Rarely Asked Questions

RAQ: 137
Issue 137, January 2017

Psychotic ADC?

Question: I was initially testing one of your ADCs successfully, and suddenly I started getting some rather bizarre FFT results. What’s going on?

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RAQ: Issue 136
Issue 136, December 2016

Precision Current Outputs Are Easy to Make

Question: How do I design a circuit with an accurate current output into a nonlinear load resistance?

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RAQ: Issue 135
Issue 135, November 2016

Amplifier RF: Think Before you Choose!

Question: I’m selecting an op amp for my precision signal path. Isn’t faster always better?

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  • RAQ: Issue 134

    Because Mr. Ohm Said So …

    Issue 134, October 2016
  • RAQ: Issue 133

    Common Sense for Current Sensing

    Issue 133, September 2016
  • RAQ:  Issue 132

    Choosing a Precision Op Amp? Trust Goldilocks.

    Issue 132, August 2016
  • RAQ:  Issue 131

    Going Full Tilt

    Issue 131, July 2016
  • RAQ:  Issue 130

    Who Killed the Component?

    Issue 130, June 2016
  • RAQ:  Issue 129

    Who Ate My dBs?

    Issue 129, May 2016
  • RAQ:  Issue 128

    Citius, Altius, Fortius

    Issue 128, April 2016
  • RAQ:  Issue 127

    Kalman or FIR Filter for My IMU?

    Issue 127, March 2016
  • RAQ:  Issue 126

    When Second Sources Aren't

    Issue 126, February 2016
  • RAQ:  Issue 125

    O CMRR, CMRR! Wherefore Art Thou CMRR?

    Issue 125, January 2016
  • RAQ:  Issue 124

    Missing Half the Signal

    Issue 124, December 2015
  • RAQ:  Issue 123

    Unused Pins

    Issue 123, November 2015
  • RAQ:  Issue 122

    The Truth About Voltage Feedback Resistors

    Issue 122, October 2015
  • RAQ:  Issue 121

    Unfiltered Analog

    Issue 121, September 2015
  • RAQ:  Issue 120

    Voltage References Can Bite You, Too

    Issue 120, August 2015
  • RAQ:  Issue 119

    The Ingenious Gentleman and the Mysterious Paddle

    Issue 119, July 2015
  • RAQ:  Issue 118

    Mystery Spur Explained: Don't Blame the DDC!

    Issue 118, June 2015
  • RAQ:  Issue 117

    Murphy Rules!

    Issue 117, May 2015
  • RAQ:  Issue 116

    Muntzing can save cost, components, and even your sanity

    Issue 116, April 2015
  • RAQ:  Issue 115

    Isn’t that gain specification a bit lopsided?

    Issue 115, March 2015
  • RAQ:  Issue 114

    Choosing Voltage References

    Issue 114, February 2015
  • RAQ:  Issue 113

    Don’t Get Caught Speeding

    Issue 113, January 2015
  • RAQ:  Issue 112

    Exposed Paddles and Downbonds Improve Performance and Reduce Pin Count

    Issue 112, December 2014
  • RAQ:  Issue 111

    Choosing Analog ICs

    Issue 111, November 2014
  • RAQ:  Issue 110

    I Grew Up in the 80s and Survived!

    Issue 110, October 2014
  • RAQ:  Issue 109

    ADCs for High Dynamic Range – Successive-Approximation or Sigma-Delta?

