High Precision, Low Noise Operational Amplifiers . (Rev. A)

23
1 2 3 4 8 7 6 5 V+ Out B –In B +In B Out A –In A +In A V– A B D PACKAGE (TOP VIEW) OPA2227-EP www.ti.com SBOS594A – MARCH 2012 – REVISED NOVEMBER 2012 HIGH PRECISION, LOW NOISE OPERATIONAL AMPLIFIER Check for Samples: OPA2227-EP 1FEATURES Low Noise: 3 nV/Hz SUPPORTS DEFENSE, AEROSPACE, AND MEDICAL APPLICATIONS Wide Bandwidth: 8 MHz, 2.3 V/μs Controlled Baseline Settling Time: 5 μs One Assembly and Test Site High CMRR: 138 dB (Typical) One Fabrication Site High Open-Loop Gain: 160 dB (Typical) Available in Military (–55°C to 125°C) Low Input Bias Current: 10 nA Maximum at Temperature Range (1) 25°C Extended Product Life Cycle Low Offset Voltage: 100 μV Maximum at 25°C Extended Product-Change Notification Wide Supply Range: ±2.5 V to ±18 V Product Traceability APPLICATIONS Data Acquisition Telecom Equipment Geophysical Analysis Vibration Analysis Spectral Analysis Professional Audio Equipment Active Filters Power Supply Control (1) Additional temperature ranges available - contact factory DESCRIPTION The OPA2227 operational amplifier combines low noise and wide bandwidth with high precision to make it the ideal choice for applications requiring both ac and precision dc performance. The OPA2227 is unity-gain stable and features high slew rate (2.3 V/μs) and wide bandwidth (8 MHz). The OPA2227 operational amplifier is ideal for professional audio equipment. In addition, low quiescent current and low cost make them ideal for portable applications requiring high precision. The OPA2227 operational amplifier is a pin-for-pin replacement for the industry standard OP-27 with substantial improvements across the board. The dual and quad versions are available for space savings and perchannel cost reduction. The OPA2227 is available in an SOIC-8 package. Operation is specified from –55°C to 125°C. 1 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. PRODUCTION DATA information is current as of publication date. Copyright © 2012, Texas Instruments Incorporated Products conform to specifications per the terms of the Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters.

Transcript of High Precision, Low Noise Operational Amplifiers . (Rev. A)

Page 1: High Precision, Low Noise Operational Amplifiers . (Rev. A)

1

2

3

4

8

7

6

5

V+

Out B

–In B

+In B

Out A

–In A

+In A

V–

A

B

D PACKAGE(TOP VIEW)

OPA2227-EP

www.ti.com SBOS594A –MARCH 2012–REVISED NOVEMBER 2012

HIGH PRECISION, LOW NOISE OPERATIONAL AMPLIFIERCheck for Samples: OPA2227-EP

1FEATURES• Low Noise: 3 nV/√Hz SUPPORTS DEFENSE, AEROSPACE,

AND MEDICAL APPLICATIONS• Wide Bandwidth: 8 MHz, 2.3 V/μs• Controlled Baseline• Settling Time: 5 μs• One Assembly and Test Site• High CMRR: 138 dB (Typical)• One Fabrication Site• High Open-Loop Gain: 160 dB (Typical)• Available in Military (–55°C to 125°C)• Low Input Bias Current: 10 nA Maximum at

Temperature Range (1)25°C• Extended Product Life Cycle• Low Offset Voltage: 100 μV Maximum at 25°C• Extended Product-Change Notification• Wide Supply Range: ±2.5 V to ±18 V• Product Traceability

APPLICATIONS• Data Acquisition• Telecom Equipment• Geophysical Analysis• Vibration Analysis• Spectral Analysis• Professional Audio Equipment• Active Filters• Power Supply Control (1) Additional temperature ranges available - contact factory

DESCRIPTIONThe OPA2227 operational amplifier combines low noise and wide bandwidth with high precision to make it theideal choice for applications requiring both ac and precision dc performance.

The OPA2227 is unity-gain stable and features high slew rate (2.3 V/μs) and wide bandwidth (8 MHz).

The OPA2227 operational amplifier is ideal for professional audio equipment. In addition, low quiescent currentand low cost make them ideal for portable applications requiring high precision.

The OPA2227 operational amplifier is a pin-for-pin replacement for the industry standard OP-27 with substantialimprovements across the board. The dual and quad versions are available for space savings and perchannelcost reduction.

