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Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
Amplify, Level Shift, and Drive Precision Systems - VE2013
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Amplify, Level Shift, and Drive Precision Systems - VE2013

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Amplifiers are the workhorses of data acquisition and transmission systems. They capture and amplify the low level signals from sensors and transmitters, and can pull these signals from high noise and …

Amplifiers are the workhorses of data acquisition and transmission systems. They capture and amplify the low level signals from sensors and transmitters, and can pull these signals from high noise and high common-mode voltage levels. Amplifiers can also change the signal range and switch from single-ended to differential (or the reverse) to match exactly the input range of an ADC. This session covers the versatility and power of amplifiers in precision systems.

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  • 1. Amplifiers: Capture Signals and Drive Precision Systems Advanced Techniques of Higher Performance Signal Processing Gustavo Castro, Senior Applications Engineer, Wilmington, MA
  • 2. Legal Disclaimer  Notice of proprietary information, Disclaimers and Exclusions Of Warranties The ADI Presentation is the property of ADI. All copyright, trademark, and other intellectual property and proprietary rights in the ADI Presentation and in the software, text, graphics, design elements, audio and all other materials originated or used by ADI herein (the "ADI Information") are reserved to ADI and its licensors. The ADI Information may not be reproduced, published, adapted, modified, displayed, distributed or sold in any manner, in any form or media, without the prior written permission of ADI. THE ADI INFORMATION AND THE ADI PRESENTATION ARE PROVIDED "AS IS". WHILE ADI INTENDS THE ADI INFORMATION AND THE ADI PRESENTATION TO BE ACCURATE, NO WARRANTIES OF ANY KIND ARE MADE WITH RESPECT TO THE ADI PRESENTATION AND THE ADI INFORMATION, INCLUDING WITHOUT LIMITATION ANY WARRANTIES OF ACCURACY OR COMPLETENESS. TYPOGRAPHICAL ERRORS AND OTHER INACCURACIES OR MISTAKES ARE POSSIBLE. ADI DOES NOT WARRANT THAT THE ADI INFORMATION AND THE ADI PRESENTATION WILL MEET YOUR REQUIREMENTS, WILL BE ACCURATE, OR WILL BE UNINTERRUPTED OR ERROR FREE. ADI EXPRESSLY EXCLUDES AND DISCLAIMS ALL EXPRESS AND IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON- INFRINGEMENT OF ANY THIRD PARTY INTELLECTUAL PROPERTY RIGHTS. ADI SHALL NOT BE RESPONSIBLE FOR ANY DAMAGE OR LOSS OF ANY KIND ARISING OUT OF OR RELATED TO YOUR USE OF THE ADI INFORMATION AND THE ADI PRESENTATION, INCLUDING WITHOUT LIMITATION DATA LOSS OR CORRUPTION, COMPUTER VIRUSES, ERRORS, OMISSIONS, INTERRUPTIONS, DEFECTS OR OTHER FAILURES, REGARDLESS OF WHETHER SUCH LIABILITY IS BASED IN TORT, CONTRACT OR OTHERWISE. USE OF ANY THIRD-PARTY SOFTWARE REFERENCED WILL BE GOVERNED BY THE APPLICABLE LICENSE AGREEMENT, IF ANY, WITH SUCH THIRD PARTY. 2
  • 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 3
