 PowerPAD™ package. This
series of op amps is specified from TA = –40°C to
+125°C.
INPUT VOLTAGE NOISE DENSITY vs FREQUENCY
100
Voltage Noise Density (nV/ÖHz)
FEATURES
1
10
1
0.1
1
10
100
1k
10k
100k
Frequency (Hz)
1
2
3
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
PowerPAD is a trademark of Texas Instruments.
All other trademarks are the property of their respective owners.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2006–2008, Texas Instruments Incorporated
OPA211
OPA2211
www.ti.com
SBOS377D – OCTOBER 2006 – REVISED FEBRUARY 2008
This integrated circuit can be damaged by ESD. Texas Instruments 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.
ABSOLUTE MAXIMUM RATINGS (1)
Over operating free-air temperature range (unless otherwise noted).
Supply Voltage
VALUE
UNIT
40
V
VS = (V+) – (V–)
Input Voltage
(V–) – 0.5 to (V+) + 0.5
V
±10
mA
Input Current (Any pin except power-supply pins)
Output Short-Circuit (2)
Continuous
Operating Temperature
(TA)
–55 to +150
°C
Storage Temperature
(TA)
–65 to +150
°C
Junction Temperature
(TJ)
200
°C
Human Body Model (HBM)
3000
V
Charged Device Model (CDM)
1000
V
ESD Ratings
(1)
(2)
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, and functional operation of the device at these or any other conditions beyond
those specified is not supported.
Short-circuit to VS/2 (ground in symmetrical dual supply setups), one amplifier per package.
PACKAGE/ORDERING INFORMATION (1)
PRODUCT
PACKAGE
DESIGNATOR
PACKAGE
MARKING
ü
DRG
OBDQ
ü
DGK
OBCQ
D
A TI OPA
211
PACKAGE-LEAD
SINGLE
SHUTDOWN
DFN-8 (3×3mm) (2)
ü
MSOP-8 (2)
ü
DUAL
Standard Grade
OPA211AI
OPA211AI
ü
SO-8
DFN-8 (3×3mm) (3)
OPA2211AI
SO-8 PowerPAD
ü
(3)
ü
DRG
OBHQ
DDA
A TI OPA
2211
High Grade (3)
OPA211I
OPA2211I
(1)
(2)
(3)
2
DFN-8 (3×3mm)
ü
ü
DRG
OBDQ
MSOP-8
ü
ü
DGK
OBCQ
SO-8
ü
D
TI OPA
211
DFN-8 (3×3mm)
ü
DRG
OBHQ
SO-8 PowerPAD
ü
DDA
TI OPA
2211
For the most current package and ordering information see the Package Option Addendum at the end of this document, or see the TI
web site at www.ti.com.
Available Q2, 2008.
Available Q3, 2008.
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Copyright © 2006–2008, Texas Instruments Incorporated
Product Folder Link(s): OPA211 OPA2211
OPA211
OPA2211
www.ti.com
SBOS377D – OCTOBER 2006 – REVISED FEBRUARY 2008
PIN CONFIGURATIONS
OPA211
SO-8
NC
(1)
OPA211
MSOP-8(4)
(1)
1
8
NC
-IN
2
7
V+
+IN
3
6
OUT
V-
4
5
NC
NC
(1)
1
8
Shutdown
-IN
2
7
V+
+IN
3
6
OUT
V-
4
5
NC
(1)
OPA211(4)
DFN-8 (3×3mm)
NC
(1)
1
-IN 2
+IN 3
V- 4
Pad
(1)
OPA2211
DFN-8 (3×3mm)(5)
8 Shutdown
(3)
8 V+
OUT A 1
7 V+
-IN A 2
6 OUT
5 NC
(3)
+IN A 3
(1)
V- 4
(2)
Pad
7 OUT B
A
B
6 -IN B
5 +IN B
(2)
OPA2211
SO-8 PowerPAD(5)
OUT A
1
-IN A
2
+IN A
3
V-
4
Pad
A
B
8
V+
7
OUT B
6
-IN B
5
+IN B
(2)
(1)
NC denotes no internal connection. Pin can be left floating or connected to any voltage between (V–) and (V+).