The OPA2227 is available in an SOIC-8 package. Operation is specified from –55°C to 125°C.

1

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications ofTexas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

PRODUCTION DATA information is current as of publication date. Copyright © 2012, Texas Instruments IncorporatedProducts conform to specifications per the terms of the TexasInstruments standard warranty. Production processing does notnecessarily include testing of all parameters.

Page 2: High Precision, Low Noise Operational Amplifiers . (Rev. A)

OPA2227-EP

SBOS594A –MARCH 2012–REVISED NOVEMBER 2012 www.ti.com

This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled withappropriate 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 moresusceptible to damage because very small parametric changes could cause the device not to meet its published specifications.

ORDERING INFORMATION (1)

ORDERABLE PARTTA PACKAGE TOP-SIDE MARKING VID NUMBER TRANSPORT MEDIANUMBER

OPA2227MDREP V62/12610-01XE Tape and Reel, large–55°C to SOIC-8 – D 2227EP125°C OPA2227MDEP V62/12610-01XE-T Tube

(1) For the most current package and ordering information, see the Package Option Addendum at the end of this document, or see the TIwebsite at www.ti.com.

ABSOLUTE MAXIMUM RATINGS (1)

over operating free-air temperature range (unless otherwise noted)

VALUE UNIT

Supply voltage ±18 V

Signal input terminals Voltage (V–) – 0.7 to (V+) + 0.7 V

Current 20 mA

Output short-circuit (to ground) (2) Continuous

Operating temperature -55 to 125 °C

Storage temperature -65 to 150 °C

Junction temperature 150 °C

Lead temperature (soldering, 10 s) 300 °C

(1) Stresses beyond those listed under "absolute maximum ratings" may cause permanent damage to the device. These are stress ratingsonly, and functional operation of the device at these or any other conditions beyond those indicated under "recommended operatingconditions" is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.

(2) One channel per package.

THERMAL INFORMATIONOPA2227

THERMAL METRIC (1) D UNITS

8 PINS

θJA Junction-to-ambient thermal resistance (2) 91.9

θJCtop Junction-to-case (top) thermal resistance (3) 39.9

θJB Junction-to-board thermal resistance (4) 40.6°C/W

ψJT Junction-to-top characterization parameter (5) 3.9

ψJB Junction-to-board characterization parameter (6) 39.6

θJCbot Junction-to-case (bottom) thermal resistance (7) N/A

(1) For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953.(2) The junction-to-ambient thermal resistance under natural convection is obtained in a simulation on a JEDEC-standard, high-K board, as

specified in JESD51-7, in an environment described in JESD51-2a.(3) The junction-to-case (top) thermal resistance is obtained by simulating a cold plate test on the package top. No specific JEDEC-

standard test exists, but a close description can be found in the ANSI SEMI standard G30-88.(4) The junction-to-board thermal resistance is obtained by simulating in an environment with a ring cold plate fixture to control the PCB

temperature, as described in JESD51-8.(5) The junction-to-top characterization parameter, ψJT, estimates the junction temperature of a device in a real system and is extracted

from the simulation data for obtaining θJA, using a procedure described in JESD51-2a (sections 6 and 7).(6) The junction-to-board characterization parameter, ψJB, estimates the junction temperature of a device in a real system and is extracted

from the simulation data for obtaining θJA , using a procedure described in JESD51-2a (sections 6 and 7).(7) The junction-to-case (bottom) thermal resistance is obtained by simulating a cold plate test on the exposed (power) pad. No specific

JEDEC standard test exists, but a close description can be found in the ANSI SEMI standard G30-88.Spacer

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OPA2227-EP

www.ti.com SBOS594A –MARCH 2012–REVISED NOVEMBER 2012

ELECTRICAL CHARACTERISTICSAt TA = 25°C, VS = ±5 V to ±15 V, RL = 10 kΩ (unless otherwise noted).

