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A OC170 germanium PNP alloy junction transistor in TO1 metal case. These were a common transistor in the 1960s for RF and IF stages. This package is noted for a fourth 'shield' connection to the case. These transistors are now decades old and most have failed from the formation of internal metal crystalisation known as 'whiskers' that cause short circuits.

The idea[]

Creating a small, cheep and durable replacement for valves (vacuum tubes).


The then standard silicon\germanium etching process.


Mullard OC170 germanium PNP alloy junction transistor.
Category. Statistic.
Designed in. Mid 1950s.
Made in. Late 1950s.
Transistors per chip. 1.
Power supply. Low and battery power.
Still in use. Retired in the late 1960s.
Nationality. Dutch invented, later perfected and also manufactured by the British.

The breakdown voltage of about 20V, maximum collector current of 10mA, was about 60MHz and the Beta is typically 150. It was one of UK's  and Netherlands's first moves in to the modern electrical business and it was seen as a national icon at the time.


A small TO-1 metal 'can' (AKA 'the can' or 'transistor can') filled with resin or glass. It has 4 metal legs, one of which was a anti-static build up 'shield' wire.

Also see[]


  1. http://w140.com/OC170.pdf
  2. http://w140.com/tekwiki/wiki/OC170
  3. https://sites.google.com/site/transistorhistory/Home/european-semiconductor-manufacturers/philips
  4. https://reverb.com/item/502396-1958-mullard-gold-saucer-oc44-pnp-germanium-transistors-rangemaster-pedal-kings
  5. https://images.search.yahoo.com/search/images;_ylt=A0LEV1oZo2lXTIQACsdXNyoA;_ylu=X3oDMTEyY3M1aWxwBGNvbG8DYmYxBHBvcwMxBHZ0aWQDVUkyQzJfMQRzZWMDc2M-?p=Mullard+OC170&fr=yset_chr_cnewtab
  6. https://reverb.com/item/127295-nos-new-old-stock-mullard-black-glass-oc44-pnp-germanium-transistors-tested/similar
  7. http://www.ebay.co.uk/sch/i.html?_nkw=mullard+oc