(2)
Exposed thermal die pad on underside; connect thermal die pad to V–.
(3)
Shutdown function:
•
Device enabled: (V–) ≤ VSHUTDOWN ≤ (V+) – 3V
•
Device disabled: VSHUTDOWN ≥ (V+) – 0.35V
(4)
Available Q2, 2008.
(5)
Available Q3, 2008.
Copyright © 2006–2008, Texas Instruments Incorporated
Product Folder Link(s): OPA211 OPA2211
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3
OPA211
OPA2211
www.ti.com
SBOS377D – OCTOBER 2006 – REVISED FEBRUARY 2008
ELECTRICAL CHARACTERISTICS: VS = ±2.25V to ±18V
BOLDFACE limits apply over the specified temperature range, TA = –40°C to +125°C.
At TA = +25°C and RL = 10kΩ, unless otherwise noted.
Standard Grade
OPA211A, OPA2211A
PARAMETER
CONDITIONS
MIN
TYP
MAX
±30
±125
UNIT
OFFSET VOLTAGE
Input Offset Voltage
Drift
VOS
VS = ±15V
dVOS/dT
vs Power Supply
PSRR
VS = ±2.25V to ±18V
0.1
Over Temperature
µV
µV/°C
0.35
1
µV/V
3
µV/V
INPUT BIAS CURRENT
Input Bias Current
IB
VCM = 0V
±60
Over Temperature
Offset Current
IOS
VCM = 0V
±25
Over Temperature
±175
nA
±200
nA
±100
nA
±150
nA
NOISE
Input Voltage Noise
en
Input Voltage Noise Density
Input Current Noise Density
in
f = 0.1Hz to 10Hz
80
nVPP
f = 10Hz
2
nV/√Hz
f = 100Hz
1.4
nV/√Hz
f = 1kHz
1.1
nV/√Hz
f = 10Hz
3.2
pA/√Hz
f = 1kHz
1.7
pA/√Hz
INPUT VOLTAGE RANGE
VS ≥ ±5V
(V–) + 1.8
(V+) – 1.4
VS < ±5V
(V–) + 2
(V+) – 1.4
VS ≥ ±5V, (V–) + 2V ≤ VCM ≤ (V+) – 2V
114
120
dB
VS < ±5V, (V–) + 2V ≤ VCM ≤ (V+) – 2V
110
120
dB
Differential
20k || 8
Ω || pF
Common-Mode
109 || 2
Ω || pF
Common-Mode Voltage Range
Common-Mode Rejection Ratio
VCM
CMRR
V
V
INPUT IMPEDANCE
OPEN-LOOP GAIN
Open-Loop Voltage Gain
Over Temperature
AOL
(V–) + 0.2V ≤ VO ≤ (V+) – 0.2V,
RL = 10kΩ
114
130
dB
AOL
(V–) + 0.6V ≤ VO ≤ (V+) – 0.6V,
RL = 600Ω
110
114
dB
AOL
(V–) + 0.6V ≤ VO ≤ (V+) – 0.6V,
IO ≤ 15mA
110
dB
AOL
(V–) + 0.6V ≤ VO ≤ (V+)–0.6V
15mA ≤ IO ≤ 30mA
103
dB
FREQUENCY RESPONSE
Gain-Bandwidth Product
G = 100
80
MHz
G=1
45
MHz
27
V/µs
VS = ±15V, G = –1, 10V Step, CL = 100pF
400
ns
0.0015% (16-bit)
VS = ±15V, G = –1, 10V Step, CL = 100pF
700
ns
Overload Recovery Time
G = –10
500
ns
G = +1, f = 1kHz,
VO = 3VRMS, RL = 600Ω
0.000015
%
–136
dB
Slew Rate
SR
Settling Time, 0.01%
Total Harmonic Distortion + Noise
4
GBW
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tS
THD+N
Copyright © 2006–2008, Texas Instruments Incorporated
Product Folder Link(s): OPA211 OPA2211
OPA211
OPA2211
www.ti.com
SBOS377D – OCTOBER 2006 – REVISED FEBRUARY 2008
ELECTRICAL CHARACTERISTICS: VS = ±2.25V to ±18V (continued)
BOLDFACE limits apply over the specified temperature range, TA = –40°C to +125°C.
