The BC547 is an NPN transistor belonging to a group of general-purpose NPN semiconductors. This transistor series further divides into three groups consisting of BC547A, BC547B, and BC547C, according to the current gain.
Here is an image showing the pin configuration of this transistor in case type TO-92. These transistors are available in SOT54 case type as well. Most of these modern transistors utilise a plastic package.
NPN Transistor Symbol
Here is the symbol for the transistor showing the orientation of the emitter junction.
The BC547, BC548, and BC549 are a group of general-purpose transistors with similar electrical characteristics. For basic and simple low voltage audio applications, they are almost equivalents. The BC548 and BC549 are very similar to the BC547 in every respect apart from a difference in operating breakdown voltages.
BC547 has a 50 V rating for Vcbo and Vces, and 45 V for Vceo. The BC546 has an 80 V rating for Vcbo and Vces, and 65 V for Vceo.
Current Gain Groups A, B, C
With Vce at 5 V, and Ic at 10 uA, the current gain (hFE) for A is 90, B is150, C is 270.
With Vce at 5 V, and Ic at 2 mA, the current gain (hFE) for A is 180, B 290, C is 500.
With Vce at 5 V, and Ic at 100 mA, the current gain (hFE) for A is 120, B 200, C is 400.
The maximum useful attainable hFE is 500 in the group C version, which is the BC547C transistor.
The absolute maximum current this transistor can handle is 100 mA. This is the DC current rating. The peak current rating is 200 mA.
The PNP equivalent is the complimentary transistor, which is the BC557. This is identical in every respect to the NPN type, except that it is a PNP type. The complimentary transistor is very useful for symmetrical push-pull amplifier circuits.
Typical applications include audio amplification and small signal circuits. It has a transition frequency range up to 100 MHz.
When using the transistor as a switch, the max current rating poses a limit on the type of loads that it can drive. This transistor has a max collector rating of 100 mA which is enough to drive an LED circuit, or an LDR circuit, or a NOT gate. In addition, this transistor can switch low current Arduino microcontroller circuits, and even a low current micro relay.
BC547 Vs BC548
For the most part, both transistors are the same. They have the same maximum collector rating of 100 mA, and a peak collector rating of 200 mA. They both have the same power dissipation rating of 500 mW.
For the hFE current gain, both transistors are available in all three groups A, B, and C. Hence that is identical as well.
The main difference is in the maximum breakdown voltages. For BC548 Vcbo, Vces, and Vceo, are rated at 30 V, and Veb is 5 V. For BC547 Vcbo, and Vces are rates at 50 V. Vceo is 45 V, and Vebo is 6V.
Related ArticlesTransistor as a Switch Using LDR
Transistor Circuit to Drive LED
Transistor as a Switch for Relay