Amplifiers: Capture Signals and Drive Precision Systems Advanced Techniques of Higher Performance Signal Processing

Gustavo Castro, Senior Applications Engineer, Wilmington, MA

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2

Today’s Agenda

Operational amplifier design and applications

Op amp noise considerations

Instrumentation amplifiers and applications

ADC driver amplifiers

High common mode voltage applications

Amplifier design tools

3

Analog to Electronic Signal Processing

SENSOR (INPUT)

DIGITAL PROCESSOR AMP CONVERTER

ACTUATOR (OUTPUT)

AMP CONVERTER

4

Analog to Electronic Signal Processing

SENSOR (INPUT)

DIGITAL PROCESSOR AMP CONVERTER

ACTUATOR (OUTPUT)

AMP CONVERTER

5

Amplifiers and Operational Amplifiers

Amplifiers Make a low-level, high-source impedance signal into a high-level, low-source

impedance signal Op amps, power amps, RF amps, instrumentation amps, etc. Most complex amplifiers built up from combinations of op amps

Operational amplifiers Three-terminal device (plus power supplies) Amplify a small signal at the input terminals to a very, very large one at the

output terminal

6

Operational Amplifiers

Operational Op amps can be configured with feedback networks in multiple ways to perform

“operations” on input signals “Operations” include positive or negative gain, filtering, nonlinear transfer

functions, comparison, summation, subtraction, reference buffering, differential amplification, integration, differentiation, etc.

Applications Fundamental building block for analog design Sensor input amplifier Simple and complex filters – antialiasing ADC driver

7

Key Op Amp Performance Features

Bandwidth and Slew Rate The speed of the op amp Bandwidth is the highest operating frequency of the op amp Slew rate is the maximum rate of change of the output Determined by the frequency of the signal and the gain needed

Offset Voltage and Current The errors of the op amp Determines measurement accuracy

Noise Op amp noise limits how small a signal can be amplified with good fidelity

10

Standard Configurations

Non-Inverting

R1

+ -

R2

VIN

VOUT

V1 I1

Vin

11

RVI in

= 21 II =

)(

0

1

2

21

RRVV

RRVV

inout

inout

−=

−=

;

1

11

RVI =1VVin =

)1(1

21

21

11

RRVV

RRVVV

out

out

+=

+=

;

I2

Inverting

+ -

R1

R2 VIN

VOUT

Vin

I1

Virtual Ground Because +VIN = -VIN

11

Op Amp Error Sources

12

IDEAL

OFFSET VOLTAGE (Vos)

INPUT IMPEDANCE (ZIN)

INPUT BIAS CURRENT (Ib)

INPUT OFFSET CURRENT (Ios)

A +

- - +

OUTPUT IMPEDANCE (ZOUT)

IB – The Current into the Inputs [~pA to mA]

Vos – The Difference in Voltage Between the Inputs [µV to mV]

IOS – The Difference Between the + IB and – IB [~IB /10]

ZIN – Input Impedance [MW to GW]

ZOUT – Output Impedance [<1 W]

Avo – Open Loop Gain [V/mV]

BW – Finite Bandwidth [ kHz to GHz)

AN “IDEAL” NON-INVERTING AMPLIFIER

13

+ -

Vin Vout

I1

R1

R2

V1

Vid

1VVV idin =−

outVRR

RV *21

11 +

=

))(1(1

2idinout VV

RRV −+=

DC + AC Errors of a Circuit

PSRRVs

CMRRVen

AVRIVV icm

vo

outsBosid

δ++Σ+++= *

14

)(1idinout VVV −=

β

))*((1PSRR

VsCMRR

VenAVRIVVV cm

vo

outsBosinout

δβ

++Σ+++−=

0_ vGAINLOOP Aβ=

Since en gets multiplied by β1

we get the name “noise gain”

+ -

R2

Rs Vout Vid

Vin

Noise Gain: The noise gain of an op amp can never be less than the signal gain

+

-

IN +

-

+

-

A B C

R1

R2 IN

R1

R2 R2

R1

IN

Signal Gain = 1 + R2/R1

Noise Gain = 1 + R2/R1

Signal Gain = - R2/R1

Noise Gain = 1 + R2/R1

Signal Gain = - R2/R1

Noise Gain = 1 + R2

R1 R3

n Voltage Noise and Offset Voltage of the op amp are reflected to the output by the Noise Gain.

n Noise Gain, not Signal Gain, is relevant in assessing stability.

n Circuit C has unchanged Signal Gain, but higher Noise Gain, thusbetter stability, worse noise, and higher output offset voltage.