PARAMETER TEST CONDITIONS MIN TYP MAX UNIT

OFFSET VOLTAGE

Input offset voltage (VOS) ±5 ±100 µV

vs Temperature, TA = -55°C to 125°C ±10 ±250 µV

vs Temperature (dVOS/dT), TA = -55°C to 125°C ±0.1 µV/°C

vs Power supply (PSRR) TA = -55°C to 125°C VS = ±2.5 V to ±18 V ±0.5 ±2.1 µV/V

vs Time 0.2 µV/mo

dc 0.2 µV/VChannel separation (dual)

f = 1 kHz, RL = 5 kΩ 110 dB

INPUT BIAS CURRENT

Input bias current (IB) ±2.5 ±10 nA

TA = -55°C to 125°C See Typical Characteristics

Input offset current (IOS) ±2.5 ±10 nA

TA = -55°C to 125°C See Typical Characteristics

NOISE

Input voltage noise, f = 0.1 Hz to 10 Hz 90 nVp-p

15 nVrms

Input voltage noise density (en) f = 10 Hz 3.5 nV/√Hz

f = 100 Hz 3 nV/√Hz

f = 1 kHz 3 nV/√Hz

Current noise density (in), f = 1 kHz 0.4 pA/√Hz

INPUT VOLTAGE RANGE

Common-mode voltage range (VCM) (V-) + 2 (V+) – 2 VTA = -55°C to 125°C

Common-mode rejection (CMRR) VCM = (V–) + 2 V to (V+) – 2 V 120 138 dB

TA = -55°C to 125°C 108 138 dB

INPUT IMPEDANCE

Differential Open-loop voltage gain (AOL) Ω || pF107 || 12

Common-mode VCM = (V–) + 2 V to (V+) – 2 V Ω || pF109 || 3

OPEN-LOOP GAIN

Open-loop voltage gain (AOL) VO = (V–) + 2 V to (V+) – 2 V, RL = 10 kΩ 132 160

TA = -55°C to 125°C 112 160dB

VO = (V–) + 3.5 V to (V+) – 3.5 V, RL = 600 Ω 132 160

TA = -55°C to 125°C 112 160

FREQUENCY RESPONSE

Gain bandwidth product (GBW) 8 MHz

Slew rate (SR) 2.3 V/µs

Settling time: 0.1% G = 1, 10-V Step, CL = 100 pF 5 µs

0.01% G = 1, 10-V Step, CL = 100 pF 5.6 µs

Overload recovery time VIN x G = VS 1.3 µs

Total harmonic distortion + noise (THD+N) f = 1 kHz, G = 1, VO = 3.5 Vrms 0.00005 %

OUTPUT

Voltage output

TA = -55°C to 125°C RL = 10 kΩ (V-) + 2 (V+) – 2 V

TA = -55°C to 125°C RL = 600 Ω (V-) + 3.5 (V+) – 3.5

Short-circuit current (ISC) ±45 mA

Capacitive load drive (CLOAD) See Typical Characteristics

POWER SUPPLY

Specified voltage range (VS) ±5 ±15 V

Operating voltage range ±2.5 ±18 V

Quiescent current (per amplifier) (IQ) IO = 0 A ±3.7 ±3.95

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Page 4: High Precision, Low Noise Operational Amplifiers . (Rev. A)

1000

10000

100000

1000000

125 130 135 140 145 150

Estim

ate

d L

ife

(H

ou

rs)

Continuous TJ (°C)

OPA2227-EP

SBOS594A –MARCH 2012–REVISED NOVEMBER 2012 www.ti.com

ELECTRICAL CHARACTERISTICS (continued)At TA = 25°C, VS = ±5 V to ±15 V, RL = 10 kΩ (unless otherwise noted).

PARAMETER TEST CONDITIONS MIN TYP MAX UNIT

TA = -55°C to 125°C IO = 0 A ±4.30 mA

TEMPERATURE RANGE

Specified temperature range –55 125 °C

Operating temperature range –55 125 °C

Storage temperature range –65 150 °C

xxx

A. See datasheet for absolute maximum and minimum recommended operating conditions.

B. Silicon operating life design goal is 10 years at 105°C junction temperature (does not include package interconnectlife).

Figure 1. OPA2227-EP Wirebond Life Derating Chart

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Page 5: High Precision, Low Noise Operational Amplifiers . (Rev. A)

20 100 1k 10k 20k

0.01

0.001

0.0001

0.00001

TH

D+

No

ise (

%)

Frequency (Hz)

TOTAL HARMONIC DISTORTION + NOISE

vs FREQUENCY

G = 1, RL = 10kΩ

VOUT = 3.5Vrms

0.01 0.10 1 10 100 1k 10k 100k 1M 10M 100M

180

160

140

120

100

80

60

40

20

0

–20

AO

L(d

B)

0

–20

–40

–60

–80

–100

–120

–140

–160

–180

–200

Ph

ase

(°)

Frequency (Hz)

