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Authors
W. Stephen Woodward

W. Stephen Woodward

Stephen Woodward

W. Stephen Woodward

Steve Woodward has authored over 50 analog-centric circuit designs. A self-proclaimed "certified, card-carrying analog dinosaur", he is a freelance consultant on instrumentation, sensors, and metrology freelance to organizations such as Agilent Technologies, the Jet Propulsion Laboratory, the Woods Hole Oceanographic Institute, Catalyst Semiconductor, Oak Crest Science Institute, and several international universities. With seven patents to his credit, he has written more than 200 professional articles, and has also served as a member of technical staff at the University of North Carolina. He holds a BS (with honors) in engineering from Caltech, Pasadena, Calif., and an MS in computer science from the University of North Carolina, Chapel Hill.

Areas of interest of the author: Measurement Supply Interfaces Analogue Design Automation Beginners Oscillators Printed Circuit Boards (PCB) Microcontrollers Usage Power ADC, DAC Digital Signal Processing, Filters Amplifiers Solar Audio Light High Voltage Games Wind Energy

Publications on RadioLocman by the author W. Stephen Woodward:

  1. ~0.1% resolution capacitive position sensor
    Jun 8, 2026
  2. Triply simply sequence supply voltages
    Jun 4, 2026
  3. Triple-duty current loop calibrator
    May 21, 2026
  4. ΔVbe thermometer is switchable between °C and °F
    May 14, 2026
  5. ΔVBE thermometer outputs 1 mV/°C without calibration or op amps
    May 7, 2026
  6. ΔVbe + DMM = Celsius, Kelvin, Fahrenheit, and Rankine thermometer
    Apr 30, 2026
  7. BJT is accurate sensor for absolute temperature in Kelvin and Rankine
    Apr 30, 2026
  8. Double-duty current loop transmitter
    Apr 15, 2026
  9. LM555 begets basic bang bang thermostat
    Apr 6, 2026
  10. 1 MHz 555 VFC
    Mar 27, 2026
  11. 5 decade antilogarithmic PWM current source
    Mar 26, 2026
  12. Improve 555 frequency linearity
    Mar 25, 2026
  13. Simple shorts sniffer
    Feb 25, 2026
  14. Silly simple supply sequencing
    Feb 23, 2026
  15. Full circle current loops: 4 mA-20 mA to 0 mA-20 mA
    Feb 13, 2026
  16. Classic constant current cascode
    Feb 5, 2026
  17. 5 octave linear(ish)-in-pitch power VCO
    Jan 30, 2026
  18. Tune 555 frequency over 4 decades
    Jan 29, 2026
  19. Combine two TL431 regulators to make versatile current mirror
    Jan 22, 2026
  20. SCR topology transmogrifies into BJT two-wire precision current source
    Jan 15, 2026
  21. Simple speedy single-slope ADC
    Jan 12, 2026
  22. Active two-way current mirror
    Dec 26, 2025
  23. Ignoring the regulator's reference
    Dec 24, 2025
  24. Two-wire precision current source with wide current range
    Dec 18, 2025
  25. Silly simple precision 0/20 mA to 4/20 mA converter
    Dec 6, 2025
  26. Accuracy loss from PWM sub-Vsense regulator programming
    Nov 27, 2025
  27. Active current mirror
    Nov 27, 2025
  28. Circuit makes square deal
    Nov 25, 2025
  29. A current mirror reduces Early effect
    Nov 7, 2025
  30. Programmable current source with overtemperature shutoff
    Oct 28, 2025
  31. PWM nonlinearity that software can't fix
    Oct 27, 2025
  32. Amps x Volts = Watts
    Oct 19, 2025
  33. PWM buck regulator interface generalized design equations
    Sep 24, 2025
  34. Capacitor matchmaker
    Sep 22, 2025
  35. Positive analog feedback linearizes 4 to 20 mA PRTD transmitter
    Sep 14, 2025
  36. Simple but accurate 4 to 20 mA two-wire transmitter for PRTDs
    Sep 2, 2025
  37. A different twist to the power pushbutton problem: A kilowatt AC DAC
    Aug 26, 2025
  38. Matchmaker
    Aug 19, 2025
  39. Flip ON Flop OFF: high(ish) voltages from the positive supply rail
    Aug 11, 2025
  40. Independent control of thyristor half-wave firing angles via PWM
    Aug 4, 2025
  41. Cross connect complementary current sources to reduce self-heating error
    Jul 30, 2025
