BC549C Transistor

The BC549C is an NPN transistor belonging to a group of general-purpose NPN semiconductors consisting of BC547, BC548, and BC549. These transistors are used in audio frequency, and small signal directly coupled preamplifiers. The general-purpose range of transistors is a good substitute for basic non-critical audio applications, as these transistors are similar and equivalents to each other.

These transistors are the direct modern equivalent replacements to the earlier BC107, BC108, and BC109. The most noticeable difference is in the packaging and pin configuration. The BC109 package was TO-18 / SOT18 metal canister, whilst the modern BC549 package is a TO-92 / SOT54 plastic material.

Pinout

The pin configuration is very simple and is collector, base, emitter.

Transistor Symbol

The image above shows the transistor symbol for an NPN component.

Complementary Transistor

The BC549 is an NPN transistor; however, it also has a complementary PNP version, which is the BC559. The complementary version has identical characteristics except it is a PNP type. This is very useful for building symmetrical push-pull preamplifier stages.

Circuit

Here is a typical audio amplifier circuit using biasing resistors, and an LT700 output transformer.

The Difference between BC548 and BC549

The BC548 and BC549 are almost identical NPN transistors, and they both have an absolute maximum collector rating of 100 mA, and power dissipation of 500 mW. Both transistors have a maximum collector-emitter rating of 30 V, and collector-base rating of 30 V. The main difference is that BC549 is a special low-noise type and available in groups B and C only, whilst BC548 is more general-purpose type and available in all three groups A, B, and C.

Equivalent Replacement

Due to the similarities between a BC548 and BC549, they are interchangeable within many low voltage non-critical circuits, and therefore considered equivalents. As early as 1979, Ferranti Semiconductors were manufacturing the ZTX107, ZTX108, and ZTX109 transistors which were direct equivalent replacementa for the Philips BC series. The ZTX series came in an E-Line (TO-92) package formed by injection moulding silicone plastic to provide a rugged encapsulation.