Amplifiers: Capture Signals and Drive Precision Systems (Design Conference 2013)

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

2

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3

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

4

Analog to Electronic Signal Processing

SENSOR(INPUT)

DIGITAL PROCESSOR

AMP CONVERTER

ACTUATOR(OUTPUT)

AMP CONVERTER

5


SENSOR(INPUT)

DIGITALPROCESSOR

AMP CONVERTER

ACTUATOR(OUTPUT)

AMP CONVERTER

6

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

7

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

8

Original Vacuum-Tube Op Amp from Philbrick Research in 1953: It Used ±300 V Supplies

9

AD823 JFET Input Op Amp Simplified Schematic

INPUTS

+VS

-VS

Q57A=19

Q44A=1

Q43

Q58

Q62

R44

S1NS1P

VB

Q49Q61Q72J6J1

Q48

Q35Q53

I1 Q56

Q59A=1

Q17A=19

OUTPUTQ60

R28

(-)

(+)

VBE + 0.3V

BIAS CURRENT = 25pA MAX @ +25°CINPUT OFFSET VOLTAGE = 0.8mV MAX @ +25°CINPUT VOLTAGE NOISE = 15nV/HzINPUT CURRENT NOISE = 1fA/Hz

10

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

11

Standard Configurations

Non-Inverting R1

+ -

R2

VIN

VOUT

V1I1

Vin

11R

VI

in 21 II

)(

0

1

2

21

R

RVV

RR

VV

inout

inout

;

1

11R

VI 1VVin

)1(1

21

21

11

R

RVV

RR

VVV

out

out

;

I2

Inverting

+ -

R1

R2

VIN

VOUT

Vin

I1

Virtual Ground Because +VIN = -VIN

12

Op Amp Error Sources

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)

13

AN “IDEAL” NON-INVERTING AMPLIFIER

+ -

VinVout

I1

R1

R2

V1

Vid

1VVV idin

outVRR

RV *

21

11

))(1(1

2

idinout VVR

RV

14

DC + AC Errors of a Circuit

PSRR

Vs

CMRR

Ven

A

VRIVV

icm

vo

outsBosid

*

)(1

idinout VVV

))*((1

PSRR

Vs

CMRR

Ven

A

VRIVVV

cm

vo

outsBosinout

0_ vGAINLOOP A

Since en gets multiplied by 1

we get the name “noise gain”

+ -

R

2

Rs VoutVid

Vin

15

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

R2R2

R1

IN

Signal Gain = 1 + R2/R1

Noise Gain = 1 + R2/R1

Signal Gain = - R2/R1



Noise Gain = 1 + R2

R1 R3

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

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

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

IN

A B C

R1

R2 IN

R1

R2R2

R1

IN



Signal Gain = R2/R1


Signal Gain =

Noise Gain = 1 + R2

+

-

IN +

-

+

-

A B C

R1

R2 IN

R1

R2R2

R1

IN






Noise Gain = 1 + R2

R1 R3

IN

A B C

R1

R2 IN

R1

R2R2

R1

IN



Signal Gain = R2/R1


Signal Gain =

Noise Gain = 1 + R2

+

-

IN +

-

+

-

A B C

R1

R2 IN

R1

R2R2

R1

IN






Noise Gain = 1 + R2

R1 R3

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

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

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

IN

A B C

R1

R2 IN

R1

R2R2

R1

IN



Signal Gain = R2/R1


Signal Gain =

Noise Gain = 1 + R2

+

-

IN +

-

+

-

A B C

R1

R2 IN

R1

R2R2

R1

IN






Noise Gain = 1 + R2

R1 R3

IN

A B C

R1

R2 IN

R1

R2R2

R1

IN



Signal Gain = R2/R1


Signal Gain =

Noise Gain = 1 + R2

16

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 FCL

FCL = 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

17

Dominant Noise Source Determined by Input Impedance

CONTRIBUTIONFROM

AMPLIFIERVOLTAGE NOISE

AMPLIFIERCURRENT NOISE

FLOWING IN R

JOHNSONNOISE OF R

VALUES OF R

0 3k 300k

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 3k 300k

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

AD8675

AD8675

18

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

orHz

en, in

k

FC

k FC1f

en, in =3dB/Octave

WHITE NOISE

LOG f

CORNER1f

NOISEnV / Hz

orpA / Hz

en, in

k

FC

k FC1f

en, 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

orHz

en, in

k

FC

k FC1f

en, in =3dB/Octave

WHITE NOISE

LOG f

CORNER1f

NOISEnV / Hz

orpA / Hz

en, in

k

FC

k FC1f

en, in =

19

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

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 V max 0.015 V/ºC max 1.8 mA max 115 dB min 4 MHz 0.4 V/s -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