At TA = +25°C and RL = 10kΩ, unless otherwise noted.
Standard Grade
OPA211A, OPA2211A
PARAMETER
CONDITIONS
MIN
RL = 10kΩ, AOL ≥ 114dB
RL = 600Ω, AOL ≥ 110dB
IO < 25mA, AOL ≥ 110dB
TYP
MAX
UNIT
(V–) + 0.2
(V+) – 0.2
V
(V–) + 0.6
(V+) – 0.6
V
(V–) + 0.6
(V+) – 0.6
OUTPUT
Voltage Output
Short-Circuit Current
Capacitive Load Drive
Open-Loop Output Impedance
VOUT
ISC
CLOAD
ZO
V
+30/–45
mA
See Typical Characteristics
pF
5
Ω
1MHz
SHUTDOWN
Shutdown Pin Input Voltage
Device shutdown
(V+) – 0.35
V
Device enabled
(V+) – 3
V
POWER SUPPLY
Specified Voltage
VS
Quiescent Current
(per channel)
IQ
±2.25
IOUT = 0A
3.6
Over Temperature
±18
V
4.5
mA
6
mA
TEMPERATURE RANGE
Specified Range
TA
–40
+125
°C
Operating Range
TA
–55
+150
°C
Thermal Resistance
DFN (3mm × 3mm)
Soldered to approximately
5cm × 5cm copper area
θ JA
65
°C/W
θ JC
57
°C/W
MSOP-8
θ JA
200
°C/W
SO-8
θ JA
150
°C/W
52
°C/W
43
°C/W
SO-8 PowerPAD
Test board 1in × 0.5in heat-spreader,
1oz copper
θ JA
θ JC
Copyright © 2006–2008, Texas Instruments Incorporated
Product Folder Link(s): OPA211 OPA2211
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OPA211
OPA2211
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SBOS377D – OCTOBER 2006 – REVISED FEBRUARY 2008
TYPICAL CHARACTERISTICS
At TA = +25°C, VS = ±18V, and RL = 10kΩ, unless otherwise noted.
INPUT VOLTAGE NOISE DENSITY
vs FREQUENCY
INPUT CURRENT NOISE DENSITY
vs FREQUENCY
100
Current Noise Density (pA/ÖHz)
Voltage Noise Density (nV/ÖHz)
100
10
10
1
1
0.1
1
10
100
1k
10k
1
0.1
100k
10
Frequency (Hz)
Figure 1.
G=1
VOUT = 3VRMS
0.00001
-140
10k 20k
1
Total Harmonic Distortion + Noise (%)
Total Harmonic Distortion + Noise (%)
G = 11
VOUT = 3VRMS
1k
100k
0.1
-40
VS = ±15V
RL = 600W
1kHz Signal
-60
0.01
-80
G = 11
G=1
0.001
-100
0.0001
-120
0.00001
0.01
Total Harmonic Distortion + Noise (dB)
-120
Total Harmonic Distortion + Noise (dB)
0.0001
100
10k
THD+N RATIO vs AMPLITUDE
-100
VS = ±15V
RL = 600W
10
1k
Figure 2.
THD+N RATIO vs FREQUENCY
0.001
100
Frequency (Hz)
-140
0.1
1
10
100
Amplitude (VRMS)
Frequency (Hz)
Figure 3.