INA B C

R1

R2 IN

R1

R2 R2

R1

IN

Signal Gain = 1 + R2/R1

Noise Gain = 1 + R2/R1

Signal Gain = R2/R1

Noise Gain = 1 + R2/R1

Signal Gain =

Noise Gain = 1 + R2

n

n

n

+

-

IN +

-

+

-

A B C

R1

R2 IN

R1

R2 R2

R1

IN

Signal Gain = 1 + R2/R1

Noise Gain = 1 + R2/R1

Signal Gain = - R2/R1

Noise Gain = 1 + R2/R1

Signal Gain = - R2/R1

Noise Gain = 1 + R2

R1 R3

n

n

n

INA B C

R1

R2 IN

R1

R2 R2

R1

IN

Signal Gain = 1 + R2/R1

Noise Gain = 1 + R2/R1

Signal Gain = R2/R1

Noise Gain = 1 + R2/R1

Signal Gain =

Noise Gain = 1 + R2

n

n

n

+

-

IN +

-

+

-

A B C

R1

R2 IN

R1

R2 R2

R1

IN

Signal Gain = 1 + R2/R1

Noise Gain = 1 + R2/R1

Signal Gain = - R2/R1

Noise Gain = 1 + R2/R1

Signal Gain = - R2/R1

Noise Gain = 1 + R2

R1 R3

n Voltage Noise and Offset Voltage of the op amp are reflected to the output by the Noise Gain.

n Noise Gain, not Signal Gain, is relevant in assessing stability.

n Circuit C has unchanged Signal Gain, but higher Noise Gain, thusbetter stability, worse noise, and higher output offset voltage.

INA B C

R1

R2 IN

R1

R2 R2

R1

IN

Signal Gain = 1 + R2/R1

Noise Gain = 1 + R2/R1

Signal Gain = R2/R1

Noise Gain = 1 + R2/R1

Signal Gain =

Noise Gain = 1 + R2

n

n

n

+

-

IN +

-

+

-

A B C

R1

R2 IN

R1

R2 R2

R1

IN

Signal Gain = 1 + R2/R1

Noise Gain = 1 + R2/R1

Signal Gain = - R2/R1

Noise Gain = 1 + R2/R1

Signal Gain = - R2/R1

Noise Gain = 1 + R2

R1 R3

n

n

n

INA B C

R1

R2 IN

R1

R2 R2

R1

IN

Signal Gain = 1 + R2/R1

Noise Gain = 1 + R2/R1

Signal Gain = R2/R1

Noise Gain = 1 + R2/R1

Signal Gain =

Noise Gain = 1 + R2

n

n

n

15

Total Noise Calculation

FCL = CLOSED LOOP BANDWIDTH

R1

VON

Rp

In-

In+

R2

Vn

VR2J

VR1J

VRPJ

+

= BW [(In-2)R22] [NG] + [(In+2)RP

2] [NG] + VN2 [NG] + 4kTR2 [NG-1] + 4kTR1 [NG-1] + 4kTRP [NG]VON

BW = 1.57 FCLFCL = CLOSED LOOP BANDWIDTH

R1

VON

Rp

In-

In+

R2

Vn

VR2J

VR1J

VRPJ

+

R1

VON

Rp

In-

In+

R2

Vn

VR2J

VR1J

VRPJ

+

= BW [(In-2)R22] [NG] + [(In+2)RP

2] [NG] + VN2 [NG] + 4kTR2 [NG-1] + 4kTR1 [NG-1] + 4kTRP [NG]VON = BW [(In-2)R2

2] [NG] + [(In+2)RP2] [NG] + VN

2 [NG] + 4kTR2 [NG-1] + 4kTR1 [NG-1] + 4kTRP [NG]VON

BW = 1.57 FCL

16

Dominant Noise Source Determined by Input Impedance

CONTRIBUTIONFROM

AMPLIFIERVOLTAGE NOISE

AMPLIFIERCURRENT NOISE

FLOWING IN R

JOHNSONNOISE OF R

VALUES OF R

0 3kΩ 300kΩ

3 3 3

0

0

3

7

300

70

RTI NOISE (nV / √ Hz)Dominant Noise Source is Highlighted

R

+

–

EXAMPLE: OP27Voltage Noise = 3nV / √ HzCurrent Noise = 1pA / √ HzT = 25°C

OP27

R2R1

Neglect R1 and R2Noise Contribution

CONTRIBUTIONFROM

AMPLIFIERVOLTAGE NOISE

AMPLIFIERCURRENT NOISE

FLOWING IN R

JOHNSONNOISE OF R

VALUES OF R

0 3kΩ 300kΩ

3 3 3

0

0

3

7

300

70

RTI NOISE (nV / √ Hz)Dominant Noise Source is Highlighted

R

+

–

EXAMPLE: OP27Voltage Noise = 3nV / √ HzCurrent Noise = 1pA / √ HzT = 25°C

OP27

R2R1

Neglect R1 and R2Noise Contribution

17

AD8675

AD8675

1/f Noise Bandwidth

1/f Corner Frequency is a figure of merit for op amp noise performance (the lower the better)