  • 4. Analog to Electronic Signal Processing SENSOR (INPUT) DIGITAL PROCESSOR AMP CONVERTER ACTUATOR (OUTPUT) AMP CONVERTER 4
  • 5. Analog to Electronic Signal Processing SENSOR (INPUT) DIGITAL PROCESSOR AMP CONVERTER ACTUATOR (OUTPUT) AMP CONVERTER 5
  • 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 6
  • 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 7
  • 8. 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
  • 9. Standard Configurations Non-Inverting R1 + - R2 VIN VOUT V1I1 Vin 1 1 R V I in = 21 II = )( 0 1 2 2 1 R R VV R R V V inout in out −= −= ; 1 1 1 R V I =1VVin = )1( 1 2 1 2 1 1 1 R R VV R R V VV out out += += ; I2 Inverting + - R1 R2 VIN VOUT Vin I1 Virtual Ground Because +VIN = -VIN 11
  • 10. 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)
  • 11. AN “IDEAL” NON-INVERTING AMPLIFIER 13 + - Vin Vout I1 R1 R2 V1 Vid 1VVV idin =− outV RR R V * 21 1 1 + = ))(1( 1 2 idinout VV R R V −+=
  • 12. DC + AC Errors of a Circuit PSRR Vs CMRR V en A V RIVV icm vo out sBosid δ ++Σ+++= * 14 )( 1 idinout VVV −= β ))*(( 1 PSRR Vs CMRR V en A V RIVVV cm vo out sBos in out δ β ++Σ+++−= 0_ vGAINLOOP Aβ= Since en gets multiplied by β 1 we get the name “noise gain” + - R 2 Rs Vout Vid Vin
  • 13. 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, thus better stability, worse noise, and higher output offset voltage. 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 = 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 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 = 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, thus better stability, worse noise, and higher output offset voltage. 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 = 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 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 = Noise Gain = 1 + R2  n n n 15
  • 14. Total Noise Calculation FCL = CLOSED LOOP BANDWIDTH R1 V ON Rp In- In+ R2 V n V R2J V R1J V RPJ + = BW [(In-2)R2 2] [NG] + [(In+2)RP 2] [NG] + VN 2 [NG] + 4kTR2 [NG-1] + 4kTR1 [NG-1] + 4kTRP [NG]VON BW = 1.57 FCL FCL = CLOSED LOOP BANDWIDTH R1 V ON Rp In- In+ R2 V n V R2J V R1J V RPJ + R1 V ON Rp In- In+ R2 V n V R2J V R1J V RPJ + = BW [(In-2)R2 2] [NG] + [(In+2)RP 2] [NG] + VN 2 [NG] + 4kTR2 [NG-1] + 4kTR1 [NG-1] + 4kTRP [NG]VON = BW [(In-2)R2 2] [NG] + [(In+2)RP 2] [NG] + VN 2 [NG] + 4kTR2 [NG-1] + 4kTR1 [NG-1] + 4kTRP [NG]VON BW = 1.57 FCL 16
  • 15. Dominant Noise Source Determined by Input Impedance CONTRIBUTION FROM AMPLIFIER VOLTAGE NOISE AMPLIFIER CURRENT NOISE FLOWING IN R JOHNSON NOISE 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: OP27 Voltage Noise = 3nV / √ Hz Current Noise = 1pA / √ Hz T = 25°C OP27 R2 R1 Neglect R1 and R2 Noise Contribution CONTRIBUTION FROM AMPLIFIER VOLTAGE NOISE AMPLIFIER CURRENT NOISE FLOWING IN R JOHNSON NOISE 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: OP27 Voltage Noise = 3nV / √ Hz Current Noise = 1pA / √ Hz T = 25°C OP27 R2 R1 Neglect R1 and R2 Noise Contribution 17 AD8675 AD8675