Figure 4.
20nV/div
0.1Hz TO 10Hz NOISE
Time (1s/div)
Figure 5.
6
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Product Folder Link(s): OPA211 OPA2211
OPA211
OPA2211
www.ti.com
SBOS377D – OCTOBER 2006 – REVISED FEBRUARY 2008
TYPICAL CHARACTERISTICS (continued)
At TA = +25°C, VS = ±18V, and RL = 10kΩ, unless otherwise noted.
POWER-SUPPLY REJECTION RATIO
vs FREQUENCY (Referred to Input)
COMMON-MODE REJECTION RATIO
vs FREQUENCY
160
140
140
120
100
CMRR (dB)
PSRR (dB)
120
100
-PSRR
80
+PSRR
60
80
60
40
40
20
20
0
0
1
10
100
1k
10k
100k
1M
10M
100M
100k
10k
10M
1M
100M
Frequency (Hz)
Frequency (Hz)
Figure 6.
Figure 7.
OPEN-LOOP OUTPUT IMPEDANCE
vs FREQUENCY
GAIN AND PHASE vs FREQUENCY
140
10k
180
120
Gain (dB)
100
100
10
80
60
90
40
Gain
20
1
135
Phase
Phase (°)
ZO (W)
1k
45
0
0.1
-20
10
100
1k
10k
1M
100k
10M
100
100M
1k
10k
100k
1M
10M
0
100M
Frequency (Hz)
Frequency (Hz)
Figure 8.
Figure 9.
OPEN-LOOP GAIN vs TEMPERATURE
5
Open-Loop Gain (mV/V)
4
RL = 10kW
3
2
300mV Swing From Rails
1
0
-1
200mV Swing From Rails
-2
-3
-4
-5
-75 -50 -25
0
25
50
75 100 125 150 175 200
Temperature (°C)
Figure 10.
Copyright © 2006–2008, Texas Instruments Incorporated
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OPA211
OPA2211
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SBOS377D – OCTOBER 2006 – REVISED FEBRUARY 2008
TYPICAL CHARACTERISTICS (continued)
At TA = +25°C, VS = ±18V, and RL = 10kΩ, unless otherwise noted.
OFFSET VOLTAGE DRIFT PRODUCTION DISTRIBUTION
112.5
125.0
87.5
100.0
62.5
75.0
37.5
50.0
25.0
0
12.5
-12.5
-37.5
-25.0
-62.5
-50.0
-87.5
-75.0
-112.5
-100.0
-125.0
Population
Population
OFFSET VOLTAGE PRODUCTION DISTRIBUTION
0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5
Offset Voltage Drift (mV/°C)
Offset Voltage (mV)
Figure 11.
Figure 12.
OFFSET VOLTAGE vs COMMON-MODE VOLTAGE
VOS WARMUP
12
10
2000
1500
8
6
VOS Shift (mV)
1000
500
VOS (mV)
20 Typical Units Shown
0
-500
4
2
0
-2
-4
-6
-8
-1000
-1500
-10
-12
-2000
(V-)+1.0 (V-)+1.5 (V-)+2.0
10
0
(V+)-1.5 (V+)-1.0 (V+)-0.5
20
30
VCM (V)
100
80
50
60
Figure 13.
Figure 14.
INPUT OFFSET CURRENT vs SUPPLY VOLTAGE
INPUT OFFSET CURRENT vs COMMON-MODE VOLTAGE
100
5 Typical Units Shown
VS = 36V
3 Typical Units Shown
75
60
50
40
20
IOS (nA)
IOS (nA)
40
Time (s)
0
-20
25
0
-25
Common-Mode Range
-40
-50
-60
-75
-80
-100
2.25
-100
4
6
8
10
12
14
16
18
1
5
10
Figure 15.
8
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15
20
25
30
35
VCM (V)
VS (±V)
Figure 16.