OPEN-LOOP GAIN/PHASE vs FREQUENCY

G

φ

10.1 10 100 1k 10k 100k 1M

140

120

100

80

60

40

-20

–0

PS

RR

, C

MR

R (

dB

)

Frequency (Hz)

POWER SUPPLY AND COMMON-MODE

REJECTION RATIO vs FREQUENCY

+CMRR

+PSRR

–PSRR

0.1 101 100 1k 10k

100k

10k

1k

100

10

1

Vo

ltag

e N

ois

e (

nV

/√H

z)

Cu

rre

nt N

ois

e (

fA/√

Hz)

Frequency (Hz)

INPUT VOLTAGE AND CURRENT NOISE

SPECTRAL DENSITY vs FREQUENCY

Current Noise

Voltage Noise

10 100 1k 10k 100k 1M

140

120

100

80

60

40

Ch

an

ne

l S

ep

ara

tio

n (

dB

)

Frequency (Hz)

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 similiar or improved

rejection.

INPUT NOISE VOLTAGE vs TIME

1s/div

50

nV

/div

OPA2227-EP

www.ti.com SBOS594A –MARCH 2012–REVISED NOVEMBER 2012

TYPICAL CHARACTERISTICSAt TA = 25°C, RL = 10 kΩ, VS = ±15 V (unless otherwise noted).

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Page 6: High Precision, Low Noise Operational Amplifiers . (Rev. A)

10

8

6

4

2

0

–2

–4

–6

–8

–10

Offse

t V

olta

ge C

ha

ng

e (

µV

)

0 100 150 300

Time from Power Supply Turn-On (s)

WARM-UP OFFSET VOLTAGE DRIFT

50 200 250

VOLTAGE NOISE DISTRIBUTION (10Hz)

Perc

en

t of U

nits (

%)

Noise (nV/√Hz)

3.160 3.25 3.34 3.43 3.51 3.60 3.69 3.78

24

16

8

0

INPUT BIAS CURRENT vs TEMPERATURE

–75 –50 –25 0 25 50 75 100 125

160

150

140

130

120

110

100

90

80

70

60

AO

L,

CM

RR

, P

SR

R (

dB

)

Temperature (°C)

AOL, CMRR, PSRR vs TEMPERATURE

CMRR

PSRR

AOL

–75 –50 –25 0 25 50 75 100 125

60

50

40

30

20

10

0

Sh

ort

-Circu

it C

urr

en

t (m

A)

Temperature (°C)

SHORT-CIRCUIT CURRENT vs TEMPERATURE

+ISC

–ISC

−50

−40

−30

−20

−10

0

10

20

30

40

−60 −40 −20 0 20 40 60 80 100 120 140

Temperature (°C)

Input B

ias C

urr

ent (n

A)

−2

−1

0

1

2

3

4

5

6

−60 −40 −20 0 20 40 60 80 100 120 140

Temperature (°C)

Input O

ffset C

urr

ent (n

A)

INPUT OFFSET CURRENT vs TEMPERATURE

OPA2227-EP

SBOS594A –MARCH 2012–REVISED NOVEMBER 2012 www.ti.com

TYPICAL CHARACTERISTICS (continued)At TA = 25°C, RL = 10 kΩ, VS = ±15 V (unless otherwise noted).

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Page 7: High Precision, Low Noise Operational Amplifiers . (Rev. A)

QUIESCENT CURRENT vs SUPPLY VOLTAGE

20

Supply Voltage (±V)

0 2 4 6 8 10 12 14 16 18

3.8

3.6

3.4

3.2

3.0

2.8

Qu

iesce

nt C

urr

en

t (m

A)

SLEW RATE vs TEMPERATURE

125

Temperature (°C)

–75 –50 –25 0 25 50 75 100

3.0

2.5

2.0

1.5

1.0

0.5

0

Sle

w R

ate

V/V

) Negative Slew Rate

RLOAD = 2kΩ

CLOAD = 100pF

Positive Slew Rate

2.0

1.5

1.0

0.5

0

–0.5

–1.0

–1.5

–2.0

∆I B

(nA

)

0 5 10 15 20 25 30 35 40

Supply Voltage (V)

CHANGE IN INPUT BIAS CURRENT

vs POWER SUPPLY VOLTAGE

Curve shows normalized change in bias current

with respect to VS = ±10V. Typical I B may range

from –2nA to +2nA at VS = ±10V.