  • 16. 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 CORNER 1 f NOISE nV / √Hz or √Hz en, in k FC k FC 1 f en, in = 3dB/Octave WHITE NOISE LOG f CORNER 1 f NOISE nV / √Hz or pA / √Hz en, in k FC k FC 1 f 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 CORNER 1 f NOISE nV / √Hz or √Hz en, in k FC k FC 1 f en, in = 3dB/Octave WHITE NOISE LOG f CORNER 1 f NOISE nV / √Hz or pA / √Hz en, in k FC k FC 1 f en, in = 18
  • 17. The Peak-to-Peak Noise in the 0.1 Hz to 10 Hz Bandwidth ADA4528 19 ADA4528 97nV p-p
  • 18. 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
  • 19. 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
  • 20. 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
  • 21. 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
  • 22. 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
  • 23. Optimizing AC Performance in an 18-bit, 250 kSPS, PulSAR Measurement Circuit (CN0261) 26 Noise optimized for Mid-range frequencies
  • 24. Analog to Electronic Signal Processing SENSOR (INPUT) DIGITAL PROCESSOR AMP CONVERTER ACTUATOR (OUTPUT) AMP CONVERTER 27
  • 25. 20-Bit, Linear, Low Noise, Precision, Bipolar ±10 V DC Voltage Source (CN0191) 28 1 – ppm resolution Needs low noise In all components
  • 26. Without Buffer 29 DNL vs. Code INL vs. Code
  • 27. Using a Rail-to-Rail Input Amplifier 30 Crossover point = 1.7 V away from rail. INL vs. CodeDNL vs. Code
  • 28. SOLUTION: ADA4500 Zero Crossover Amp 31 DNL vs. Code INL vs. Code
  • 29. 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
  • 30. 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
  • 31. Integrated “Amplifier” Products 34 2k2k Z V YYXX + −×− 10 )21()21( Current Sense Difference Amps Instrumentation Amplifiers VGAs MultipliersRMS-DC Converters Thermocouple Amplifiers 5mV/C [ ]∫= T mRMS dtT T VV 0 2 sin 1
  • 32. 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
  • 33. 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
  • 34. Op Amp Subtractor or Difference Amplifier 37 VOUT = (V2 – V1) R2 R1 R1 R2 _ + V1 V2 VOUT R1' R2' R2 R1 = R2' R1' R2' R1' CRITICAL FOR HIGH CMR 0.1% TOTAL MISMATCH YIELDS ≈ 66dB CMR FOR R1 = R2 CMR = 20 log10 1 + R2 R1 Kr Where Kr = Total Fractional Mismatch of R1/ R2 TO R1'/R2' EXTREMELY SENSITIVE TO SOURCE IMPEDANCE IMBALANCE REF
  • 35. 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
  • 36. AD8270/AD8271 Flexible Gain Configurations 39 = 07363-053 1 7 10kΩ AD8271 10kΩ 10kΩ 10kΩ 20kΩ 20kΩ 10kΩ P4 P3 P2 P1 +IN GND OUT OUT N1 N2 N3 10 9 8 2 3 4 –IN –IN +IN 5kΩ 5kΩ 10kΩ 10kΩ GND = –IN +IN 10kΩ 10kΩ 10kΩ 10kΩ +VS + –VS 2 1 7 10kΩ AD8271 10kΩ 10kΩ 10kΩ 20kΩ 20kΩ 10kΩ P4 P3 P2 P1 +IN NC NC OUT OUT N1 N2 N3 10 9 8 2 3 4 –IN –VS +VS = –IN +IN 10kΩ 5kΩ 5kΩ 10kΩ GND 07363055 1 7 10kΩ AD8271 10kΩ 10kΩ 10kΩ 20kΩ 20kΩ 10kΩ P4 P3 P2 P1 OUT OUT N1 N2 N3 10 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
  • 37. 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
  • 38. 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 AD8277 A1 – + AD8277 A2 – + 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 = 10kΩ R4, R5 = 20kΩ Conventional precision absolute value circuit requires many fast, high precision (i.e., expensive) components, and has performance issues.