Copyright © 2006–2008, Texas Instruments Incorporated
Product Folder Link(s): OPA211 OPA2211
OPA211
OPA2211
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SBOS377D – OCTOBER 2006 – REVISED FEBRUARY 2008
TYPICAL CHARACTERISTICS (continued)
At TA = +25°C, VS = ±18V, and RL = 10kΩ, unless otherwise noted.
INPUT BIAS CURRENT vs SUPPLY VOLTAGE
INPUT BIAS CURRENT vs COMMON-MODE VOLTAGE
150
150
3 Typical Units Shown
100
Unit 1
-IB
+IB
Unit 2
50
IB (nA)
50
IB (nA)
VS = 36V
3 Typical Units Shown
100
0
Unit 2
Unit 1
0
Unit 3
-50
-50
Unit 3
-100
-IB
-100
Common-Mode Range
+IB
-150
2.25
-150
4
6
8
10
12
14
16
1
18
5
10
15
20
25
30
35
VCM (V)
VS (±V)
Figure 17.
Figure 18.
QUIESCENT CURRENT vs TEMPERATURE
QUIESCENT CURRENT vs SUPPLY VOLTAGE
6
4.0
3.5
5
3.0
2.5
IQ (mA)
IQ (mA)
4
3
2.0
1.5
2
1.0
1
0.5
0
0
-75 -50 -25
0
25
50
0
75 100 125 150 175 200
4
8
12
Figure 19.
28
32
36
SHORT-CIRCUIT CURRENT vs TEMPERATURE
0.05
0
ISC (mA)
-0.05
IQ Shift (mA)
24
Figure 20.
NORMALIZED QUIESCENT CURRENT
vs TIME
-0.10
-0.15
-0.20
-0.25
Average of 10 Typical Units
60
50
40
30
20
10
0
-10
-20
-30
-40
-50
Sourcing
Sinking
-60
-0.30
60
20
VS (V)
Temperature (°C)
0
16
120 180 240 300 360 420 480 540
600
-75 -50 -25
0
25
50
75
100 125 150 175 200
Temperature (°C)
Time (s)
Figure 21.
Figure 22.
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OPA2211
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SBOS377D – OCTOBER 2006 – REVISED FEBRUARY 2008
TYPICAL CHARACTERISTICS (continued)
At TA = +25°C, VS = ±18V, and RL = 10kΩ, unless otherwise noted.
SMALL-SIGNAL STEP RESPONSE
(100mV)
SMALL-SIGNAL STEP RESPONSE
(100mV)
G = -1
RL = 600W
CL = 100pF
CF
5.6pF
CF
5.6pF
20mV/div
20mV/div
G = -1
RL = 600W
CL = 10pF
RF
604W
RI
604W
RF
604W
RI
604W
+18V
+18V
OPA211
OPA211
CL
RL
CL
RL
-18V
-18V
Time (0.1ms/div)
Time (0.1ms/div)
Figure 23.
Figure 24.
SMALL-SIGNAL STEP RESPONSE
(100mV)
SMALL-SIGNAL STEP RESPONSE
(100mV)
G = +1
RL = 600W
CL = 100pF
20mV/div
20mV/div
G = +1
RL = 600W
CL = 10pF
+18V
OPA211
-18V
RL
+18V
OPA211
-18V
CL
RL
Time (0.1ms/div)
Time (0.1ms/div)
Figure 25.
Figure 26.
CL
SMALL-SIGNAL OVERSHOOT
vs CAPACITIVE LOAD (100mV Output Step)
60
G = +1
Overshoot (%)
50
40
G = -1
30
G = 10
20
10
0
0
200
400
600
800
1000
1200
1400
Capacitive Load (pF)
Figure 27.
10
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SBOS377D – OCTOBER 2006 – REVISED FEBRUARY 2008
TYPICAL CHARACTERISTICS (continued)
At TA = +25°C, VS = ±18V, and RL = 10kΩ, unless otherwise noted.