Typical Ranges: 2Hz to 2kHz

Voltage Noise and Current Noise do not necessarily have the same 1/f corner frequency

3dB/Octave

WHITE NOISE

LOG f

CORNER1f

NOISEnV / √Hz

or√Hz

en, in

k

FC

k FC1fen, in =

3dB/Octave

WHITE NOISE

LOG f

CORNER1f

NOISEnV / √Hz

orpA / √Hz

en, in

k

FC

k FC1fen, in =

1/f Corner Frequency is a figure of merit for op amp noise performance (the lower the better)

Typical Ranges: 2Hz to 2kHz

Voltage Noise and Current Noise do not necessarily have the same 1/f corner frequency

3dB/Octave

WHITE NOISE

LOG f

CORNER1f

NOISEnV / √Hz

or√Hz

en, in

k

FC

k FC1fen, in =

3dB/Octave

WHITE NOISE

LOG f

CORNER1f

NOISEnV / √Hz

orpA / √Hz

en, in

k

FC

k FC1fen, in =

18

The Peak-to-Peak Noise in the 0.1 Hz to 10 Hz Bandwidth ADA4528

19

ADA4528

97nV p-p

ADA4528-x World’s Most Accurate Op Amp Low Noise Zero-Drift Amplifier

Key Features Lowest noise zero-drift amp 5.6 nV/√Hz noise floor No 1/f noise

High DC accuracy Low offset voltage: 2.5 µV max Low offset voltage drift: 0.015 µV/ºC max

Rail-to-rail input/output Operating voltage: 2.2 V to 5.5 V

Applications Transducer applications Temperature measurements Electronic scales Medical instrumentation Battery-powered instruments

20

Vos TCVos Isy / Amp CMRR Bandwidth Slew Rate Temp Range Op. Supply 2.5 µV max 0.015 µV/ºC max 1.8 mA max 115 dB min 4 MHz 0.4 V/µs -40°C - 125°C 2.2 V to 5.5 V

ADA4528-1 Single Released ADA4528-2 Dual In Development Package: 8-lead MSOP, 8-lead LFCSP-8 (3 x 3) Price: $1.15 1ku

Package: 8-lead MSOP, 8-lead LFCSP (3 x 3) Sample Availability: Now

No 1/f Noise

5.6nV/√Hz

ADI Advantages World’s Most Accurate Op Amp, Lowest Voltage Noise Zero-

Drift Op Amp

Precision Weigh Scale Design Using the AD7791 24-Bit Sigma-Delta ADC with External ADA4528-1 Zero-Drift Amplifiers (CN0216)

21

24-bit ADC

Noise optimized for DC measurements

ADI Amplifiers Based on Process Innovations Advanced Process Technology Bipolar JFET CMOS iCMOS® High Performance, Low Noise CMOS Process iPolar® High Performance, Low Noise Bipolar Process LD20 Enhanced CMOS

23

Precision Amplifier Enablers

•Overvoltage Protection •Zero Crossover Distortion •Zero-Drift Op Amp •Bias Cancellation Circuitry

Design Techniques

•Low Noise Processes •High Voltage Processes •Feature Rich Processes

Process Technology

•DigiTrim / In Pkg Trim •Laser Trim

Trim Techniques

•Micro Packages •WLCSP/ Bumped Die •Low Stress Polyimide

Package Technology

•Strip Testing •TCVOS on Strip

Test Techniques

24

•Improved Robustness •Higher Performance Amplifiers

•Higher Precision in Small Plastic Packages •High Precision CMOS Products

•Higher Precision in Small Plastic Packages •Greater User Flexibility - Small Form Factors •Greater Functionality in Small Footprint

• Higher Precision, Improves Offset and TCVOS Performance

Resulting Benefits

•Ultralow Noise AMP/REF Designs •Higher Voltage Amplifiers (100 V) •Higher Integration and Added Features

