# BC108 family

The BC107, BC108 and BC109 are general-purpose low power silicon NPN bipolar junction transistors found very often in equipment and electronics books/articles from Europe, Australia and many other countries from the 1960s. They were created by Philips and Mullard in 1963 and introduced in April 1966. Initially in metal (TO-18) packages, the range expanded over time to include other package types, higher voltage ratings, and a better selection of gain (h$_{FE}$ and h$_{fe}$) groupings, as well as complementary PNP types. Some manufacturers have specified their parts with a higher power dissipation rating (P$_{tot}$) than others.
The BC548 is an example of the modern low-cost member of this family, still in a through-hole package, while the BC848 is the surface-mount version.

## Table of BC107 to BC860 variants

| Case | P$_{tot}$ | Polarity | ≥ 70 V$_{CBO}$ ≥ 64 V$_{CEO}$ | 50 V$_{CBO}$ | 30 V$_{CBO}$ | Low-Noise (<4 dB) 30 V$_{CBO}$ | Low-Noise (<4 dB) 50 V$_{CBO}$ | Notes/Source |
| TO-18 (C-B-E) Emitter is closest to tab | 300 mW | NPN | BC190 64 V$_{CEO}$ | BC107 BC107A BC107B 45 V$_{CEO}$ | BC108 BC108A BC108B BC108C 20 V$_{CEO}$ | BC109 BC109B BC109C 20 V$_{CEO}$ | | Philips Semiconductor Handbook Oct 1966 |
| TO-18 (C-B-E) Emitter is closest to tab | 300 mW | PNP | | BC177 45 V$_{CEO}$ | BC178 25 V$_{CEO}$ | BC179 25 V$_{CEO}$ | | Philips Application Book: Audio Amplifier Systems, 1971 |
| Lockfit (C-B-E) | 250 mW | NPN | | BC147 45 V$_{CEO}$ | BC148 20 V$_{CEO}$ | BC149 20 V$_{CEO}$ | | a discontinued plastic case with leads that locks into a PCB's holes. |
| Lockfit (C-B-E) | 250 mW | PNP | | BC157 45 V$_{CEO}$ | BC158 25 V$_{CEO}$ | BC159 20 V$_{CEO}$ | | a discontinued plastic case with leads that locks into a PCB's holes. |
| TO92B (E-C-B) | 300 mW | NPN | | BC167 45 V$_{CEO}$ | BC168 20 V$_{CEO}$ | BC169 20 V$_{CEO}$ | | |
| TO92B (E-C-B) | 300 mW | PNP | | BC257 45 V$_{CEO}$ | BC258 25 V$_{CEO}$ | BC259 20 V$_{CEO}$ | | (Also: BC256 64 V$_{CBO}$) |
| TO92F (C-B-E) | 300 mW* | NPN | BC174 64 V$_{CEO}$ | BC171 BC237 45 V$_{CEO}$ | BC172 BC238 20 V$_{CEO}$ | BC173 BC239 20 V$_{CEO}$ | | *Fairchild's power rating is 500 mW Some devices have pre-formed leads with the base bent backwards like a TO-18 pinout (e.g. MEL). |
| TO92F (C-B-E) | 300 mW* | PNP | | BC307 45 V$_{CEO}$ | BC308 25 V$_{CEO}$ | BC309 20 V$_{CEO}$ | | *Fairchild's power rating is 500 mW Some devices have pre-formed leads with the base bent backwards like a TO-18 pinout (e.g. MEL). |
| TO92A (E-B-C) | 310 mW | NPN | | BC317 45 V$_{CEO}$ | BC318 30 V$_{CEO}$ | BC319 20 V$_{CEO}$ | | Note: 150 mA rating; BC318 V$_{CBO}$ 40 V to 45 V |
| TO92A (E-B-C) | 310 mW | PNP | | BC320 45 V$_{CEO}$ | BC321 30 V$_{CEO}$ | BC322 20 V$_{CEO}$ | | Note: 150 mA rating; BC318 V$_{CBO}$ 40 V to 45 V |
| TO92F (C-B-E) | 500 mW* | NPN | BC546 65 V$_{CEO}$ | BC547 45 V$_{CEO}$ | BC548 30 V$_{CEO}$ | BC549 30 V$_{CEO}$ | BC550 45 V$_{CEO}$ | from Mullard 1977 and Fairchild 2001 specifications; *Some manufacturers specify a 625 mW rating |
| TO92F (C-B-E) | 500 mW* | PNP | BC556 65 V$_{CEO}$ | BC557 45 V$_{CEO}$ | BC558 30 V$_{CEO}$ | BC559 30 V$_{CEO}$ | BC560 45 V$_{CEO}$ | from Mullard 1977 and Fairchild 2001 specifications; *Some manufacturers specify a 625 mW rating |
| SOT-23 | 150 mW | NPN | BC846 65 V$_{CEO}$ | BC847 45 V$_{CEO}$ | BC848 30 V$_{CEO}$ | BC849 30 V$_{CEO}$ | BC850 45 V$_{CEO}$ | Surface-mount |
| SOT-23 | 150 mW | PNP | BC856 65 V$_{CEO}$ | BC857 45 V$_{CEO}$ | BC858 30 V$_{CEO}$ | BC859 30 V$_{CEO}$ | BC860 45 V$_{CEO}$ | Surface-mount |
(See also: for a neat summary of some of the family).
Noise figure (at 1 kHz, for a 2 kilohm source, BW = 200 Hz, I$_C$=0.2 mA/V$_{CE}$=5 V) is <10 dB for those not tabulated as "Low Noise".

## Current ratings

All types have a maximum collector current of 100 mA, except that the original Philips tentative data dated 4.4.1966 specified a maximum collector current of 100 mA peak (I$_{CM}$) for the BC107/8/9, and Telefunken originally specified a maximum collector current of 50 mA for the BC109, but since at least 1973 all have revised collector currents of 100 mA average or 200 mA peak, except that the BC317-BC322 range have a 150 mA (continuous) rating.

## A, B and C gain groupings

The above devices' type numbers may be followed by a letter "A" to "C" to indicate low to high gain (h$_{FE}$) groups (see BC548 Gain groupings).

## Other characteristics

Transistors in this family:
* require a base-emitter voltage (V$_{BE(on)}$) in the range of 0.55 to 0.7 volts for a collector current of 2 mA when the Collector voltage is 5 volts.
* Will have a saturation voltage (V$_{CE(sat)}$) of at most 0.2 volts (typically 0.07 volts) at a collector current of 10 mA and a base current of 0.5 mA (when the base voltage is typically 0.73 volts; 0.83 volts maximum).
* Has greater than unity current gain up to a frequency (f$_T$) of at least 150 MHz, typically 250 MHz, at a collector current of 10 mA (typically 85 MHz and a collector current of 0.5 mA)
* These transistors can be found in the list of suitable TUN transistors ("Transistor Universal Npn") by the [Elektor] magazine for their circuits that require general purpose Silicon transistors meeting certain minimum standards.
* These transistors have PNP complementary types, with only the second digit changed (to a number normally greater than 4) to indicate the reversed polarity, e.g. a BC177 is PNP version of the BC108, and a BC559 is a PNP version of a BC549.
* Note that this "family" of transistors do not include every transistor with a type number beginning "BC" and ending in "7", "8" or "9". For example, the BC328 and BC338 transistors are not included in the Elektor list (and not "family" members), despite sharing some similarities.