LARGE-SIGNAL STEP RESPONSE
LARGE-SIGNAL STEP RESPONSE
G = -1
CL = 100pF
RL = 600W
G = +1
CL = 100pF
RL = 600W
RF = 100W
2V/div
2V/div
RF = 0W
Note: See the
Applications Information
section, Input Protection.
Figure 29.
LARGE-SIGNAL POSITIVE SETTLING TIME
(10VPP, CL = 100pF)
LARGE-SIGNAL POSITIVE SETTLING TIME
(10VPP, CL = 10pF)
1.0
0.010
0.008
0.8
0.008
0.6
0.006
0.6
0.006
0.4
0.004
0.4
0.004
0.2
0.002
16-Bit
Settling
0
-0.2
0
-0.002
(±0.0015%)
-0.4
-0.004
-0.2
0
-0.002
(±0.0015%)
-0.4
-0.004
-0.006
-0.8
-0.008
-0.010
700 800 900 1000
-1.0
-0.8
-1.0
400 500 600
Time (ns)
0.002
16-Bit
Settling
0
-0.008
-0.006
200 300
0.2
-0.6
-0.6
100
D From Final Value (mV)
0.010
0.8
0
100
200 300
400 500 600
Time (ns)
-0.010
700 800 900 1000
Figure 30.
Figure 31.
LARGE-SIGNAL NEGATIVE SETTLING TIME
(10VPP, CL = 100pF)
LARGE-SIGNAL NEGATIVE SETTLING TIME
(10VPP, CL = 10pF)
0.010
0.8
0.008
0.6
0.006
0.6
0.006
0.4
0.004
0.4
0.004
0.2
0.002
16-Bit
Settling
-0.2
0
-0.002
(±0.0015%)
-0.4
-0.004
-0.6
-0.006
-0.8
-1.0
0
100
200 300
400 500 600
Time (ns)
D From Final Value (mV)
1.0
0.008
0.2
0.002
16-Bit
Settling
0
-0.2
0
-0.002
(±0.0015%)
-0.4
-0.004
-0.6
-0.006
-0.008
-0.8
-0.008
-0.010
700 800 900 1000
-1.0
0
100
200 300
Figure 32.
400 500 600
Time (ns)
D From Final Value (%)
0.010
0.8
D From Final Value (%)
1.0
0
D From Final Value (%)
1.0
0
D From Final Value (mV)
Time (0.5ms/div)
Figure 28.
D From Final Value (%)
D From Final Value (mV)
Time (0.5ms/div)
-0.010
700 800 900 1000
Figure 33.
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TYPICAL CHARACTERISTICS (continued)
At TA = +25°C, VS = ±18V, and RL = 10kΩ, unless otherwise noted.
NEGATIVE OVERLOAD RECOVERY
POSITIVE OVERLOAD RECOVERY
G = -10
VIN
G = -10
10kW
VOUT
1kW
0V
OPA211
VIN
5V/div
5V/div
10kW
1kW
OPA211
VOUT
VOUT
VIN
0V
VOUT
VIN
Time (0.5ms/div)
Time (0.5ms/div)
Figure 34.
Figure 35.
OUTPUT VOLTAGE vs OUTPUT CURRENT
NO PHASE REVERSAL
20
0°C
15
5
5V/div
VOUT (V)
Output
+85°C
+125°C
10
+125°C
0
-55°C
0°C
+150°C
-5
+18V
-10
-15
37VPP
(±18.5V)
-20
0
10
20
30
40
IOUT (mA)
50
60
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-18V
0.5ms/div
70
Figure 36.
12
OPA211
Output
+85°C
Figure 37.
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SBOS377D – OCTOBER 2006 – REVISED FEBRUARY 2008
APPLICATION INFORMATION
The OPA211 and OPA2211 are unity-gain stable,
precision op amps with very low noise. Applications
with noisy or high impedance power supplies require
decoupling capacitors close to the device pins. In
most cases, 0.1µF capacitors are adequate.
