The breadth of functions delivered by integrated circuits today is truly impressive, making it rare to come across simple small-signal transistor projects featured in electronics publications. However, if you delve back into the roots of solid-state electronics, you’ll discover a host of clever ways engineers maximized the potential of the most basic active components.
Back then, everyone was familiar with transistor part numbers and their characteristics. For electronics enthusiasts in Europe, there was likely one transistor that stood out above all others and frequently found its way onto workbenches. ElectronicsNotes takes a closer look at the OC71, probably the most common PNP germanium transistor used across the Atlantic at the time this article is being written.
Launched in 1953, the OC71 appeared only a few years after the transistor itself was invented. While its specifications may seem modest and pedestrian by today’s standards, they represented a significant leap forward in performance back then. The article also touches on issues such as thermal runaway, which commonly affected germanium devices, and explains the use of black silicone filling to reduce their sensitivity to light.
Exploring components like the OC71 not only highlights the evolution of transistor technology but also provides valuable insight into the ingenuity of early solid-state electronics design.
https://hackaday.com/2025/10/29/all-hail-the-oc71/