  42. PWM + quadrac = pure power play
    Jul 28, 2025
  43. Another weird 555 ADC
    Jul 21, 2025
  44. Inherently DC accurate 16-bit PWM TBH DAC
    Jul 8, 2025
  45. Take back half improves PWM integral linearity and settling time
    Jun 30, 2025
  46. Simple PWM interface can program regulators for VOUT < VSENSE
    Jun 24, 2025
  47. A two-way Wilson current mirror
    Jun 12, 2025
  48. Circuit controls microneedle etching
    Jun 9, 2025
  49. Revisited: Three discretes suffice to interface PWM to switching regulators
    Jun 2, 2025
  50. Precision programmable current sink
    May 22, 2025
  51. A two-way mirror - current mirror that is
    May 22, 2025
  52. Seven-octave linear-in-pitch VCO
    May 21, 2025
  53. Converting square-waves into saw-teeth
    May 12, 2025
  54. LM4041 voltage regulator impersonates precision current source
    Apr 27, 2025
  55. A negative current source with PWM input and LM337 output
    Apr 18, 2025
  56. Photo tachometer sensor accommodates ambient light
    Apr 18, 2025
  57. PWM-programmed LM317 constant current source
    Apr 16, 2025
  58. Flip ON flop OFF without a flip/flop
    Apr 7, 2025
  59. 100-MHz VFC with TBH current pump
    Mar 25, 2025
  60. Can a free running LMC555 VCO discharge its timing cap to zero?
    Mar 24, 2025
  61. Three discretes suffice to interface PWM to switching regulators
    Mar 7, 2025
  62. 1 A, 20V PWM DAC current source with tracking preregulator
    Mar 4, 2025
  63. A precision digital rheostat
    Feb 25, 2025
  64. Tracking preregulator boosts efficiency of PWM power DAC
    Feb 17, 2025
  65. 1-A, 20-V, PWM-controlled current source
    Feb 7, 2025
  66. Flip ON flop OFF
    Feb 6, 2025
  67. Microvolts to kilovolts in milliseconds with one I/O pin
    Jan 24, 2025
  68. Add one resistor to allow DAC control of switching regulator output
    Jan 20, 2025
  69. PWM power DAC incorporates an LM317
    Jan 14, 2025
  70. Capture 16-bit readings of 8 thermistors in less than 1 second for $2
    Jan 14, 2025
  71. PWMpot approximates a Dpot
    Jan 9, 2025
  72. Symmetrical 10 V, 1.5 A PWM-programmed power supply
    Dec 26, 2024
  73. Synthesize precision bipolar Dpot rheostats
    Dec 17, 2024
  74. ∆VBE bread dough incubator
    Dec 10, 2024
  75. 0 V to -10 V, 1.5 A LM337 PWM power DAC
    Dec 2, 2024
  76. RS-232 meets voltage-to-frequency converter
    Nov 19, 2024
  77. Negative time-constant and PWM program a versatile ADC front end
    Nov 18, 2024
  78. Half & Half piezo drive algorithm tames overshoot and ringing
    Nov 12, 2024
  79. 80 MHz VFC with prescaler and preaccumulator
    Oct 28, 2024
  80. Preaccumulator handles VFC outputs that are too fast for a naked CTP to swallow
    Oct 22, 2024
  81. DC-accurate, 32-bit DAC achieves 32-bit resolution
    Oct 21, 2024
  82. Improved PRTD circuit is product of EDN DI teamwork
    Oct 10, 2024
  83. The power of practical positive feedback to perfect PRTDs
    Oct 1, 2024
  84. 20MHz VFC with take-back-half charge pump
    Sep 30, 2024
  85. Take-Back-Half precision diode charge pump
    Sep 26, 2024
  86. Brute force mitigation of PWM VDD and ground "saturation" errors
    Sep 23, 2024
  87. Switch mode hotwire thermostat
    Sep 18, 2024
  88. Digital pot can control gain over a 90 dB span like an electromechanical
    Sep 3, 2024
  89. 8-bit PWM + 8-bit Dpot = 16-bit hybrid DAC
    Aug 29, 2024
  90. Dpot pseudolog + log lookup table = actual logarithmic gain
    Aug 28, 2024
  91. Keep Dpot pseudologarithmic gain control on a leash
    Aug 15, 2024
  92. Synthesize precision Dpot resistances that aren't in the catalog
    Aug 7, 2024
  93. Single supply 200kHz VFC with bipolar differential inputs
    Jul 24, 2024
  94. Voltage inverter design idea transmogrifies into a 1MHz VFC
    Jul 18, 2024
  95. The good, the bad, and the ugly of zero trims
    Jul 18, 2024
  96. Solar day-lamp with active MPPT and no ballast resistors
    Jul 2, 2024