    Issue 109, September 2014
  • RAQ:  Issue 108

    LEDs are Photodiodes Too

    Issue 108, August 2014
  • RAQ:  Issue 107

    The Diamond Plot

    Issue 107, July 2014
  • RAQ:  Issue 106

    Overranged Converter Recovers Quickly

    Issue 106, June 2014
  • RAQ:  Issue 105

    Discretion is the better part…

    Issue 105, May 2014
  • RAQ:  Issue 104

    Looking for Trouble in All the Wrong Places

    Issue 104, April 2014
  • RAQ:  Issue 103

    Programmable ADC Input Range Provides System Benefits

    Issue 103, March 2014
  • RAQ:  Issue 102

    Defying Scrooge

    Issue 102, February 2014
  • RAQ:  Issue 101

    Bits Per Second Make My Head Hertz

    Issue 101, January 2014
  • RAQ:  Issue 100

    RAQs: 100 Issues and Counting

    Issue 100, December 2013
  • RAQ:  Issue 99

    Overrange Flag Indicates Data Validity

    Issue 99, November 2013
  • RAQ:  Issue 98

    Design Tools and Support Communities Make Analog Fun, not Fearful

    Issue 98, October 2013
  • RAQ:  Issue 97

    EngineerZone Makes Getting Answers a Breeze

    Issue 97, September 2013
  • RAQ:  Issue 96

    Soft Clipping vs. Hard Clipping

    Issue 96, August 2013
  • RAQ:  Issue 95

    Do-it-Yourself ASICs

    Issue 95, July 2013
  • RAQ:  Issue 94

    Crystal Radio Sets and Op Amps—Both Can Detect RF Signals

    Issue 94, June 2013
  • RAQ: Issue 93

    Input Magic—Differential Signals Allow Input Swing to Exceed Supply Voltage

    Issue 93, May 2013
  • RAQ:  Issue 92

    Multipliers and Modulators

    Issue 92, April 2013
  • RAQ:  Issue 91

    Noise Gain vs. Signal Gain

    Issue 91, March 2013
  • RAQ:  Issue 90

    Resolution vs. ENOB – Still Hazy After All These Years

    Issue 90, February 2013
  • RAQ:  Issue 89

    Electronics is Fun

    Issue 89, January 2013
  • RAQ:  Issue 88

    The Decline of Rounding—or How Significant is Significance?

    Issue 88, December 2012
  • RAQ:  Issue 87

    Apples and Oranges—Correlating Specifications Requires Common Test Conditions

    Issue 87, November 2012
  • RAQ:  Issue 86

    Current Transformers—and Vacuum Cleaners

    Issue 86, October 2012
  • RAQ:  Issue 85

    Great Expectations Come From Basic Understandings

    Issue 85, September 2012
  • RAQ:  Issue 84

    Driving Miss ADC

    Issue 84, August 2012
  • RAQ:  Issue 83

    Dual Op Amps and Double Agents

    Issue 83, July 2012
  • RAQ:  Issue 82

    Transformers: They’re Not All Boat Anchors

    Issue 82, June 2012
  • RAQ:  Issue 81

    Switching Bits

    Issue 81, May 2012
  • RAQ:  Issue 80

    The Electromotive Force and Op Amps

    Issue 80, April 2012
  • RAQ:  Issue 79

    Nobody is Perfect – Not Even an Engineer!

    Issue 79, March 2012
  • RAQ:  Issue 78

    Considerations on High-Speed Converter PCB Design, Part 4: Plane Coupling

    Issue 78, February 2012
  • RAQ:  Issue 77

    Beware of big claims and large numbers.

    Issue 77, January 2012
  • RAQ:  Issue 76

    In and Out – or – Why Have a Capacitor?

    Issue 76, December 2011
  • RAQ:  Issue 75

    Crosstalkin’ Converters

    Issue 75, November 2011
  • RAQ:  Issue 74

    Rotary Potentiometers: There Must Be a Better Option

    Issue 74, October 2011
  • RAQ:  Issue 73

    The Benefits of Ancient Logic

    Issue 73, September 2011
  • RAQ:  Issue 72

    Balancing Phase in High-Speed Converters

    Issue 72, August 2011
  • RAQ:  Issue 71

    Looking for savings in all the wrong places

    Issue 71, July 2011
  • RAQ:  Issue 70

    Do Something with that Unused Pin!