CHANGE IN INPUT BIAS CURRENT

vs COMMON-MODE VOLTAGE

15

Common-Mode Voltage (V)

–15 –10 –5 0 5 10

1.5

1.0

0.5

0

–0.5

–1.0

–1.5

∆I B

(nA

)

VS = ±15V

VS = ±5V

Curve shows normalized change in bias current

with respect to VCM = 0V. Typical I B may range

from –2nA to +2nA at VCM = 0V.

100

10

1

Se

ttlin

gT

ime (

µs)

±1 ±10 ±100

Gain (V/V)

SETTLING TIME vs CLOSED-LOOP GAIN

0.01%0.1%

VS = ±15V, 10V Step

CL = 1500pF

RL = 2kΩ

QUIESCENT CURRENT vs TEMPERATURE

100 120 140

Temperature (°C)

–60 –40 –20 0 20 40 60 80

5.0

4.5

4.0

3.5

3.0

2.5

Qu

iesce

nt C

urr

en

t (m

A)

±10V

±5V

±2.5V

±18V

±15V±12V

OPA2227-EP

www.ti.com SBOS594A –MARCH 2012–REVISED NOVEMBER 2012

TYPICAL CHARACTERISTICS (continued)At TA = 25°C, RL = 10 kΩ, VS = ±15 V (unless otherwise noted).

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Page 8: High Precision, Low Noise Operational Amplifiers . (Rev. A)

SMALL-SIGNAL OVERSHOOT

vs LOAD CAPACITANCE

1k100101 10k 100k

Load Capacitance (pF)

70

60

50

40

30

20

10

0

Ove

rsh

oo

t (%

)

Gain = –10

Gain = +10

Gain = +1

Gain = –1

MAXIMUM OUTPUT VOLTAGE vs FREQUENCY

10M

Frequency (Hz)

1k 10k 100k 1M

30

25

20

15

10

5

0

Ou

tpu

t V

olta

ge

(V

p-p

)

VS = ±15V

VS = ±5V

LARGE-SIGNAL STEP RESPONSE

G = –1, CL = 1500pF

5µs/div

2V

/div

SMALL-SIGNAL STEP RESPONSE

G = +1, CL = 1000pF

400ns/div

25m

V/d

iv

SMALL-SIGNAL STEP RESPONSE

G = +1, CL = 5pF

400ns/div

25m

V/d

iv

OUTPUT VOLTAGE SWING vs OUTPUT CURRENT15

14

13

12

11

10

–10

–11

–12

–13

–14

–15

V+

(V+) –1V

(V+) –2V

(V+) –3V

(V–) +3V

(V–) +2V

(V–) +1V

V–

0 10 20 30 40 50 60

Output Current (mA)

Ou

tpu

t V

olta

ge

Sw

ing

(V

)

–55°C

–40°C

–55°C

85°C

25°C

85°C

25°C

–40°C

125°C

125°C

OPA2227-EP

SBOS594A –MARCH 2012–REVISED NOVEMBER 2012 www.ti.com

TYPICAL CHARACTERISTICS (continued)At TA = 25°C, RL = 10 kΩ, VS = ±15 V (unless otherwise noted).

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Page 9: High Precision, Low Noise Operational Amplifiers . (Rev. A)

OPA2227 Output

RF

500Ω

Input

+

OPA2227-EP

www.ti.com SBOS594A –MARCH 2012–REVISED NOVEMBER 2012

APPLICATION INFORMATION

Basic Connection

The OPA2227 is a precision operational amplifier with very low noise. It is unity-gain stable with a slew rate of2.3 V/μs and 8-MHz bandwidth. Applications with noisy or high impedance power supplies may requiredecoupling capacitors close to the device pins. In most cases, 0.1-μF capacitors are adequate.

Offset Voltage and Drift

The OPA2227 has very low offset voltage and drift. To achieve highest dc precision, circuit layout andmechanical conditions should be optimized. Connections of dissimilar metals can generate thermal potentials atthe op amp inputs which can degrade the offset voltage and drift. These thermocouple effects can exceed theinherent drift of the amplifier and ultimately degrade its performance. The thermal potentials can be made tocancel by assuring that they are equal at both input terminals. In addition:• Keep thermal mass of the connections made to the two input terminals similar.• Locate heat sources as far as possible from the critical input circuitry.• Shield operational amplifier and input circuitry from air currents such as those created by cooling fans.