  97. Portable thermal anemometer hot-transistor bias compensation nulls battery discharge droop
    Jun 27, 2024
  98. Getting positive results from NTC thermistors with a simple passive interface
    Jun 25, 2024
  99. I2C active pullup is power thrifty
    Jun 24, 2024
  100. Relay and solenoid driver circuit doubles supply voltage to conserve sustaining power
    May 30, 2024
  101. Improve thermal airflow sensor PSRR with just two resistors
    May 27, 2024
  102. Double and invert 5 V to generate ±10 V using two generic chips and two bootstraps
    May 23, 2024
  103. A groovy apparatus for calibrating miniature high sensitivity anemometers
    May 1, 2024
  104. Efficient digitally regulated bipolar voltage rail booster
    Apr 26, 2024
  105. Driving CMOS totem poles with logic signals, AC coupling, and grounded gates
    Apr 25, 2024
  106. 15-bit voltage-to-time ADC for "Proper Function" anemometer linearization
    Apr 4, 2024
  107. Charge pump halves voltage to double current "efficiency"
    Mar 27, 2024
  108. Efficient voltage doubler is made from generic CMOS inverters
    Mar 14, 2024
  109. Voltage inverter uses gate's output pins as inputs and its ground pin as output
    Mar 13, 2024
  110. ∆Vbe differential thermometer needs no calibration
    Mar 6, 2024
  111. Hotwire thermostat: Using fine copper wire as integrated sensor and heater for temperature control
    Mar 4, 2024
  112. "Sub-zero" op-amp regulates charge pump inverter
    Feb 9, 2024
  113. More gated 555 astable multivibrators hit the ground running
    Jan 23, 2024
  114. Gated 555 astable hits the ground running
    Jan 18, 2024
  115. A simple, accurate, and efficient charge pump voltage inverter for $1 (in singles)
    Jan 10, 2024
  116. Adding one resistor improves anemometer analog linearity to better than ±0.5%
    Dec 29, 2023
  117. New full-wave precision rectifier has versatile current mode outputs
    Dec 22, 2023
  118. Single supply function generator outputs buffered squares, triangles, and sines
    Dec 13, 2023
  119. Force/sense connection eliminates multiplexer on-resistance error
    Dec 8, 2023
  120. Circuit transmits ARINC 429 data
    Dec 4, 2023
  121. Simultaneously control gain on two independent channels with a single element pot
    Nov 23, 2023
  122. Op-amp wipes out DPOT wiper resistance
    Nov 16, 2023
  123. The DAC buddy
    Nov 9, 2023
  124. 3-leg regulator in shunt mode makes variable power supply symmetrical
    Oct 30, 2023
  125. Temperature controller has "take-back-half" convergence algorithm
    Oct 26, 2023
  126. Adjust op-amp gain from -30 dB to +60 dB with one linear pot
    Oct 24, 2023
  127. Low-cost precision adjustable current reference and application
    Oct 19, 2023
  128. A 50 MHz 50:50-square wave output frequency doubler/quadrupler
    Oct 10, 2023
  129. Minimizing passive PWM ripple filter output impedance: How low can you go?
    Oct 5, 2023
  130. Make gain-control multiplexer RON and ROFF errors (mostly) disappear
    Sep 28, 2023
  131. 1 kHz per degree Kelvin temperature sensor
    Sep 8, 2023
  132. Flip-flop plus choke comprise simple and cheap inductive sensor
    Sep 6, 2023
  133. Dual RRIO op amp makes buffered and adjustable triangles and square waves
    Aug 17, 2023
  134. Light powers isolation amplifier
    Jul 27, 2023
  135. Classic 3-leg adjustable regulators have a shunt mode? Who knew?
    Jul 24, 2023
  136. 300 volt, 4 second, self-calibrating Shannon decoder DAC
    Jul 6, 2023
  137. Self-heated ∆Vbe transistor thermostat needs no calibration
    Jul 4, 2023
  138. Shannon decoder DAC meets UART
    Jun 29, 2023
  139. Nonlinearities of Darlington airflow sensor and VFC compensate each other
    Jun 21, 2023
  140. A "free" ADC
    May 22, 2023
  141. Set DC input-stage gain/attenuation over a 96 dB range with PWM
    Apr 28, 2023
  142. Squeeze extra resolution from an 8-bit DAC with Shannon decoder idea
    Apr 26, 2023
  143. DAC (PWM) Controlled Triangle/Sawtooth Generator
