Philco MADT Transistor from the Late 1950s


Micro Alloy Diffused base germanium transistor 2N501 from the late 1950s. Philco invented a diffusion and chemical etching process which thinned the base region of alloy junction transistors producing very fast switching speed devices. 
The process was subsequently licensed to other transistor companies including Semiconductors Limited (Semics) of Swindon in the UK.

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