A Planet Analog article, “2N3904: Why use a 60-year-old transistor?” by Bill Schweber, inspired some interest in this old transistor and how it’s commonly used, and if any uncommon uses might exist.

Repeated or prolonged pressing of a doorbell can be disruptive, particularly in homes or offices. Visitors often press the bell multiple times in quick succession or hold it down too long, creating ...

The FlippenHeimer is a compact Geiger counter add-on module designed to work with the Flipper Zero. It allows users to monitor beta and gamma radiation levels using the Flipper’s display and power ...

A friend recently sent me an email noting that the classic 2N3904 bipolar transistor was now 60 years old. Since its “birth” was before I got involved with basic electronics, that callout was ...

When measuring distortion in audio devices, it makes sense to filter out the controlling sinusoidal signal before the spectrum analyzer. This is particularly easy with this notch filter, as the notch ...

If frequencies and/or times have to be recorded in complex measurement setups and the results have to be related to each other accurately and, above all, precisely, in terms of time, these measuring ...

Abstract: In this paper, we have designed a Chaotic Colpitt's oscillator using transistor 2N3904. The circuit simulation using Multisim 2001 is also presented. The simulation results show that Colpitt ...