Operating Voltage

OPA2227 operational amplifier operates from ±2.5-V to ±18-V supplies with excellent performance. Unlike mostoperational amplifiers which are specified at only one supply voltage, the OPA2227 is specified for real-worldapplications; a single set of specifications applies over the ±5-V to ±15-V supply range. Specifications areassured for applications between ±5-V and ±15-V power supplies. Some applications do not require equalpositive and negative output voltage swing. Power supply voltages do not need to be equal. The OPA2227 canoperate with as little as 5 V between the supplies and with up to 36 V between the supplies. For example, thepositive supply could be set to 25 V with the negative supply at –5 V or vice-versa. In addition, key parametersare assured over the specified temperature range, –55°C to 125°C. Parameters which vary significantly withoperating voltage or temperature are shown in the Typical Performance Curves.

Offset Voltage Adjustment

The OPA2227 is laser-trimmed for very low offset and drift so most applications will not require externaladjustment.

Input Protection

Back-to-back diodes (see Figure 2) are used for input protection on the OPA2227. Exceeding the turn-onthreshold of these diodes, as in a pulse condition, can cause current to flow through the input protection diodesdue to the amplifier’s finite slew rate. Without external current-limiting resistors, the input devices can bedestroyed. Sources of high input current can cause subtle damage to the amplifier. Although the unit may still befunctional, important parameters such as input offset voltage, drift, and noise may shift.

Figure 2. Pulsed Operation

When using the OPA2227 as a unity-gain buffer (follower), the input current should be limited to 20 mA. This canbe accomplished by inserting a feedback resistor or a resistor in series with the source. Sufficient resistor sizecan be calculated:RX = VS/20 mA - RSOURCE (1)

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VOLTAGE NOISE SPECTRAL DENSITY

vs SOURCE RESISTANCE

100k 1M

Source Resistance, RS (Ω)

100 1k 10k

1.00+03

1.00E+02

1.00E+01

1.00E+00

Vo

tla

ge

No

ise

Sp

ectr

al D

en

sity,

E0

Typ

ica

l a

t 1

k (

V/

Hz)

OPA2227

Resistor Noise

Resistor Noise

OPA2227

RS

EO

EO2 = en

2 + (in RS)2 + 4kTRS

Op Amp

R1

R2

RB = R2 || R1 External Cancellation Resistor

Conventional Op Amp Configuration

OPA2227-EP

SBOS594A –MARCH 2012–REVISED NOVEMBER 2012 www.ti.com

where RX is either in series with the source or inserted in the feedback path. For example, for a 10-V pulse(VS = 10 V), total loop resistance must be 500 Ω. If the source impedance is large enough to sufficiently limit thecurrent on its own, no additional resistors are needed. The size of any external resistors must be carefullychosen since they will increase noise. See the Noise Performance section of this data sheet for furtherinformation on noise calculation. Figure 2 shows an example implementing a current limiting feedback resistor.

Input Bias Current Cancellation

The input bias current of the OPA2227 is internally compensated with an equal and opposite cancellation current.The resulting input bias current is the difference between with input bias current and the cancellation current. Theresidual input bias current can be positive or negative.

When the bias current is cancelled in this manner, the input bias current and input offset current areapproximately equal. A resistor added to cancel the effect of the input bias current (as shown in Figure 3) mayactually increase offset and noise and is therefore not recommended.

Figure 3. Input Bias Current Cancellation

Noise Performance

Figure 4 shows total circuit noise for varying source impedances with the operational amplifier in a unity-gainconfiguration (no feedback resistor network, therefore no additional noise contributions). Two different operationalamplifiers are shown with total circuit noise calculated. The OPA2227 has very low voltage noise, making it idealfor low source impedances (less than 20 kΩ). A similar precision operational amplifier, the OPA277, hassomewhat higher voltage noise but lower current noise. It provides excellent noise performance at moderatesource impedance (10 kΩ to 100 kΩ). Above 100 kΩ, a FET-input op amp such as the OPA132 (very low currentnoise) may provide improved performance. The equation 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 x 10–23 J/K and T is temperature in K. For more details on calculating noise, see “Basic Noise Calculations.”

Figure 4. Noise Performance of the OPA2227 in Unity-Gain Buffer Configuration

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Page 11: High Precision, Low Noise Operational Amplifiers . (Rev. A)

OPA2227-EP

www.ti.com SBOS594A –MARCH 2012–REVISED NOVEMBER 2012

Basic Noise Calculations

Design of low noise operational amplifier circuits requires careful consideration of a variety of possible noisecontributors: noise from the signal source, noise generated in the operational amplifier, and noise from thefeedback network resistors. The total noise of the circuit is the root-sum-square combination of all noisecomponents.