aNo 1/f Noise

5.6nV/Hz

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

Drift Op Amp

21

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

24-bit ADC

Noise optimized forDC measurements

1-22

1) More capacitance, more noise peaking2) Total noise at the output = value of the

noise spectral density integrated over the entire bandwidth

3) Noise is dominated by the noise peak.4) Assuming system –3 dB bandwidth of

16 MHz (25 MHz noise bandwidth)

CL = 8 pF CL = 220 pF CL = 470 pF

95 µV rms 110 µV rms 115 µV rms

http://electronicdesign.com/content/content/74494/74494_F2.jpg

23

ADI AmplifiersBased 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


24

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

•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

AD8597/91 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 V max 120 dB 10 MHz 16 V/s –40°C to 85°C See website

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

Released

SOIC Released

AD8597 Single AD8599 Dual

aOUT 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


26

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

Noise optimized for Mid-range frequencies

27


SENSOR(INPUT)

DIGITALPROCESSOR

AMP CONVERTER

ACTUATOR(OUTPUT)

AMP CONVERTER

28

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

1 – ppm resolutionNeeds low noiseIn all components

Without Buffer

29

DNL vs. Code INL vs. Code

30

Using a Rail-to-Rail Input Amplifier

Crossover point = 1.7 V away from rail.

INL vs. CodeDNL vs. Code

SOLUTION: ADA4500 Zero Crossover Amp

31

DNL vs. Code INL vs. Code

32

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

33

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

Integrated “Amplifier” Products

34

2k2k

ZV

YYXX

10

)21()21(

Current Sense

DifferenceAmps

InstrumentationAmplifiers

VGAs

MultipliersRMS-DC Converters Thermocouple Amplifiers

5mV/C

T

mRMS dtTT

VV0

2sin1

35

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

36

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

37

Op Amp Subtractor or Difference Amplifier

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

a

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

N3

07

363

-032

10

9

8

2

3

4

39

AD8270/AD8271 Flexible Gain Configurations

=

07

363

-053

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

=

–IN

+IN

10kΩ

10kΩ

10kΩ

10kΩ

+VS + –VS

2

07

363

-057

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

+V

=

–IN

+IN

10kΩ

5kΩ

5kΩ

10kΩ

GND

07

36

3-0

55

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

40

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

http://www.analog.com/CN0122

41

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

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.

42

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

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

Vload

AD8603

+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

43

The Generic Instrumentation Amplifier (In-Amp)

~~

COMMONMODE

VOLTAGEVCM

+

_

RG

IN-AMPGAIN = G

VOUTVREF

COMMON MODE ERROR (RTI) =VCM

CMRR

~

RS/2

RS/2

RS

~

~

VSIG2

VSIG2

+

_

+

_

44

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 20logGAIN × 100

% MISMATCHCMR 20log

GAIN × 100% MISMATCH

CMR 20logGAIN × 100

% MISMATCH

~~

~~

~~

VCM

+

_

+

_

VSIG2

VSIG2

A1

A2

A3

45

Generalized Bridge Amplifier Using an In-Amp

+VB

+

-

IN AMP

REF VOUT

RG

+VS

-VSR+DR

VB

DR

RVOUT = GAIN

R+DRR–DR

R–DR

46

1 MΩ

10 nF

10 kΩ

10 kΩ

1 nF

1 nF

100 kΩ

1 µF

AD8495

PCBTraces

Thermocouple

RFIFilter

Thermocouple Amplifier

Filter for50/60 Hz

ReferenceJunction

MeasurementJunction

Common Mode fc = 16 kHz

Differential 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…

47

Different Circuit Topologies to build an In amp

3-Op Amp 2-Op Amp

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

48

CMRR vs. Frequency (Different Topologies)