    Issue 70, June 2011
  • RAQ:  Issue 69

    Considerations on High-Speed Converter PCB Design, Part 3: The E-Pad Low Down

    Issue 69, May 2011
  • RAQ:  Issue 68

    A Foolish Question about Op Amps and Capacitors

    Issue 68, April 2011
  • RAQ:  Issue 67

    Measuring the DC Parameters of Op Amps

    Issue 67, March 2011
  • RAQ:  Issue 66

    Considerations on High-Speed Converter PCB Design, Part 2: Power and Ground Planes.

    Issue 66, February 2011
  • RAQ:  Issue 65

    Op Amp Dedicated Feedback Pin Helps Achieve New Levels of Performance.

    Issue 65, January 2011
  • RAQ:  Issue 64

    Oversampling and Undersampling

    Issue 64, December 2010
  • RAQ:  Issue 63

    Considerations on High-Speed Converter PCB Design, Part 1: Power and Ground Planes.

    Issue 63, November 2010
  • RAQ:  Issue 62

    Is amplifier headroom cramping your style?

    Issue 62, October 2010
  • RAQ:  Issue 61

    Make do!

    Issue 61, September 2010
  • RAQ:  Issue 60

    Watch for Those Multiple Clocking Edges!

    Issue 60, August 2010
  • RAQ:  Issue 59

    Is Your Amplifier Disabled, or is it Merely Sleeping?

    Issue 59, July 2010
  • RAQ:  Issue 58

    How to Avoid Burning Cakes

    Issue 58, June 2010
  • RAQ:  Issue 57

    Keeping Your A/D Converter Clocks Jitter Free

    Issue 57, May 2010
  • RAQ:  Issue 56

    Amplifier, attenuator or both?

    Issue 56, April 2010
  • RAQ:  Issue 55

    Taming A/D Converter Power Supplies

    Issue 55, March 2010
  • RAQ:  Issue 54

    Don’t be Mean - be Root Mean Square!

    Issue 54, February 2010
  • RAQ:  Issue 53

    VFB or CFB that is the question!

    Issue 53, January 2010
  • RAQ:  Issue 52

    Bring on the Converter Noise! – Part 2

    Issue 52, December 2009
  • RAQ:  Issue 51

    Bring on the Converter Noise! – Part 1

    Issue 51, November 2009
  • RAQ:  Issue 50

    What’s the big deal about ABSOLUTE MAXIMUM RATINGS?

    Issue 50, October 2009
  • RAQ:  Issue 49

    What’s the (Converter) Frequency Kenneth?

    Issue 49, September 2009
  • RAQ:  Issue 48

    Some Chips Have Moving Parts!

    Issue 48, August 2009
  • RAQ:  Issue 47

    Which carries more weight, a datasheet or SPICE macromodel?

    Issue 47, July 2009
  • RAQ:  Issue 46

    What shall we do with an unused op-amp?

    Issue 46, June 2009
  • RAQ:  Issue 45

    Glass Diodes May See the Light — and Hum

    Issue 45, May 2009
  • RAQ:  Issue 44

    Keeping Common Modes Common

    Issue 44, April 2009
  • RAQ:  Issue 43

    Impedance Measuring Chip Offers Little Resistance to Applications

    Issue 43, March 2009
  • RAQ:  Issue 42

    Are Your Filters Filtering?

    Issue 42, February 2009
  • RAQ:  Issue 41

    What’s in Your Toolbox?

    Issue 41, January 2009
  • RAQ:  Issue 40

    How Big Is It?

    Issue 40, December 2008
  • RAQ:  Issue 39

    What The Heck Are Off-Amps?

    Issue 39, November 2008
  • RAQ:  Issue 38

    Single Supply Amplifiers—They Sound Simple…are they?

    Issue 38, October 2008
  • RAQ:  Issue 37

    Lock Down That Noise — Don’t Let It Escape

    Issue 37, September 2008
  • RAQ:  Issue 36

    The Difference Between Different Differential Amplifiers

    Issue 36, August 2008
  • RAQ:  Issue 35

    Stress Is Bad For You — and For Analog ICs

    Issue 35, July 2008
  • RAQ:  Issue 34

    A Capaciticectomy? Sounds Awfully Painful!