AD8597/9 1 nV/√Hz Ultralow Noise Key Benefits Low Noise, High Precision Low Voltage Noise: 1 nV/√Hz at 1 kHz, 76 nV

from 0.1 Hz to 1 Hz Low Current Noise: 1.5 pA/√Hz Unity Gain Stable with High 50 mA Output Drive ±5V to ±15V Operation

25

Noise THD+N Vos CMRR Bandwidth Slew Rate Temp Range Price @ 1k

1 nV/√Hz –105 dB 120 µV max 120 dB 10 MHz 16 V/µs –40°C to 85°C See website

8-lead SOIC and 8-lead LFCSP (3x3)

Released

SOIC Released

AD8597 Single AD8599 Dual

OUT A 1

- IN A 2

+ IN A 3

- V 4

+ V8

OUT B7

- IN B6

+ IN B5

AD8599

TOP VIEW(Not to Scale)

OUT A 1

- IN A 2

+ IN A 3

- V 4

+ V8

OUT B7

- IN B6

+ IN B5

AD8599

TOP VIEW(Not to Scale)

Applications Professional audio preamps ATE Imaging systems Medical instrumentation Precision detectors

Optimizing AC Performance in an 18-bit, 250 kSPS, PulSAR Measurement Circuit (CN0261)

26

Noise optimized for Mid-range frequencies

Analog to Electronic Signal Processing

SENSOR (INPUT)

DIGITAL PROCESSOR AMP CONVERTER

ACTUATOR (OUTPUT)

AMP CONVERTER

27

20-Bit, Linear, Low Noise, Precision, Bipolar ±10 V DC Voltage Source (CN0191)

28

1 – ppm resolution Needs low noise In all components

Without Buffer

29

DNL vs. Code INL vs. Code

Using a Rail-to-Rail Input Amplifier

30

Crossover point = 1.7 V away from rail.

INL vs. Code DNL vs. Code

SOLUTION: ADA4500 Zero Crossover Amp

31

DNL vs. Code INL vs. Code

What Can Op Amps Do?

Op amps can do anything Amplify Filter Level shift Compare Drive

The circuit design becomes difficult Matching multiple amplifiers Circuit complexity Precision passive components

32

Specialty Amplifiers

Specialty Amplifiers Designed for a specific signal type Extract and amplify only the signal of interest Pick off a small differential signal from a large common-mode voltage Capture and demodulate a low-level AC signal Compress a high-dynamic range signal Provide automatic or controlled gain-changing Send and receive precision signals Provide high-speed low-impedance power output Use the analog domain to its best advantage to prepare a clean signal for the

data converter

33

Integrated “Amplifier” Products

34

2k 2k

ZV

YYXX+

−×−10

)21()21(

Current Sense

Difference Amps

Instrumentation Amplifiers VGAs

Multipliers RMS-DC Converters Thermocouple Amplifiers

5mV/C

[ ]∫=T

mRMS dtTT

VV0

2sin1

Single-Ended vs. Differential Signals

Single-ended signals Signal is measured referred to ground When signals are bipolar (+ and –), negative supplies needed AC signals are typically bipolar or need special “floating,” or capacitive coupling Ground often carries high noise from other signals or power, compromising the

signal

Differential signals Both sides of the signal float “off ground” Signals are separated from ground and other signals High frequency and accuracy usually need differential handling Common mode (average) can be set for single supply Specialized differential/difference amplifiers are needed

35

Instrumentation, Difference, and Differential Amplifiers Instrumentation Amplifiers Amplify differential inputs to a single-ended output Normally both amplifier inputs are high impedance Provide high gain (up to 10,000) and low noise Normally handle low-level signals from sensors

Difference Amplifiers Amplify differential inputs from high common-mode voltage levels Often include input attenuator to allow operation outside supplies High common-mode rejection even at high frequencies

Differential Amplifiers High frequency amplifiers with differential input and output Handle higher-level signals at lower gains Typically used for line driving/receiving and ADC driving

36

Op Amp Subtractor or Difference Amplifier

37

VOUT = (V2 – V1) R2R1

R1 R2

_

+

V1

V2

VOUT

R1' R2'

R2R1 = R2'

R1'R2'R1' CRITICAL FOR HIGH CMR

0.1% TOTAL MISMATCH YIELDS ≈ 66dB CMR FOR R1 = R2

CMR = 20 log10

1 + R2R1

Kr

Where Kr = Total FractionalMismatch of R1/ R2 TOR1'/R2'

EXTREMELY SENSITIVE TO SOURCE IMPEDANCE IMBALANCE

REF

AD8271 : Precision Difference Amplifier with Programmable Gain

38

KEY SPECIFICATIONS

Difference Amplifier: G = ½, 1, 2

Single-ended Amplifier: G = -2 to +3

Low Distortion: 110 dB THD + N Typical (G=1)

