Editing Pro Electron (section)

== Designation system ==
Examples of Pro Electron type designators are:
* AD162        – Germanium power [[transistor]] for audio frequency use
* BY133        – [[Silicon rectifier]]
* BZY88C5V1    – Silicon 5.1 volt [[Zener diode]]
* CQY97        – [[light emitting diode]]
* ECC83        – 6.3 volt heater noval dual triode
* A63EAA00XX01 – Color TV picture tube
* SAA1300      – Digital integrated circuit

Pro Electron took the popular European coding system in use from around 1934 for valves ([[Vacuum tube|tubes]]), i.e. the [[Mullard–Philips tube designation]], and essentially re-allocated several of the rarely used heater designations (first letter of the part number) for semiconductors. The second letter was used in a similar way to the valves naming convention: "A" for signal diode, "C" for low-power bipolar transistor or triode, "D" for high-power transistor (or triode), and "Y" for rectifier, but other letter designations did not follow the vacuum tube mode so closely.

The three digits (or letter followed by two digits) after the first two letters were essentially a sequence number, with (at first) a vestige of the valve-era convention that the first one or two digits would indicate the base (package) type in examples such as in this family of general-purpose transistors:
{| class="wikitable"
|-
! Package !! NPN !! PNP
|-
| [[TO-18]]  || BC10x || BC17x
|-
| [[Lockfit]] || BC14x || BC15x
|-
| [[TO-92]] || [[BC548|BC54x]] || BC55x
|}
... where x may be:
* 7 for high voltage
* 8 for general purpose
* 9 for low noise/high gain

Pro Electron naming for transistors and Zener diodes has been widely taken up by semiconductor manufactures around the world. Pro Electron naming of [[integrated circuits]], other than some special (e.g. television signal-processing) chips, did not greatly take hold (even in Europe). Other popular designation systems were used for many integrated circuits.

===Differences between Pro Electron and earlier valve-naming conventions ===

* Unlike the tube naming convention, if there are two transistors in a single envelope, the type letter was never repeated - so a dual NPN RF transistor might get a type "BFM505" rather than something like "BFF505" for instance. 
* Although some of the most popular devices conform to a pattern of serial numbers that identified package type and polarity, many do not.
* The letters assigned for the second character of transistor and diode type numbers differ in several ways, e.g.
** "B" tends to be used for dual ''varicap'' diodes
** "L" in the context of transistors designates RF power (transmitting) transistors; for valves it meant a high-power pentode tube (the usual choice for power RF)
** "Z" is used for semiconductor Zener diodes instead of (full-wave) rectifier valves ([[Vacuum tube|tubes]]).

=== Frequently used first letters in European active devices ===

**'''A''' [[Germanium]] (or any semiconductor with junctions in a material with a band gap of 0.6 to 1.0eV)
**'''B''' [[Silicon]] (or band gap of 1.0 to 1.3eV)
**'''C''' [[Boron group|III]]-[[Nitrogen group|V]] semiconductors with a band gap of 1.3eV or more, like [[gallium arsenide]] in [[Light-emitting diode|LED]]s
**'''D''' may be...
***Semiconductors with a [[band gap]] less than 0.6eV, such as [[indium antimonide]] in [[infrared detector]]s (rarely used), '''or'''
***(Mullard–Philips) 1.4V (or less) filament tubes
**'''E''' (Mullard–Philips) tubes with a 6.3V heater
**'''F''' Digital integrated circuits
**'''P''' (Mullard–Philips) tubes for a 300mA series heater supply
**'''R''' Devices without junctions, e.g. [[cadmium sulfide]] in a [[photoresistor]]
**'''S''' Solitary digital integrated circuits
**'''T''' Linear integrated circuits
**'''U''' may be...
*** (Mullard–Philips) tubes for a 100mA series heater supply, '''or'''
*** Mixed digital/analogue integrated circuits