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.

BC108 family transistors from various manufacturers (ITT, CEMI, ATES, Siemens)

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	Ptot	Polarity	≥ 70 VCBO ≥ 64 VCEO	50 VCBO	30 VCBO	Low-Noise (<4 dB) 30 VCBO	Low-Noise (<4 dB) 50 VCBO	Notes/Source
TO-18 (C-B-E) Emitter is closest to tab	300 mW	NPN	BC190 64 VCEO	BC107 BC107A BC107B 45 VCEO	BC108 BC108A BC108B BC108C 20 VCEO	BC109 BC109B BC109C 20 VCEO		Philips Semiconductor Handbook Oct 1966
		PNP		BC177 45 VCEO	BC178 25 VCEO	BC179 25 VCEO		Philips Application Book: Audio Amplifier Systems, 1971
Lockfit (C-B-E)	250 mW	NPN		BC147 45 VCEO	BC148 20 VCEO	BC149 20 VCEO		a discontinued plastic case with leads that locks into a PCB's holes.
		PNP		BC157 45 VCEO	BC158 25 VCEO	BC159 20 VCEO
TO92B (E-C-B)	300 mW	NPN		BC167 45 VCEO	BC168 20 VCEO	BC169 20 VCEO
		PNP		BC257 45 VCEO	BC258 25 VCEO	BC259 20 VCEO		(Also: BC256 64 VCBO)
TO92F (C-B-E)	300 mW*	NPN	BC174 64 VCEO	BC171 BC237 45 VCEO	BC172 BC238 20 VCEO	BC173 BC239 20 VCEO		*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).
		PNP		BC307 45 VCEO	BC308 25 VCEO	BC309 20 VCEO
TO92A (E-B-C)	310 mW	NPN		BC317 45 VCEO	BC318 30 VCEO	BC319 20 VCEO		Note: 150 mA rating; BC318 VCBO 40 V to 45 V
		PNP		BC320 45 VCEO	BC321 30 VCEO	BC322 20 VCEO
TO92F (C-B-E)	500 mW*	NPN	BC546 65 VCEO	BC547 45 VCEO	BC548 30 VCEO	BC549 30 VCEO	BC550 45 VCEO	from Mullard 1977 and Fairchild 2001 specifications; *Some manufacturers specify a 625 mW rating
		PNP	BC556 65 VCEO	BC557 45 VCEO	BC558 30 VCEO	BC559 30 VCEO	BC560 45 VCEO
SOT-23	150 mW	NPN	BC846 65 VCEO	BC847 45 VCEO	BC848 30 VCEO	BC849 30 VCEO	BC850 45 VCEO	Surface-mount
		PNP	BC856 65 VCEO	BC857 45 VCEO	BC858 30 VCEO	BC859 30 VCEO	BC860 45 VCEO

(See also: [1] 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.

See also

• 2N2222, 2N2907
• 2N3904, 2N3906
• 2N3055
• BC548
• KT315

Further reading

• BC Transistor Substitution Tables

Historical Databooks

• Small-Signal Transistor Data Book, 1386 pages, 1984, Motorola.
• Transistor and Diode Data Book, 1236 pages, 1973, Texas Instruments.