    Issue 34, June 2008
  • RAQ:  Issue 33

    Hysteresis Blocks Magic

    Issue 33, May 2008
  • RAQ:  Issue 32

    Political Correctness and Datasheets

    Issue 32, April 2008
  • RAQ:  Issue 31

    Too Hot or Too Cold May Be Just Right*

    Issue 31, March 2008
  • RAQ:  Issue 30

    Capacitive Sensors: Rugged Enough for the Real World?

    Issue 30, February 2008
  • RAQ:  Issue 29

    Half Full or Half Empty? Thoughts on Capacity.

    Issue 29, January 2008
  • RAQ:  Issue 28

    What's Your Amplifier's Febricity Due to Electricity?

    Issue 28, December 2007
  • RAQ:  Issue 27

    Resistors Have Hidden Depths

    Issue 27, November 2007
  • RAQ:  Issue 26

    Op-Amp Noise can be Deafening Too

    Issue 26, October 2007
  • RAQ:  Issue 25

    Resistor Noise can be Deafening, and Hard to Reduce

    Issue 25, September 2007
  • RAQ:  Issue 24

    Are leaky amps sinking your design?

    Issue 24, August 2007
  • RAQ:  Issue 23

    Should you butcher your circuit or your test gear?

    Issue 23, June 2007
  • RAQ:  Issue 22

    Things (animals and ADCs) are not always what they seem

    Issue 22, May 2007
  • RAQ:  Issue 20

    Igor, pass me some supply sequencers!

    Issue 20, April 2007
  • RAQ:  Issue 21

    Breadboarding With Surface Mount ICs

    Issue 21, April 2007
  • RAQ:  Issue 19

    Observing Maximum Ratings or How to Avoid Forecasts of Doom

    Issue 19, March 2007
  • RAQ:  Issue 18

    Just How Accurate was William Tell, Anyway?

    Issue 18, February 2007
  • RAQ:  Issue 17

    More Chips are Better than One (or the Benefits of Belgian Food)

    Issue 17, December 2006
  • RAQ:  Issue 16

    Replacing Optocouplers with Digital Isolators

    Issue 16, November 2006
  • RAQ:  Issue 15

    How to Age Gracefully and Avoid Sudden Death

    Issue 15, October 2006
  • RAQ:  Issue 14

    Why Good Engineers Use the Best Components

    Issue 14, September 2006
  • RAQ:  Issue 13

    Sigma Delta Converters are Not Really Hard to Understand

    Issue 13, July 2006
  • RAQ:  Issue 12

    How Not to Design Active Filters

    Issue 12, June 2006
  • RAQ:  Issue 11

    Comparators & Op Amps—May They Never Meet

    Issue 11, May 2006
  • RAQ:  Issue 10

    Digital Processing Does Not Always Rule

    Issue 10, April 2006
  • RAQ:  Issue 9

    Grounding Converters

    Issue 9, March 2006
  • RAQ:  Issue 8

    Happy Groundhog Day!

    Issue 8, February 2006
  • RAQ:  Issue 7

    It’s easy to drive an EE to drink—but what drives one to poetry?

    Issue 7, January 2006
  • RAQ:  Issue 6

    Tick-Tock, Tick-Tock

    Issue 6, December 2005
  • RAQ:  Issue 5

    Check the Bias Current

    Issue 5, November 2005
  • RAQ:  Issue 4

    Caveat Emptor!

    Issue 4, October 2005
  • RAQ:  Issue 3

    Isolating the Key Detail

    Issue 3, September 2005
  • RAQ:  Issue 2

    Slow “starting” ADCs

    Issue 2, July 2005
  • RAQ:  Issue 1

    Radio Frequency Interference (or how to get a free lunch at a very good restaurant)

    Issue 1, June 2005
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