The British company Ferranti Ltd, which closed down in 1994 after over 100 years of operation, was an electrical engineering company with a long history of working on government and military contracts. They manufactured a large number of silicon transistors and diodes for use in such projects. Because of the secrecy surrounding such work, these components are less well-known than other UK manufacturers' semiconductors, although Ferranti databooks are not too hard to find.
In 1961 they established a 3000 sq ft laboratory devoted to proving the design and serviceability of silicon semiconductor devices in their Gem Mill factory at Chadderton, Oldham, Lancashire. However, I have several "Silicon Rectifiers" data sheets dated 1958. My main references are booklets "Silicon Semiconductor Devices" for 1962, 1963, and 1965, plus a few later data sheets. Most Ferranti semiconductors are painted black, and bear just a letter F to indicate the manufacturer, although a few do have the full name in the logo font. Ferranti devices are all silicon (with one exception), and nearly all use standardised encapsulation. They often bear two-letter codes that look like CV-series date codes, but cannot be.
This page only deals with Ferranti discrete transistors and diodes. They also made some early integrated circuits, which I do not describe here.
If you know anything about Ferranti's semiconductor history, or can explain their two-letter code, please
I do not possess all the devices below, in fact I am seeking many of them. It is noted in the text where I am seeking examples of any particular type: if you have some for sale or exchange, please Conversely, I am happy to help anyone looking for information on these devices. I have an extensive collection of original data sheets and books, and can provide some information on many Ferranti types.
I shall start this page with a conundrum and a plea for help. The device on the right is a Ferranti GD70, as evidenced by its box and also by a label on the small polythene packet that contained it. The seller believed that it is a semiconductor diode, because the 1963 CV Register lists the CV8380 as a 'semiconductor diode' having Ferranti GD70 as prototype. It is tempting to think that GD could mean 'germanium diode'. However I was suspicious because CV8380 is a high-numbered CV series type, and also, it does not look like a diode. Now I have obtained one and examined it closely, it looks even odder to me: the metal cylinder is hollow, and the central electrode penetrates into it. A test with a DVM reveals the device is open-circuit in both directions at the 9V applied by the DVM.
I'm now fairly sure that this is a gas-discharge tube of some kind. However, a number of questions remain:
- Why is GD70 called a semiconductor diode in the CV Register?
- Does anyone have a CV8380, or even just an image of one?
- What is the meaning of the circle symbol with vertical diameter line, on the box?
- Why does the device have no Ferranti branding? It has a red mark that could be that circle symbol again.
If you have any information about this device, please
The 'Ferranti Silicon Semiconductor Devices' booklet from January 1962 has two pages of silicon NPN transistors, grouped into 6 groups:
are a family of general-purpose low-power types in the SO-3/TO-5 outline, with two different Vce max values, and different gain banding. The image shows a ZT23 transistor.
are also in the general-purpose low-power group, this time in the SO-12/TO-18 outline, again with two different Vce max values, and different gain banding.
The image shows a box of unpainted ZT43 transistors.
If you have some for sale or exchange, please
The 'Ferranti Silicon Semiconductor Devices' booklet from December 1963 has expanded the transistor product set considerably:
General-purpose small signal types:
And the March 1965 booklet adds ZT87 to ZT89 and ZT110 to ZT119.
General-purpose medium-power and switching types:
And the March 1965 booklet adds ZT68.
Planar epitaxial high-speed switching types:
And the March 1965 booklet adds double transistor ZDT42 plus dual-emitter transistors ZDT30 and ZDT31.
And the March 1965 booklet adds ZT2015 and ZT2016.
High-power VHF transistors:
And the March 1965 booklet adds ZT3375.
Unipolar field-effect transistors:
And the March 1965 booklet adds ZFT16 and ZFT18.
The March 1965 booklet adds planar expitaxial bidirectional transistors:
If you have data on these devices, please
Because Ferranti were involved in many contracts with the UK military, it is not surprising that they produced many CV series devices. This is a box of CV7154 transistors date-coded 1964. The type CV7154 is equivalent to the ZT43 above. The 'Ferranti Silicon Semiconductor Devices' booklet from 1962 shows fifty-seven CV equivalents to Ferranti devices.
Ferranti silicon diode types are even more numerous than their transistors. I shall only list the earliest.
I have data sheets dated March 1958 for the ZR series of diffused junction rectifiers, in three groups:
The image shows ZR11 in its original carton printed "FERRANTI VALVE".
The image shows ZR20.
- ZR30C to ZR32C and reverse polarity versions have a max mean current of 18A when mounted on a 4-inch copper plate, considerably more when forced-air cooled
The 'Ferranti Silicon Semiconductor Devices' booklet from January 1962 has considerably expanded upon these and lists:
I also have a data sheet dated March 1958 for the ZS series of junction rectifiers:
These have a max mean dissipation of 150mW at 25 degrees C. The image shows ZS10A and ZS10B, this SO-1 outline is the commonest one for Ferranti low-power diodes.
The 'Ferranti Silicon Semiconductor Devices' booklet from January 1962 has re-classified the above as 100mA types and added several more series:
The 'Ferranti Silicon Semiconductor Devices' booklet from January 1962 has added three groups of "industrial power rectifiers":
I have a data sheet dated August 1958 for the KS series of Zener diodes:
The 'Ferranti Silicon Semiconductor Devices' booklet from January 1962 has superseded these by a wider range:
The 1962 booklet also includes types KS67 and KS68, unusual for their TO-5 outline, described as "voltage reference packs". They are "extremely stable zener voltage reference sources with very low temperature coefficient".
The 1962 booklet also includes a high-power range of "voltage regulators:
I have a data sheet dated January 1959 for the ZC series of variable capacitance diodes:
The 'Ferranti Silicon Semiconductor Devices' booklet from January 1962 also includes:
The image shows the large HS32 high-voltage rectifier.