  • 39. AD8276/AD8277/AD8278/AD8279 Applications – Building Current Sources (Continued) 42 R1 R2 Rload V+ Io Vref Vload Vout AD8276 Rg1 40kΩ -IN Rg2 40kΩ Rf1 40kΩ + –2 3 +IN 4 -VS 1 REF 6 OUT 5 7 +VS Rf2 40kΩ SENSE R1 Rload +V Io Vref Vload AD8603 +5V Vout 4 4 3 1 2 5 AD8276 Rg1 40kΩ -IN Rg2 40kΩ Rf1 40kΩ + –2 3 +IN 4 -VS 1 REF 6 OUT 5 7 +VS Rf2 40kΩ SENSE R1 R2 Rload Io Vref Vload Vout AD8276 Rg1 40kΩ -IN Rg2 40kΩ Rf1 40kΩ + –2 3 +IN 4 -VS 1 REF 6 OUT 5 7 +VS Rf2 40kΩ SENSE V+ Io Vref 5V AD8276 Rg1 40kΩ -IN Rg2 40kΩ Rf1 40kΩ + –2 3 +IN 4 -VS 1 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
  • 40. The Generic Instrumentation Amplifier (In-Amp) 43 ~~ COMMON MODE VOLTAGE VCM + _ RG IN-AMP GAIN = G VOUTVREF COMMON MODE ERROR (RTI) = VCM CMRR ~ RS/2 RS/2 ∆RS ~ ~ VSIG 2 VSIG 2 + _ + _
  • 41. The Three Op Amp In-Amp VOUT RG R1' R1 R2' R2 R3' R3 + _ + _ + _ VREF VOUT = VSIG • 1 + 2R1 RG + VREF R3 R2 IF R2 = R3, G = 1 + 2R1 RG CMR ≤ 20log GAIN × 100 % MISMATCH CMR ≤ 20log GAIN × 100 % MISMATCH CMR ≤ 20log GAIN × 100 % MISMATCH ~~ ~~ ~~ VCM + _ + _ VSIG 2 VSIG 2 A1 A2 A3 44
  • 42. Generalized Bridge Amplifier Using an In-Amp +VB + − IN AMP REF VOUT RG +VS -VSR+∆R VB ∆R R VOUT = GAIN R+∆R R–∆R R–∆R 45
  • 43. 1 MΩ 10 nF 10 kΩ 10 kΩ 1 nF 1 nF 100 kΩ 1 µF AD8495 PCB Traces Thermocouple RFI Filter Thermocouple Amplifier Filter for 50/60 Hz Reference Junction Measurement Junction Common Mode fc = 16 kHz Differential fc = 1.3 kHz Includes Reference Junction Compensation fc = 1.6 Hz 5 mV/°C Ground Connection 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
  • 44. 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
  • 45. 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
  • 46. 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+ R2 R1 AD8237 VOUT REF FB AD8237 - Micro Power, Zero-Drift In Amp
  • 47. 51 300mV operation above and below the supply rails with output swing completely independent of input common- mode voltage Industry Leading Input Voltage Range
  • 48. Single-Supply Data Acquisition System +2V +2V ± 1V VCM = +2.5V G = 100 52 AD8237
  • 49. 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 06983-001
  • 50. 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
  • 51. 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
  • 52. Typical Unbuffered Single-Ended Input Transients of CMOS Switched Capacitor ADC 2.57 Note: Data Taken with 50Ω Source Resistances SAMPLING CLOCK
  • 53. 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
  • 54. 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
  • 55. ADC Driver 61 2.4MHz BPF FROM 50Ω SIGNAL SOURCE ADA4932-1 VCM VDD1 VDD2 VIO VOCM AD8031 AD7626 0.1µF 0.1µF +5V +5V +2.5V +2.5V R3 499Ω R5 499Ω R2 53.6Ω R1 53.6Ω C1 2.2nF R4 39Ω 0.1µF 0.1µF 0.1µF R7 499Ω R6 499Ω +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 R8 33Ω R9 33Ω 11 10 C5 56pF C6 56pF IN– IN+ 0V TO +4.096V +4.096V TO 0V GND 0.1µF 0.1µF 0.1µF ADA4932 differential output drives differential input of 16-bit 10 MSPS AD7626 ADC
  • 56. 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
  • 57. 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
  • 58. High-Side vs. Low-Side Current Sensing 65 + -
  • 59. High-Side vs. Low-Side Current Sensing 66
  • 60. 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
  • 61. AD8210 – Application Examples 14V To control circuitry DC Motor Control DC/DC Converter42V 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
  • 62. High Common-Mode Current Sensing Using the AD629 Difference Amplifier 69 Next generation AD8479 with 600V common mode range coming soon
  • 63. [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
  • 64. ADIsimOpAmp 73
  • 65. ADI Diff-Amp Calculator 74
  • 66. Downloadable Multisim SPICE 75
  • 67. 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
  • 68. 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/dtAPET Main.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
  • 69. 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
  • 70. 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

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