    Apr 20, 2023
  144. Adjustable regulator trimmer simple failsafe circuit
    Apr 18, 2023
  145. 555 triangle generator with adjustable frequency, waveshape, and amplitude; and more!
    Feb 9, 2023
  146. Transistor ∆VBE-based oscillator measures absolute temperature
    Jan 10, 2023
  147. The Shannon decoder: A (much) faster alternative to the PWM DAC
    Dec 22, 2022
  148. Cancel PWM DAC ripple and power supply noise
    Nov 24, 2022
  149. CMOS flip-flop used "off label" implements precision capacitance sensor
    Oct 28, 2022
  150. Precision DC motor speed control via pot or DAC
    Oct 12, 2022
  151. Cancel PWM DAC ripple with analog subtraction
    Oct 11, 2022
  152. Linearized portable anemometer with thermostated Darlington pair
    Sep 21, 2022
  153. FemtoAmp offers extreme gain range & isolation
    Sep 13, 2022
  154. Self-heated Darlington transistor pair comprises new air flow sensor
    Aug 23, 2022
  155. New VFC uses flip-flops as high speed, precision analog switches
    Aug 2, 2022
  156. Multiplexed, programmable-gain, track-and-hold amplifier has instrumentation inputs
    Jul 21, 2022
  157. Flying capacitor and negative time constant make digitally programmable-gain instrumentation amplifier
    Jul 21, 2022
  158. Inverted MOSFET helps 555 oscillator ignore power supply and temp variations
    May 19, 2022
  159. Add One Resistor to Give Bipolar LM555 Oscillator a 50:50 Duty Cycle
    Mar 25, 2022
  160. Input buffer and attenuator for sound card oscilloscopes extends low-end frequency response
    Feb 15, 2022
  161. Circuit cancels interconnection resistance to enhance load regulation
    Dec 26, 2021
  162. Series vs shunt linear voltage regulation for small solar-photovoltaic power supplies
    Dec 14, 2021
  163. Series-Connected Transistors Use Differential Heating To Sense Airflow
    Dec 1, 2021
  164. Quickly discharge power-supply capacitors
    May 8, 2021
  165. Circuit for optical reflex sight adds automatic power-off
    Mar 10, 2021
  166. Circuit controls intensity of reflex optical sights
    Mar 3, 2021
  167. DPPs make nonvolatile microvolt DAC
    Dec 21, 2020
  168. Enhanced Circuit Yields Versatile, Efficient Switch-Mode Solenoid/Relay Driver
    Oct 25, 2020
  169. Digital potentiometer simulates log taper to accurately set gain
    Feb 12, 2020
  170. Achieve precision temperature control with TEC Seebeck-voltage sampling
    Dec 3, 2019
  171. Thermoelectric-cooler unipolar drive achieves stable temperatures
    Dec 3, 2019
  172. Diodes derive logarithms and exponentials to optically sense AC/DC current
    Oct 20, 2019
  173. Combine two 8-bit outputs to make one 16-bit DAC
    Jun 19, 2019
  174. Synthesize variable in-circuit Rs, Ls, and Cs
    May 12, 2019
  175. Pseudologarithmic thermistor signal conditioning spans wide temperature range
    Nov 20, 2018
  176. Fast PWM DAC has no ripple
    Oct 9, 2018
  177. Isolated Receiver/Converter Uses Multichannel Opto-Isolator
    Jul 18, 2018
  178. Optically Isolated 4- To 20-mA Current-Loop Transmitter Is Accurate, Inexpensive
    Jul 5, 2018
  179. Inverted dual-slope ADC boosts dynamic range
    Mar 28, 2018
  180. Actively driven ferrite core inductively cancels common-mode voltage
    Feb 22, 2018
  181. Linear wind-power meter compensates for temperature
    Jan 29, 2018
  182. Circuit limits dV/dt and capacitor inrush at regulator turn-on
    Jan 23, 2018
  183. Turn negative regulator «upside-down» to create bipolar supply from single source
    Oct 5, 2017
  184. Square-root function improves thermostat
    Apr 26, 2017
  185. Transistor linearly digitizes airflow
    Jan 31, 2017
  186. Amplifier cancels common-mode voltage
    Jan 11, 2017
  187. Fast-settling synchronous-PWM-DAC filter has almost no ripple
    Nov 9, 2016
  188. Battery-powered amplifier has optical isolation
    Nov 3, 2016
  189. Optoisolators Compute Watts and Volt-Amperes
    Apr 8, 2008
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