Figure 38 shows a simplified schematic of the
OPA211. This die uses a SiGe bipolar process and
contains 180 transistors.
OPERATING VOLTAGE
OPA211 series op amps operate from ±2.25V to
±18V
supplies
while
maintaining
excellent
performance. The OPA211 series can operate with as
little as +4.5V between the supplies and with up to
+36V between the supplies. However, some
applications do not require equal positive and
negative output voltage swing. With the OPA211
series, power-supply voltages do not need to be
equal. For example, the positive supply could be set
to +25V with the negative supply at –5V or
vice-versa.
The common-mode voltage must be maintained
within the specified range. In addition, key
parameters are assured over the specified
temperature range, TA = –40°C to +125°C.
Parameters that vary significantly with operating
voltage or temperature are shown in the Typical
Characteristics.
V+
Pre-Output Driver
IN-
OUT
IN+
V-
Figure 38. OPA211 Simplified Schematic
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INPUT PROTECTION
RF
-
OPA211
RI
Input
Output
+
Figure 39. Pulsed Operation
NOISE PERFORMANCE
Figure 40 shows total circuit noise for varying source
impedances with the op amp in a unity-gain
configuration (no feedback resistor network, and
therefore no additional noise contributions). Two
different op amps are shown with total circuit noise
calculated. The OPA211 has very low voltage noise,
making it ideal for low source impedances (less than
2kΩ). A similar precision op amp, the OPA227, has
somewhat higher voltage noise but lower current
noise. It provides excellent noise performance at
moderate source impedance (10kΩ to 100kΩ). Above
100kΩ, a FET-input op amp such as the OPA132
(very low current noise) may provide improved
performance. The equation in Figure 40 is shown for
the calculation of the total circuit noise. Note that en =
voltage noise, in = current noise, RS = source
impedance, k = Boltzmann’s constant = 1.38 × 10–23
J/K, and T is temperature in K. For more details on
calculating noise, see the Basic Noise Calculations
section.
14
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10k
Votlage Noise Spectral Density, EO
The input terminals of the OPA211 are protected from
excessive differential voltage with back-to-back
diodes, as shown in Figure 39. In most circuit
applications, the input protection circuitry has no
consequence. However, in low-gain or G = 1 circuits,
fast ramping input signals can forward bias these
diodes because the output of the amplifier cannot
respond rapidly enough to the input ramp. This effect
is illustrated in Figure 29 of the Typical
Characteristics. If the input signal is fast enough to
create this forward bias condition, the input signal
current must be limited to 10mA or less. If the input
signal current is not inherently limited, an input series
resistor can be used to limit the signal input current.
This input series resistor degrades the low noise
performance of the OPA211. See the Noise
Performance section of this data sheet for further
information on noise calculation. Figure 39 shows an
example implementing a current-limiting feedback
resistor.
VOLTAGE NOISE SPECTRAL DENSITY
vs SOURCE RESISTANCE
EO
1k
RS
OPA227
OPA211
100
Resistor Noise
10
2
2
2
EO = en + (in RS) + 4kTRS
1
1k
100
10k
100k
10M
Source Resistance, RS (W)
Figure 40. Noise Performance of the OPA211 in
Unity-Gain Buffer Configuration
BASIC NOISE CALCULATIONS
Design of low-noise op amp circuits requires careful
consideration of a variety of possible noise
contributors: noise from the signal source, noise
generated in the op amp, and noise from the
feedback network resistors. The total noise of the
circuit is the root-sum-square combination of all noise
components.
The resistive portion of the source impedance
produces thermal noise proportional to the square
root of the resistance. This function is plotted in
Figure 40. The source impedance is usually fixed;
consequently, select the op amp and the feedback
resistors to minimize the respective contributions to
the total noise.
