Popular transistors.

BC547A transistor.

Marking: BC547A.
Package: TO-92, 1-collector, 2-base, 3-emitter.
Material of transistor: Si
Polarity: NPN
Total Devise power dissipation |PD|: 0.625 W(at ambient temperature ≤ + 25 )
Collector-base breakdown voltage |VCBO|: 50V
Collector-emitter breakdown voltage |VCEO|: 45V
Emitter-base breakdown voltage |VEBO|: 6V
Maximum collector current |Ic max|: 0.1A
Maximum junction temperature |Tj|: +150 C
Transition frequency (ft) : 300MHz
Input Capacitance |Cib|:9pF
Output Capacitance |Cob|:6pF
Collector-emitter saturation voltage|VCE|:
Base-emitter saturation voltage|VBE|:
Forward current transfer ratio |hFE|:
Turn-on time|t on |:35ns
Turn-off time |t off |:300ns
Noise Figure, (NF): 2-10dB

The complementary p-n-p transistor to the BC547A is the BC557A.
Instead of a transistor BC547A, you can use BC546 or BC550, BC847(SOT23) as its equivalent.

Ratings and characteristics curves.

BC546, BC547, BC548.
Collector-base capacitance,
Emitter-base capacitance
versus reverse bias voltage(Tamb=25 C).

BC546, BC547, BC548.Ratings and characteristics curves.Collector-base capacitance,Emitter-base capacitance versus reverse bias voltage.

BC546, BC547, BC548.
Gain-bandwidth product
versus collector current(Tamb=25 C,VCE=10V).

BC546, BC547, BC548.Ratings and characteristics curves.Gain-bandwidth product versus collector current.

BC546, BC547, BC548.
Relative h-parameters
versus collector current(Tamb=25 C,VCE=5V).

BC546, BC547, BC548.Ratings and characteristics curves.Relative h-parameters versus collector current.

BC546, BC547, BC548.
Base-Emitter Saturation Voltage(VBE)
Collector-Emitter Saturation Voltage (VCE).

BC546, BC547, BC548..Base-Emitter Saturation Voltage. Collector-Emitter Saturation Voltage.

BC546, BC547, BC548..Transfer Characteristic.

BC546, BC547, BC548..Transfer Characteristic.

BC546, BC547, BC548.Static Characteristic.

BC546, BC547, BC548..Static Characteristic.

Example of application.

BC546, BC547, BC548 transistors are very popular in the world.
You can use them:
1. In the audio-frequency amplifiers.
For example: mini-amplifier with push - pull output.

BC547,BC557 in amplifier with push-pull output

Resistors: R1-1 MOm, R2-56 KOm, R3-1 KOm, R4-240 Om,
R5-220 KOm.
Capacitors: C1-1 µF, C2-5 µF, C3-47 nF, C4,C5-100 µF*12V.
Transistors: Q1, Q4 - BC546, BC547, BC548; Q2, Q3 - BC557.

2.Radio-frequency amplifiers(in transistor radio AM).
BC547,BC557 in transistor radio AM

Resistors: R1, R4 - 220* KOm, R2 - 75* KOm,
R3, R5 - 10 KOm, R6 - 56 KOm, R7 - 12 KOm, R8 - 870 Om.
Capacitors:variable C1 - 20-415pF, C2 - 10 nF, C3 - 100nF,
C4 - 5 µF*6V.
Transistors: Q1, Q2, Q3, Q4 - BC546, BC547, BC548;
Q5 - BC557.
Loopstick antenna L1 - 60 turns wire 0,25mm
wrapped around 10mm ferrite rod;

3. In Radio-frequency oscillators(in transistor radio FM.)
BC547,BC557 in transistor radio FM

Variable resistor - 10 KOm.
Capacitors:variable C1 - 5-35pF, C2 - 5-14 pF, C3 - 0,1 µF,
C4 - 10 pF.
Coils: L1-8,5 and L2-2,5 turns diam 6mm;
L3, L4, L5 - 8 turns diam 8mm.
Transistor - BC546, BC547, BC548.