Things you can do with diodes

Original Article ↗ Hacker News Discussion ↗

Semiconductor behavior and notation

  • Commenters clarify that the p–n junction’s depletion region having “positive on n, negative on p” is unintuitive but independent of the historical sign choice for electron charge: the region is charged opposite to the majority carriers that are missing.

Expanded analog & RF applications

  • Many additional uses beyond the article:
    • Frequency mixers and ring modulators for heterodyning and audio effects.
    • Varactor diodes as voltage-controlled capacitors in RF filters and tuners.
    • PIN diodes as RF switches above ~1 GHz.
    • Step-recovery diodes for generating extremely sharp pulses and driving high-speed switches.
    • Voltage doublers/multipliers for high-voltage generation.
    • Baker clamps and flyback diodes for faster transistor switching and inductive load protection.
    • Rectennas (RF power harvesting).

Audio, music, and synthesis

  • Diode ring/bridge gain cells in classic compressors; diode ladders and Sallen–Key variants as voltage-controlled filters in vintage synths.
  • Diode-based wave shaping: triangle-to-sine conversion in oscillators, ring modulation, diode clippers and “octave up” circuits, square-law detectors.
  • Detailed discussion of guitar/distortion pedals using antiparallel diodes (including LEDs, germanium, etc.) and the difficulty of accurately modeling their nonlinear behavior.

Power, sensing, and measurement

  • Uses as temperature sensors, quantum/thermal noise and random-number sources, radiation detectors (including in radiotherapy and accelerators), and high-speed samplers.
  • Strings of diodes as simple voltage droppers or crude regulators when only a fixed ~0.7 V step is needed.
  • Diodes in asymmetric RC networks for slow power-up/fast power-down timing (e.g., reset and mute circuits).

Digital logic, ROM, and ADCs

  • Diode logic’s main drawback (no gain) can be mitigated by transistor followers; this leads into RTL, TTL, CMOS logic families.
  • Historical note: diode matrices plus a smaller number of vacuum tubes enabled cheaper, more reliable early computers and boot ROMs.
  • Examples of diode-based ROM (graphics bitmaps) and a simple diode-based ADC (series diodes tapped as comparators).

Solar heating with diodes

  • A claim that diode strings heat more than resistors from the same PV panel sparks debate.
  • Consensus explanation: diodes act as a crude maximum-power-point tracker by better matching panel impedance, not by creating “extra” energy.

Curriculum, accuracy, and criticism

  • Several push back on the article’s claim that diodes are “neglected,” citing mainstream textbooks that treat them extensively.
  • Others highlight technical inaccuracies, especially the linear-looking I–V graph and description of forward conduction, arguing it misrepresents the exponential diode equation.
  • Some see the article as a useful ham-radio-style crash course; others find the pedagogy and rigor lacking.

Low-voltage design and “ideal” diodes

  • At low supply voltages, the ~0.6 V drop is problematic; suggestions include Schottky diodes, MOSFET-based “ideal diode” ICs, and op-amp-based precision rectifiers.