Figure 40 depicts total noise for varying source
impedances with the op amp in a unity-gain
configuration (no feedback resistor network, and
therefore no additional noise contributions). The
operational amplifier itself contributes both a voltage
noise component and a current noise component.
The voltage noise is commonly modeled as a
time-varying component of the offset voltage. The
current noise is modeled as the time-varying
component of the input bias current and reacts with
the source resistance to create a voltage component
of noise. Therefore, the lowest noise op amp for a
given application depends on the source impedance.
For low source impedance, current noise is negligible
and voltage noise generally dominates. For high
source impedance, current noise may dominate.
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Figure 41 illustrates both inverting and noninverting
op amp circuit configurations with gain. In circuit
configurations with gain, the feedback network
resistors also contribute noise. The current noise of
the op amp reacts with the feedback resistors to
create additional noise components. The feedback
resistor values can generally be chosen to make
these noise sources negligible. The equations for
total noise are shown for both configurations.
TOTAL HARMONIC DISTORTION
MEASUREMENTS
OPA211 series op amps have excellent distortion
characteristics. THD + Noise is below 0.0001% (G =
+1, VO = 3VRMS) throughout the audio frequency
range, 20Hz to 20kHz, with a 600Ω load.
The distortion produced by OPA211 series op amps
is below the measurement limit of many commercially
available equipment. However, a special test circuit
illustrated in Figure 42 can be used to extend the
measurement capabilities.
feedback factor or noise gain of the circuit. The
closed-loop gain is unchanged, but the feedback
available for error correction is reduced by a factor of
101, thus extending the resolution by 101. Note that
the input signal and load applied to the op amp are
the same as with conventional feedback without R3.
The value of R3 should be kept small to minimize its
effect on the distortion measurements.
Validity of this technique can be verified by
duplicating measurements at high gain and/or high
frequency where the distortion is within the
measurement capability of the test equipment.
Measurements for this data sheet were made with an
Audio Precision System Two distortion/noise
analyzer, which greatly simplifies such repetitive
measurements. The measurement technique can,
however, be performed with manual distortion
measurement instruments.
Op amp distortion can be considered an internal error
source that can be referred to the input. Figure 42
shows a circuit that causes the op amp distortion to
be 101 times greater than normally produced by the
op amp. The addition of R3 to the otherwise standard
noninverting amplifier configuration alters the
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Noise in Noninverting Gain Configuration
Noise at the output:
R2
2
2
EO
R1
= 1+
R2
R1
2
2
en
2
e1
+
EO
2
+ e2 + (inR2) +
R2
Where eS = Ö4kTRS ´ 1 +
2
R1
2
eS
2
+ (inRS)
1+
R2
R1
= thermal noise of RS
RS
R2
e1 = Ö4kTR1 ´
R1
VS
= thermal noise of R1
e2 = Ö4kTR2 = thermal noise of R2
Noise in Inverting Gain Configuration
Noise at the output:
R2
2
2
EO = 1 +
R1
R2
R 1 + RS
2
EO
RS
2
2
2
en + e1 + e2 + (inR2) + eS
R2
Where eS = Ö4kTRS ´
R 1 + RS
2
= thermal noise of RS
VS
R2
e1 = Ö4kTR1 ´
R 1 + RS
= thermal noise of R1
e2 = Ö4kTR2 = thermal noise of R2
For the OPA211 series op amps at 1kHz, en = 1.1nV/ÖHz and in = 1.7pA/ÖHz.
Figure 41. Noise Calculation in Gain Configurations
R1
R2
SIG. DIST.
GAIN GAIN
R3
Signal Gain = 1+
OPA211
VO = 3VRMS
R2
R1
Distortion Gain = 1+
R2
R1 II R3
Generator
Output
R1
R2
R3
1
101
¥
1kW
10W
11
101
100W
1kW
11W
Analyzer
Input
Audio Precision
System Two(1)
with PC Controller
RL
600W
NOTE: (1) Measurement BW = 80kHz.
Figure 42. Distortion Test Circuit
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