BEST GOOD

GOOD BETTER

AD8421

AD8420

AD627

AD8553

49

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

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

52

Single-Supply Data Acquisition System

+2V

+2V 1V

VCM = +2.5V

G = 100

AD8237

54

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

A1 A0DGND WR

AD8253

+VS –VS REF

OUT

+IN

LOGIC–IN 1

10

8 3

7

4562

9

55

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

http://www.analog.com/en/content/cu_dh_designers_guide_to_instrumentation_amps/fca.html

http://www.analog.com/en/content/cu_dh_designers_guide_to_instrumentation_amps/fca.html

http://www.analog.com/inamps

56

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

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

2.57

Note: Data Taken with 50 Source Resistances

SAMPLING CLOCK

58

ADC Driver

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 0.1µ

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

59

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

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 InputSignal

60

AD8475: Funnel Amplifier + ADC Driver

AD8475 AD7982

REF

+5V

10kΩ

10kΩ

+IN 0.4x

-IN 0.4xVOCM

+5V

+IN

-IN

20Ω

20Ω270pF

270pF

1.35nF

0.5V – 4.5VVOUT(DIFF) ±4V

0.1µF

4V 2.5V

0.5V – 4.5VVOUT(DIFF) ±4V

4V 2.5V

SNR=97dBTHD=-113dB

ADR435

0V±10V

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

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

61

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

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ADC Driver for High Speed ADCs 100 MSPS 12-Bit 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

65

High-Side vs. Low-Side Current Sensing

+

-

66

High-Side vs. Low-Side Current Sensing

67

Typical Applications

DC-DC CONVERTERSBANDWIDTHCMRR over frequencyResponse time

POWER SUPPLY MONITORINGCommon Mode RangeGain valueResponse time

AD8210

VALVE/SOLENOID CONTROLTEMPERATURE DRIFTCommon mode rejectionAveraging function

MOTOR CONTROLBIDIRECTIONAL SENSETEMPERATURE DRIFTCommon mode rejectionOutput linearity to 0V inputResponse time

SOLAR PANEL MONITORINGInverter / Power MaximizingCommon Mode RangeGain valueResponse time

POWER AMPLIFERSTEMPERATURE DRIFTCommon mode rejection

AD8210 – Application Examples

14V

To control circuitry

DC Motor Control DC/DC Converter42V

Shunt

ECU

V OutG=20

Vs

AD8210

V Ref 2

V Ref 1

- IN+ IN

GND

Reference

5V

V OutG=20

Vs

AD8210

V Ref 2

V Ref 1

- IN+ IN

GND

V Battery

Motor Control ApplicationsIndustrial DC Motor ControlMedical Imaging Machine Motor Control Automotive DC Motor and Solenoid Control

DC/DC Converter ApplicationsPower SupplyBase StationBattery ChargingAutomotive Battery Charging

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69

High Common-Mode Current Sensing Using the AD629 Difference Amplifier

VCM = 270V for VS = 15V

Next generation AD8479 with 600V common mode range coming soon

70

[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

Target Applications Key Parts Used Interface/Connectivity

Metering and Energy MonitoringMotor and Power ControlPower Supplies

AD8212AD8605AD7171ADuM5402

IsolatedSPI

Amplifiers Improve What We See…

The clarity and contrast in this ultrasound comes from the very low noise floor of the VGA, the constancy of the noise over the entire gain range, and the very tight delay variance.

AD8332

71

…. And How We Live!

Did you see an accident today?

ADF4158Xmit Channel

Sig. Generator

PA

AD8283Rx Channel Signal Pxing

DSP

ANTENNA

ADAS systems require multi-channel radar receivers, with finely controlled gain and low channel crosstalk, at very low noise and power factors.

By offering these, AD8283 AFE makes it possible to eliminate most accidentsat speeds less than 25 mph.

72

73

ADIsimOpAmp

74

ADI Diff-Amp Calculator

75

Downloadable Multisim SPICE

76 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

77

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

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

http://ez.analog.com/welcome

http://www.analog.com/DC13community


[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

Target Applications Key Parts Used Interface/Connectivity

Metering and Energy MonitoringMotor and Power Control

AD8212AD8605AD7171ADuM5402

IsolatedSPI

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

http://www.analog.com/DC13-hardware


Visit the Weigh Scale Demo in the Exhibition Room

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

http://www.analog.com/DC13hardware

Amplifiers: Capture Signals and Drive Precision Systems (Design Conference 2013)

Technology

Transcript of Amplifiers: Capture Signals and Drive Precision Systems (Design Conference 2013)