Mullard Limited was a British manufacturer of electronic components. The Mullard Radio Valve Co. Ltd. of Southfields, London, was founded in 1920 by Captain Stanley R. Mullard, who had previously designed thermionic valves for the Admiralty before becoming managing director of the Z Electric Lamp Co. The company soon moved to Hammersmith, London and then in 1923 to Balham, London. The head office in later years was Mullard House at 1-19 Torrington Place, Bloomsbury, now part of University College London.
In 1923, to meet the technical demands of the newly formed BBC, Mullard formed a partnership with the Dutch manufacturer Philips. The valves (vacuum tubes) produced in this period were named with the prefix PM, for Philips-Mullard, beginning with the PM3 and PM4 in 1926. Mullard finally sold all its shares to Philips in 1927. In 1928 the company introduced the first pentode valve to the British market.
Mullard opened a new manufacturing plant at the end of New Road, Mitcham, Surrey in 1929. A second building was added in 1936. Both buildings had a very distinctive flat roof construction and were very similar to those at Philips' headquarters in Eindhoven, Netherlands. Co-sited with the Mullard buildings was the manufacturing complex for Philips Radios. Mitcham was also home to the Mullard Application Laboratory.
In the late 1930s Mullard opened a new plant in Blackburn, Lancashire. By 1949 Mullard had produced a number of television sets, such as the MTS-521 and MTS-684. In 1951 Mullard was producing the LSD series of photographic flash tubes.
Mullard had factories in Southport and Simonstone, near Padiham both in Lancashire. The latter closed in 2004. There was also a sister factory at Belmont in Durham (closed in June 2005). Other factories included those at Fleetwood (closed in 1979) and Lytham St. Annes (closed in 1972). A feeder factory at Haydock closed in 1981. A small factory in Hove closed in the early 1970s.
Mullard owned semiconductor factories in Southampton and Stockport. Both sites were later owned by NXP Semiconductors (formerly Philips Semiconductors). The Southampton site is now closed. The one in Hazel Grove, Stockport specialises in power semiconductor devices and is now Nexperia Manchester.
The first transistors produced by Mullard were the OC50 and OC51 point-contact types in 1952, which were not widely used. In 1953 Mullard moved to junction transistors, beginning with the plastic-cased OC10 series. These were followed by the glass-encapsulated OC43...47, OC70/71, (released in 1957) and OC80 series (the output devices were metal encapsulated to facilitate heatsinking), which were produced in large numbers and copied by other companies, such as Valvo (another Philips subsidiary) and Siemens in Germany, and Amperex in the USA. RF transistors were the OC170 and OC171. All these were germanium PNP transistors. Mullard's first silicon transistors were the OC201 to OC207, PNP alloy types using the standard SO-2 metal-over-glass construction such as the OC201 shown. From about 1960 Mullard switched to using the BC prefix for silicon, and AC for germanium, eliminating the confusion of part numbers. in the mid 1960s the first plastic packages were introduced. In 1964 the company produced a prototype electronic desktop calculator as a technology demonstrator for its transistors and cold cathode indicator tubes.
In 1957 Philips-Mullard helped to set up the Mullard Radio Astronomy Observatory (MRAO) at the University of Cambridge. In 1966 the Mullard Space Science Laboratory (MSSL) was opened near Dorking, Surrey as part of University College London. The Royal Society Mullard Award for young scientists and engineers was set up in 1967.
Philips continued to use the brand name "Mullard" in the UK until 1988. Mullard Research Laboratories in Redhill, Surrey then became Philips Research Laboratories. As of 2007, the Mullard brand has been revived by Sovtek, producing a variant of the ECC83 and EL34.
The Z Electric Lamp Co. continued business into the 1970s operating from premises in Thornton Heath, South London, manufacturing lamps of specialised design. However, it closed due to the recession in the mid 1970s.