15 MHz Bandwidth

80 dB Min CMRR (G=1)

0.08% Max Gain Error

2 ppm/°C Max Gain Drift

2.6 mA Max Supply Current

Wide Power Supply Range: ±2.5 V to ±18 V

Key Benefits Low Distortion Higher Performance Versatile Gain Configurations Easy to Use

Target Applications High Performance Audio/Video In-Amp Building Block ADC Driver

1

7

6

10kΩ

AD8271

10kΩ

10kΩ

10kΩ

20kΩ

20kΩ

10kΩ

–VS

P4

P3

P2

P1

+VS

OUT

N1

N2

N310

9

8

2

3

4

5

AD8270/AD8271 Flexible Gain Configurations

39

=

0736

3-05

3

1

7

10kΩ

AD8271

10kΩ

10kΩ

10kΩ

20kΩ

20kΩ

10kΩ

P4

P3

P2

P1+IN

GND OUT

OUT

N1

N2

N310

9

8

2

3

4

–IN

–IN

+IN

5kΩ

5kΩ

10kΩ

10kΩ

GND

=–IN

+IN

10kΩ

10kΩ

10kΩ

10kΩ

+VS + –VS2

1

7

10kΩ

AD8271

10kΩ

10kΩ

10kΩ

20kΩ

20kΩ

10kΩ

P4

P3

P2

P1+IN

NC NC

OUTOUT

N1

N2

N310

9

8

2

3

4

–IN

–VS

+VS

=–IN

+IN

10kΩ

5kΩ

5kΩ

10kΩ

GND

0736

305

5

1

7

10kΩ

AD8271

10kΩ

10kΩ

10kΩ

20kΩ

20kΩ

10kΩ

P4

P3

P2

P1

OUT

OUT

N1

N2

N310

9

8

2

3

4

–IN

GND

+IN

OUT

G = ½, Ground Reference

G = 1, Mid-Supply Reference

G = 2, Ground Reference

More in Datasheet

AD8271 Application Example: Building High Speed In-Amp CN0122: High Speed Instrumentation Amplifier Using the AD8271

Difference Amplifier and the ADA4627-1 JFET Input Op Amp

Gain-bandwidth product of 20MHz at gain of 200 www.analog.com/CN0122 Uses monolithic difference amplifier for the output amplifier, thereby providing

good dc/ac accuracy with fewer components

40

AD8277 Application Example – Precision Absolute Value Circuit Benefits One single component Cost competitive Simple single-supply operation Wide input and supply range Low supply current Higher performance Fast 0 V crossover response Gain accuracy Offset voltage, temp drifts Low noise gain

41

AD8277A1

–

+

AD8277A2

–

+VIN

VOUT = | VIN |R

R

R

R

R

R

R

R

A1

–

+

A2

–

+VIN

VOUT = | VIN |

R1

R2

R4

R3 R5

D1

D2

R1, R2, R3 = 10kΩR4, R5 = 20kΩ

Conventional precision absolute value circuit requires many fast, high precision (i.e., expensive) components, and has performance issues.

AD8276/AD8277/AD8278/AD8279 Applications – Building Current Sources (Continued)

42

R1

R2

Rload

V+

Io

Vref

Vload

Vout

AD8276

Rg1 40kΩ

-INRg2 40kΩ

Rf1 40kΩ

+

–2

3

+IN

4

-VS1

REF

6

OUT

5

7

+VS

Rf2 40kΩ

SENSE

R1

Rload

+V

Io

Vref

VloadAD8603

+5V

Vout

4 4

31

2

5AD8276

Rg1 40kΩ

-INRg2 40kΩ

Rf1 40kΩ

+

–2

3

+IN

4

-VS1

REF

6

OUT

5

7

+VS

Rf2 40kΩ

SENSE

R1

R2

RloadIo

Vref

Vload

Vout

AD8276

Rg1 40kΩ

-INRg2 40kΩ

Rf1 40kΩ

+

–2

3

+IN

4

-VS1

REF

6

OUT

5

7

+VS

Rf2 40kΩ

SENSE

V+

Io

Vref

5V

AD8276

Rg1 40kΩ

-INRg2 40kΩ

Rf1 40kΩ

+

–2

3

+IN

4

-VS1

REF

6

OUT

5

7

+VS

Rf2 40kΩ

SENSE

R1

Rload

Vload

Vout

Cost sensitive, ≤15 mA output

Higher accuracy, >15 mA output Higher accuracy, ≤15 mA output

Cost sensitive, >15 mA output

The Generic Instrumentation Amplifier (In-Amp)

