Highfields Amateur Radio Club
Constructors Corner.

Most diode and transistor markings follow one of these codes: JEDEC, JIS or Pro-Electron.

For Integrated Circuits (ICs, "Chips"), look for known numbers (e.g. 741, 4001, 7400) between the prefix and any suffix. Don't confuse it with the date code. ICs typically have two numbers, the part number and the date code.

1. Joint Electron Device Engineering Council (JEDEC)

These part numbers take the form: digit, letter, sequential number, suffix (if any).

The letter is always "N", and the first digit is 1 for diodes, 2 for transistors, 3 for four-leaded devices, and so forth. 4N and 5N are reserved for opto-couplers. The sequential numbers run from 100 to 9999 and indicate the approximate date the device was first made.

If present, a suffix could indicate various things. For example, a 2N2222A is an enhanced version of a 2N2222. It has higher gain, frequency, and voltage ratings. Always check the manufacturers data sheet.

Examples: 1N914 (diode), 2N2222, 2N2222A, 2N904 (transistors).

NOTE: When a metal-can version of a JEDEC transistor is re-made in a plastic package, it is often given a number such as PN2222A which is a 2N2222A in a plastic case.

2. Japanese Industrial Standard (JIS)

These part numbers take the form: digit, two letters, sequential number, suffix (if any).

Digits are 1 for diodes, 2 for transistors, and so forth. The letters indicate the type and intended application of the device according to the following code:

• SA: PNP High Frequency Transistor.
• SB: PNP Audio Frequency Transistor.
• SC: NPN High Frequency Transistor.
• SD: NPN Audio Frequency Transistor.
• SE: Diode.
• SF: Thyristor.
• SG: Gunn device.
• SH: UniJunction Transistor .
• SJ: P-channel Field Effect Transistor.
• SK: N-channel Field Effect Transistor.
• SM: Triac.
• SQ: Light Emitting Diode.
• SR: Rectifier.
• SS: Signal diode.
• ST: Avalanche diode.
• SV: Varicap.
• SZ: Zener diode.

The sequential numbers run from 10-9999. The optional suffix indicates that the type is approved for use by various Japanese organizations. Since the code for transistors always begins with 2S, it is sometimes omitted; for example, a 2SC733 could be marked C733.

Examples: 2SA1187, 2SB646, 2SC733.

3. Pro-Electron (European)

These part numbers take the form: two letters, letter (optional), sequential number, suffix (if any).

The first letter indicates the material:

• A = Ge (Germanium).
• B = Si (Silicon).
• C = GaAs (Gallium arsenide).
• R = compound of materials.

The second letter indicates the device type and intended application:

• A: diode, Radio Frequency.
• B: diode,varactor.
• C: transistor, Audio Frequency, small signal.
• D: transistor, Audio Frequency, power.
• E: Tunnel diode.
• F: transistor, High Frequency, small signal.
• K: Hall effect device.
• L: Transistor, High Frequency, power.
• N: Opto-coupler.
• P: Radiation sensitive device.
• Q: Radiation producing device.
• R: Thyristor, Low power.
• T: Thyristor, Power.
• U: Transistor, power, switching.
• Y: Rectifier.
• Z: Zener, or voltage regulator diode.

The third letter indicates if the device is intended for industrial or commercial applications. It's usually a W, X, Y, or Z. The sequential numbers run from 100-9999.

Examples: BC108A, BAW68, BF239, BFY51.

Note: For all types.

Instead of 2N and so forth, some manufacturers use their own system of designations. Some common prefixes are:

• MJ: Motorola power, metal case
• MJE: Motorola power, plastic case
• MPS: Motorola low power, plastic case
• MRF: Motorola HF, VHF and microwave transistor
• RCA: RCA device
• TIP: Texas Instruments (TI) power transistor, plastic case
• TIPL: TI planar power transistor
• TIS: TI small signal transistor (plastic case)
• ZT: Ferranti
• ZTX: Ferranti

Examples: ZTX302, TIP31A, MJE3055.

Many manufacturers also make custom parts, or custom-label standard parts, for large volume OEM customers. Typically, they have the OEM's mark or logo and part-number. When such parts hit the surplus market, they end up in hobbyist "bargain packs". Since data on these devices is not usually available, they are best used as LED-drivers and other such applications where the actual specifications are not critical.