The resistive portion of the source impedance produces thermal noise proportional to the square root of theresistance. This function is shown plotted in Figure 4. Since the source impedance is usually fixed, select theoperational amplifier and the feedback resistors to minimize their contribution to the total noise.

Figure 4 shows total noise for varying source impedances with the operational amplifier in a unity-gainconfiguration (no feedback resistor network and therefore no additional noise contributions). The operationalamplifier itself contributes both a voltage noise component and a current noise component. The voltage noise iscommonly 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 componentof noise. Consequently, the lowest noise operational amplifier for a given application depends on the sourceimpedance. For low source impedance, current noise is negligible and voltage noise generally dominates. Forhigh source impedance, current noise may dominate.

Figure 5 shows both inverting and noninverting operational amplifier circuit configurations with gain. In circuitconfigurations with gain, the feedback network resistors also contribute noise. The current noise of theoperational amplifier reacts with the feedback resistors to create additional noise components. The feedbackresistor values can generally be chosen to make these noise sources negligible. The equations for total noise areshown for both configurations.

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Page 12: High Precision, Low Noise Operational Amplifiers . (Rev. A)

R1

R2

EO

R1

R2

EORS

VS

RS

VS

Noise in Noninverting Gain Configuration

Noise in Inverting Gain Configuration

For op amps at 1kHz, en = 3nV/√Hz and in = 0.4pA/√Hz.

OPA2227-EP

SBOS594A –MARCH 2012–REVISED NOVEMBER 2012 www.ti.com

Figure 5. Noise Calculation in Gain Configurations

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Page 13: High Precision, Low Noise Operational Amplifiers . (Rev. A)

100kΩ

VOUT

1

2

3OPA2227

22pF

10Ω

Device

Under

Test

R4

9.09kΩ

R3

1kΩ

R7

97.6kΩ

R6

40.2kΩ

C2

1µF

C1

1µF C3

0.47µF

C4

22nF

R2

2MΩR8

402kΩ

R5

634kΩ

Input from

Device

Under

Test

R1

2MΩ

(OPA2227)

U1

(OPA2227)

U21

2

3

R10

226kΩ

R9

178kΩ

C5

0.47µF

C6

10nF

R11

178kΩ

(OPA2227)

U27

VOUT

6

5

OPA2227-EP

www.ti.com SBOS594A –MARCH 2012–REVISED NOVEMBER 2012

Figure 6 shows the 0.1-Hz to 10-Hz bandpass filter used to test the noise of the OPA2227. The filter circuit wasdesigned using Texas Instruments’ FilterPro software (available at www.ti.com). Figure 7 shows the configurationof the OPA2227 for noise testing.

Figure 6. 0.1-Hz to 10-Hz Bandpass Filter Used to Test Wideband Noise of the OPA2227

Figure 7. Noise Test Circuit

Copyright © 2012, Texas Instruments Incorporated Submit Documentation Feedback 13

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Page 14: High Precision, Low Noise Operational Amplifiers . (Rev. A)

Output

NOTE: Use metal film resistors

and plastic film capacitor. Circuit

must be well shielded to achieve

low noise.

Responsivity 2.5 x 10≈4V/W

Output Noise 30µVrms, 0.1Hz to 10Hz≈

Dexter 1M

Thermopile

Detector

100Ω 100kΩ

OPA2227

2

3

1

0.1µF

VOUT

VIN

OPA2227

68nF

10nF

33nF

330pF

2.2nF

OPA2227

1.43kΩ 1.91kΩ

2.21kΩ

1.43kΩ

1.1kΩ

1.65kΩ1.1kΩ

fN = 13.86kHz

Q = 1.186

fN = 20.33kHz f = 7.2kHz

Q = 4.519

dc Gain = 1

2

1 6

3 7

5

OPA2227-EP

SBOS594A –MARCH 2012–REVISED NOVEMBER 2012 www.ti.com

Figure 8. Three-Pole, 20-kHz Low Pass, 0.5-dB Chebyshev Filter

Figure 9. Long-Wavelength Infrared Detector Amplifier

14 Submit Documentation Feedback Copyright © 2012, Texas Instruments Incorporated

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Page 15: High Precision, Low Noise Operational Amplifiers . (Rev. A)

200Ω

200Ω

1kΩ

1kΩ

1/2OPA2227

1/2OPA2227

–15V

0.1µF

0.1µF

+15V

Audio

In

This application uses two op amps

in parallel for higher output current drive.