43

~~

COMMONMODE

VOLTAGEVCM

+

_

RG

IN-AMPGAIN = G

VOUTVREF

COMMON MODE ERROR (RTI) =VCM

CMRR

~

RS/2

RS/2

∆RS

~

~

VSIG2

VSIG2

+

_

+

_

The Three Op Amp In-Amp

VOUTRG

R1'

R1

R2'

R2

R3'

R3

+

_

+

_

+

_

VREF

VOUT = VSIG • 1 +2R1RG

+ VREFR3R2

IF R2 = R3, G = 1 + 2R1RG

CMR ≤ 20log GAIN × 100% MISMATCHCMR ≤ 20log GAIN × 100% MISMATCHCMR ≤ 20log GAIN × 100% MISMATCH

~~

~~

~~

VCM

+

_

+

_

VSIG2

VSIG2

A1

A2

A3

44

Generalized Bridge Amplifier Using an In-Amp

+VB

+

−

IN AMP

REF VOUT

RG

+VS

-VS R+∆R

VB ∆R R

VOUT = GAIN

R+∆R R–∆R

R–∆R

45

1 MΩ

10 nF

10 kΩ

10 kΩ

1 nF

1 nF

100 kΩ

1 µFAD8495

PCBTracesThermocouple

RFIFilter

Thermocouple Amplifier

Filter for50/60 Hz

ReferenceJunction

MeasurementJunction

Common Mode fc = 16 kHzDifferential fc = 1.3 kHz

IncludesReferenceJunction

Compensation

fc = 1.6 Hz

5 mV/°C

GroundConnection

5V

REF

Typical In-Amp Applications

Sensor Interface Pressure Strain Temperature Vibration Current sensing

Measurement of Biopotentials EEG ECG

Market Segments INI, H/C, PCTL, MIL/AERO,

ATE, AUTO…

46

Different Circuit Topologies to build an In amp

3-Op Amp 2-Op Amp

47

Indirect-Current Feedback Current-Mode Correction

+IN

–IN

OUT

REF

+IN

–IN

OUT

REF

OUT

REF

GM1 GM2

(G-1)R

R+IN

–IN

+IN

–IN

OUT

REF

2IE

IE

IE = (V – V )/R1

R1

R2

–IN+IN

Input Common Mode Range in Instrumentation Amplifiers Input common-mode voltage

range is limited in instrumentation amplifiers This is not the same as the input

voltage range of each input Internal amplifiers may get

saturated in the presence of large common-mode voltages

This behavior usually limits single supply operation at low voltage levels

The “diamond” plots are a graphical representation of these operational limits The amplifier will only operate

inside the plot Sometimes is necessary to change

the gain, reference voltage or power supply levels

49

50

Key Features Low Power

115μA

Industry Leading Gain Accuracy and Drift Gain Error: < 50ppm Gain Drift: < 0.5ppm/°C

High CMRR CMRR: 110dB @ all gains (DC to 60Hz)

Wide Input Common Mode Range GND – 0.3V to Vs + 0.3V

Excellent DC Performance Input Offset: 60μV Offset Drift: 0.2μV/°C

Other Key Specifications Single supply: 1.8V to 5.0V Noise RTI: 1.5μVpp (0.1 to10Hz) 70nV/RtHz @ 1kHz

Bandwidth: 10kHz @ G=100 Gain Range: 1-1000 Input RFI Protection Package: 8L MSOP

Applications Medical Instrumentation

Remote Sensing and Hand Held Instrumentation

Precision Bridge and Current Sense Measurements

Consumer Peripherals – Gaming, Distributed Computing

Setting the Gain

–IN

+IN

VREF

R2

R1

G = 1+ R2R1

AD8237 VOUT

REF

FB

AD8237 - Micro Power, Zero-Drift In Amp

51

300mV operation above and below the supply rails with output swing completely independent of input common-mode voltage

Industry Leading Input Voltage Range

Single-Supply Data Acquisition System

+2V

+2V ± 1V

VCM = +2.5V

G = 100

52

AD8237

AD825x Digitally Programmable Gain Instrumentation Amplifier (PGIA) AD8250 Gain settings of 1, 2, 5, 10

