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Electronic Engineers Master Catalog
19 days ago
- Electronic Engineers Master Catalog for 1984-1985, Volume 1B
- Published in 1985, part of the Digital Library of Amateur Radio & Communications collection
- File size is 3.6G, contains 1282 pages with some scanning and formatting issues
A Brief History of the Crazy Old 7-Segment Display
14 days ago
- The concept of seven-segment displays dates back to the early 1900s, with patents filed around 1908-1910, predating the 1970s by decades.
- Early implementations used incandescent lamps or neon tubes in the 1930s-1940s, before LEDs became practical in the late 1960s.
- Seven segments became standard for balancing readability with minimal hardware, though variations like 14- or 16-segment 'Union Jack' displays emerged for better alphanumeric support.
- The design principle involves starting with the most complex digit (like an 8) and selectively removing segments to form others, a concept seen even in manual price tags.
- Seven-segment displays persist due to their simplicity and adaptability across technologies, from LEDs and LCDs to older mechanical systems.
Tech note: making your own V-I plots at home
7 days ago
- The author prefers real data for circuit illustrations in their book, avoiding fake or retraced diagrams.
- Measuring V-I plots for semiconductors is challenging due to tiny currents, sudden spikes causing device failure, and temperature-related drift.
- Using a benchtop multimeter and pulsed power helps measure microamps/microvolts and reduce heating effects; cooling with non-conductive liquid like mineral oil is recommended.
- Computer interfacing via SCPI protocol over RS-232, USB, or Ethernet automates measurements, but the author's power supply lacked remote control, leading to purchasing a source measure unit (SMU).
- The Rohde & Schwarz NGU401 SMU, bought second-hand cheaply, supports FastLog mode for high-speed data streaming, though USB caused issues, so Ethernet was used instead.
- A C program captures diode V-I curves using FastLog, averaging data for accuracy across current ranges from microamps to amperes.
- Real plots reveal deviations from idealized exponential models in diodes due to resistive effects, and transistor behavior shows constant-current traits and nuanced breakdown voltages.
- To measure beyond the SMU's 20V limit, a series power supply and pulsed VGS signals were used to prevent transistor damage from heating.
Negative Resistance
12 hours ago
- Resistance is the opposition to current flow; in resistors, it is constant and follows Ohm's law (I = V/R).
- Differential resistance measures local response to small voltage changes and can be negative in certain V-I curve sections.
- True negative resistance (constant negative R) is impossible without an external power source, as it would imply energy generation.
- A practical circuit using an op-amp can simulate constant negative resistance by feeding current back into the source.
- Negative differential resistance (NDR) occurs when increasing voltage leads to decreasing current in part of the V-I curve.
- The lambda diode, made with two complementary JFETs, exhibits NDR without needing an external power supply.
- Snapback behavior is another form of NDR where increasing current causes a sudden drop in required voltage.

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Electronic Engineers Master Catalog

A Brief History of the Crazy Old 7-Segment Display

Tech note: making your own V-I plots at home

Negative Resistance