To

Headphone

OPA2227-EP

www.ti.com SBOS594A –MARCH 2012–REVISED NOVEMBER 2012

Figure 10. Headphone Amplifier

Copyright © 2012, Texas Instruments Incorporated Submit Documentation Feedback 15

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Page 16: High Precision, Low Noise Operational Amplifiers . (Rev. A)

R5

50kΩR4

2.7kΩ

VIN

VOUT

R6

2.7kΩ

C1

940pF

C2

0.0047µF

C3

680pF

CW

CW

R2

50kΩR1

7.5kΩ

R3

7.5kΩ

R10

100kΩ

R8

50kΩR7

7.5kΩ

R9

7.5kΩ R11

100kΩCW

Bass Tone Control

Midrange Tone Control

Treble Tone Control

13

1

2

3

2

13

2

13

2

OPA2227

OPA2227-EP

SBOS594A –MARCH 2012–REVISED NOVEMBER 2012 www.ti.com

Figure 11. Three-Band ActiveTone Control (Bass, Midrange and Treble)

16 Submit Documentation Feedback Copyright © 2012, Texas Instruments Incorporated

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Page 17: High Precision, Low Noise Operational Amplifiers . (Rev. A)

PACKAGE OPTION ADDENDUM

www.ti.com 24-Jan-2013

Addendum-Page 1

PACKAGING INFORMATION

Orderable Device Status(1)

Package Type PackageDrawing

Pins Package Qty Eco Plan(2)

Lead/Ball Finish MSL Peak Temp(3)

Op Temp (°C) Top-Side Markings(4)

Samples

OPA2227MDREP ACTIVE SOIC D 8 2500 Green (RoHS& no Sb/Br)

CU NIPDAU Level-3-260C-168 HR -55 to 125 2227EP

V62/12610-01XE ACTIVE SOIC D 8 2500 Green (RoHS& no Sb/Br)

CU NIPDAU Level-3-260C-168 HR -55 to 125 2227EP

(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.

(2) Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availabilityinformation and additional product content details.TBD: The Pb-Free/Green conversion plan has not been defined.Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement thatlead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used betweenthe die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above.Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weightin homogeneous material)

(3) MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.

(4) Only one of markings shown within the brackets will appear on the physical device.

Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on informationprovided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken andcontinues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.

In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.

OTHER QUALIFIED VERSIONS OF OPA2227-EP :

• Catalog: OPA2227

Page 18: High Precision, Low Noise Operational Amplifiers . (Rev. A)

PACKAGE OPTION ADDENDUM

www.ti.com 24-Jan-2013

Addendum-Page 2

NOTE: Qualified Version Definitions:

• Catalog - TI's standard catalog product

Page 19: High Precision, Low Noise Operational Amplifiers . (Rev. A)

TAPE AND REEL INFORMATION

*All dimensions are nominal

Device PackageType

PackageDrawing

Pins SPQ ReelDiameter

(mm)

ReelWidth

W1 (mm)

A0(mm)

B0(mm)

K0(mm)

P1(mm)

W(mm)

Pin1Quadrant

OPA2227MDREP SOIC D 8 2500 330.0 12.4 6.4 5.2 2.1 8.0 12.0 Q1

PACKAGE MATERIALS INFORMATION

www.ti.com 25-Feb-2013

Pack Materials-Page 1

Page 20: High Precision, Low Noise Operational Amplifiers . (Rev. A)

*All dimensions are nominal

Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm)

OPA2227MDREP SOIC D 8 2500 367.0 367.0 35.0

PACKAGE MATERIALS INFORMATION

www.ti.com 25-Feb-2013

Pack Materials-Page 2

Page 21: High Precision, Low Noise Operational Amplifiers . (Rev. A)
Page 22: High Precision, Low Noise Operational Amplifiers . (Rev. A)
Page 23: High Precision, Low Noise Operational Amplifiers . (Rev. A)

IMPORTANT NOTICE

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TI warrants performance of its components to the specifications applicable at the time of sale, in accordance with the warranty in TI’s termsand conditions of sale of semiconductor products. Testing and other quality control techniques are used to the extent TI deems necessaryto support this warranty. Except where mandated by applicable law, testing of all parameters of each component is not necessarilyperformed.

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