AD8251 Fine gain setting of 1, 2, 4, 8

AD8253 Coarse gain setting of 1, 10, 100, 1000

Low noise and low offset with 10MHz bandwidth

54

A1 A0DGND WR

AD8253

+VS –VS REF

OUT

+IN

LOGIC–IN 1

10

8 3

7

4562

9

0698

3-00

1

Additional In-Amp Expert Reading

Available Online: http://www.analog.com/en/content/cu_dh_designers_guide_to_instrumentation

_amps/fca.html

More Resources Under www.analog.com/inamps

55

ADC Driver Amplifiers

Driving ADC inputs ADC switching feeds transient back to input pins ADC driver amp must reject transients to provide accurate signal

High Performance ADCs Recent high performance ADCs have 16 bits and more at 200 MSPS and

higher Such performance requires a differential input signal

Differential Amplifiers Differential or single-ended input converted to differential output Low impedance output stage rejects ADC switching spikes Common-mode level set and gain setting allow optimum match to ADC range

Voltage Reference Buffer ADC transients can reflect back to reference output Op amp buffer with low output impedance at high frequency may be needed

56

Typical Unbuffered Single-Ended Input Transients of CMOS Switched Capacitor ADC

2.57

Note: Data Taken with 50Ω Source Resistances

SAMPLING CLOCK

AD8475: Differential Funnel Amp and ADC Driver Key Features Active precision attenuation (0.4x or 0.8x)

Level-translating VOCM pin sets output common

mode Single-ended to differential conversion Differential rail-to-rail output Input range beyond the rail

Key Specifications 150 MHz bandwidth 10 nV/√Hz output noise 50 V/μS slew rate –112 dB THD + N 1 ppm/°C max gain drift 500 μV max output offset 3 mA supply current

58

Benefits Connect industrial sensors to high

precision differential ADCs Simplify design Enable quick development Reduce PCB size Reduce cost

Applications Process control modules Data acquisition systems Medical monitoring devices ADC driver

Low Voltage ADC Inputs

Large Input Signal

Precision, Low Power, Single-Supply, Fully Integrated Differential ADC Driver for Industrial-Level Signals (CN0180)

60

Interface ±10 V or ±5 V signal on a single-supply amplifier

Integrate 4 Steps in 1 Attenuate Single-ended-to-differential conversion Level-shift Drive ADC

Drive differential 18-bit SAR ADC up to 4 MSPS with few external components

ADC Driver

61

2.4MHzBPF

FROM50ΩSIGNALSOURCE

ADA4932-1

VCM VDD1 VDD2 VIO

VOCM

AD8031

AD7626

0.1µF

0.1µF

+5V

+5V +2.5V +2.5V

R3499Ω

R5499Ω

R253.6Ω

R153.6Ω

C12.2nFR439Ω

0.1µF

0.1µF

0.1µF

R7499Ω

R6499Ω

+2.048V

1

5 6 7 8

–FB

2

9

+IN

3 –IN

4 +FB

16 15 14 13

+7.25V

–2.5V

+VS

–VS

–OUT

+OUT

PAD

R833Ω

R933Ω

11

10

C556pF

C656pF

IN–

IN+

0V TO+4.096V

+4.096VTO 0V

GND

0.1µF 0.1µF 0.1µF

ADA4932 differential output drives differential input of 16-bit 10 MSPS AD7626 ADC

ADR45xx – Ultrahigh Precision, Low Noise, Voltage Reference Product Overview Key Features Ultrahigh accuracy Voltage drift: 2 ppm/°C max., B grade

• 5 ppm/°C max., A grade Low initial output voltage error: ±0.02% max. Long-term drift: 25 ppm/1,000 hours typ.

Excellent noise performance 1/f noise: <0.5 ppm,pp (0.1 Hz to 10 Hz) Wideband noise: <5 μV rms (10 Hz to 10 kHz)

Versatility Input voltage range: 3 V to 15 V Low dropout: 200 mV for +2 mA at +125°C

• 1 V for ADR4520, 0.5 V for ADR4525 Output drive: ±10 mA – no buffer amp needed Quiescent current: 800 µA max

Wide temperature range -40oC to +125oC operation

Applications Medical/industrial/test instrumentation Automotive hybrid battery monitoring

63

Package Temp Price

8-lead SOIC –40°C to +125°C

$2.45 @ 1k (A) $3.45 @ 1k (B)

All Options of the ADR45xx Family ADR4520 2.048 V Samples ADR4525 2.5 V Now ADR4530 3.0 V ADR4533 3.3 V RTS ADR4540 4.096 V Mar 2012 ADR4550 5.0 V

Benefits of Precision Current Sensing

Precision Current Sensing allows for finer/more adjustments in Automotive Control applications Automatic Transmission: Larger number of gear options and smoother shifting Diesel Injection: Better mileage, lower emissions, reduced noise Electric Power Steering: Facilitates transition from Hydraulic to Electro-

Hydraulic Electric Motor: enables higher performance systems Brake-by-wire and Electric Parking Brake Adaptive Suspension Advanced Wiper / Memory Seat / One-Touch Down Window

In General, High-side current sensing allows for: • Lower cost wiring • Improved diagnostics capabilities • Precise current sensing • Improved system efficiencies

64

High-Side vs. Low-Side Current Sensing

65

+ -

High-Side vs. Low-Side Current Sensing

66

67

Typical Applications

DC-DC CONVERTERS BANDWIDTH CMRR over frequency Response time

POWER SUPPLY MONITORING Common Mode Range Gain value Response time

VALVE/SOLENOID CONTROL TEMPERATURE DRIFT Common mode rejection Averaging function

MOTOR CONTROL BIDIRECTIONAL SENSE TEMPERATURE DRIFT Common mode rejection Output linearity to 0V input Response time

SOLAR PANEL MONITORING Inverter / Power Maximizing Common Mode Range Gain value Response time

POWER AMPLIFERS TEMPERATURE DRIFT Common mode rejection

AD8210 – Application Examples

14V

To control circuitry

DC Motor Control DC/DC Converter 42V

Shunt

ECU V Out

G=20

Vs

AD8210

V Ref 2

V Ref 1

- IN + IN

GND

Reference

5V

V Out G=20

Vs

AD8210

V Ref 2

V Ref 1

- IN + IN

GND

V Battery

Motor Control Applications Industrial DC Motor Control Medical Imaging Machine Motor Control Automotive DC Motor and Solenoid Control

DC/DC Converter Applications Power Supply Base Station Battery Charging Automotive Battery Charging

68

High Common-Mode Current Sensing Using the AD629 Difference Amplifier

69

Next generation AD8479 with 600V common mode range coming soon

[Circuit board pic here]

Current Monitor with 500 V Common-Mode Voltage (CN0218) Circuit Features 500 V common mode 0.2% accuracy

Circuit Benefits Minimal loading Fast response

Inputs Power shunt resistor

70

Target Applications Key Parts Used Interface/Connectivity Metering and Energy Monitoring Motor and Power Control Power Supplies

AD8212 AD8605 AD7171 ADuM5402

Isolated SPI

ADIsimOpAmp

73

ADI Diff-Amp Calculator

74

Downloadable Multisim SPICE

75

Tweet it out! @ADI_News #ADIDC13

What We Covered

Op amps are very versatile devices that can be set up for many applications

Op amps cannot amplify an input signal with a higher gain than their own noise – pick low noise op amps

Specialty amplifiers are built-up combinations of op amps with performance tailored to applications

High performance ADCs need high performance driver amplifiers to obtain full accuracy

Differential amplifiers can pick off small signals from very high common-mode voltages

New software and online design tools greatly simplify product selection and system design

76

Design Resources Covered in this Session

Design Tools & Resources:

Ask technical questions and exchange ideas online in our EngineerZone™ Support Community Choose a technology area from the homepage: ez.analog.com

Access the Design Conference community here: www.analog.com/DC13community

77

Name Description URL

ADIsimOpamp On-line tool to select and configure op amps http://designtools.analog.com/dtAPETWeb/dtAPETMain.aspx

Diff Amp Calculator On-line tool to design differential amp circuits http://www.analog.com/en/amplifier-linear-tools/adi-diff-amp-calc/topic.html

Multisim SPICE Downloadable general purpose SPICE simulator http://www.analog.com/en/amplifier-linear-tools/multisim/topic.html

Tweet it out! @ADI_News #ADIDC13

[Circuit board pic here]

Visit the Current Monitor with 500 V Common-Mode Voltage in the Exhibition Room Circuit Features 500 V common mode 0.2% accuracy

Circuit Benefits Minimal loading Fast response

Inputs Power shunt resistor

78

Target Applications Key Parts Used Interface/Connectivity Metering and Energy Monitoring Motor and Power Control

AD8212 AD8605 AD7171 ADuM5402

Isolated SPI

This demo board is available for purchase: www.analog.com/DC13-hardware

Tweet it out! @ADI_News #ADIDC13

Visit the Weigh Scale Demo in the Exhibition Room

79

Measure weights from 0.1 g to 2000 g

This demo board is available for purchase: www.analog.com/DC13-hardware

SOFTWARE OUTPUT DISPLAY

EVAL-CN0216-SDPZ

SDP BOARD