ONSEMI BC556 PNP Epitaxial Silicon Transistor Specs & Datasheet

FREE-SKY (HK) ELECTRONICS CO.,LIMITED / 12-02 17:50

The BC556 is a versatile PNP epitaxial silicon transistor. This article will discuss the BC556’s key specifications, pin configuration, equivalent models and replacement notes, typical circuit roles and more.

Catalog

1. BC556 Transistor Overview

2. BC556 Gain Groups

3. BC556 Transistor Equivalents

4. BC556 Pinout Configuration

5. BC556 Transistor Specifications

6. BC556 Transistor Features

7. BC556 Transistor Advantages

8. BC556 Transistor Working in Circuit

9. BC556 Transistor Applications

10. Comparison: BC556 vs BC557BTA

11. BC556 Mechanical Dimensions

12. Manufacturer

BC556 Transistor Overview

The BC556 is a PNP epitaxial silicon transistor designed for general-purpose low-noise amplification and switching. With a –65 V collector-emitter rating, 100 mA collector current, and a wide gain range. Its TO-92 package makes it easy to integrate into compact designs while maintaining stable operation across common voltage levels.

If you are interested in purchasing the BC556, feel free to contact us for pricing and availability.

BC556 Gain Groups

The gain groups of the BC556 are important because they let you choose the right amplification level for your circuit. Lower-gain versions offer stable switching, medium-gain types provide balanced performance, and high-gain versions are ideal for sensitive or low-noise signal stages. Selecting the proper gain group ensures accurate biasing and optimal circuit performance.

Gain Group	Suffix	hFE Range	Notes
Low Gain	BC556A	110 – 220	Suitable for general switching and basic amplification.
Medium Gain	BC556B	200 – 450	Most common choice; balanced noise and amplification.
High Gain	BC556C	420 – 800	Best for low-noise audio and sensitive preamp stages.

BC556 Transistor Equivalents

Model	Type	VCEO (Collector-Emitter Voltage)	IC Max	hFE Range	Package
BC557	PNP	–45 V	100 mA	110–800	TO-92
BC558	PNP	–30 V	100 mA	110–800	TO-92
2N3906	PNP	–40 V	200 mA	100–300	TO-92
2N4403	PNP	–40 V	600 mA	100–300	TO-92
A1015	PNP	–50 V	150 mA	70–400	TO-92
S8550	PNP	–25 V	700 mA	85–300	TO-92
BC857	PNP (SMD)	–45 V	100 mA	110–800	SOT-23

BC556 Pinout Configuration

Pin Number	Pin Name	Description
1	Collector	Current flows from emitter to collector when the transistor is ON (PNP).
2	Base	Controls the transistor’s switching and amplification.
3	Emitter	Current flows out of the emitter; connected to the more positive voltage in PNP circuits.

BC556 Transistor Specifications

Absolute Maximum Ratings

Parameter	Symbol	Value	Unit
Collector–Base Voltage	VCBO	–80	V
Collector–Emitter Voltage	VCEO	–65	V
Emitter–Base Voltage	VEBO	–5	V
Collector Current (DC)	IC	–100	mA
Peak Collector Current (Pulse)	ICP	–200	mA
Peak Base Current (Pulse)	IBP	–200	mA
Junction Temperature	TJ	150	°C
Storage Temperature Range	TSTG	–65 to +150	°C

Electrical Characteristics

Parameter	Symbol	Conditions	Min	Typ	Max	Unit
DC Current Gain	hFE	IC = −2 mA, VCE = −5 V	110	—	800*	—
Collector–Emitter Saturation Voltage	VCE(sat)	IC = −10 mA, IB = −0.5 mA	—	−0.09	−0.25	V
Base–Emitter Saturation Voltage	VBE(sat)	IC = −10 mA, IB = −0.5 mA	—	−0.55	−0.70	V
Collector Cutoff Current	ICBO	VCB = −30 V	—	—	−15	nA
Emitter Cutoff Current	IEBO	VEB = −4 V	—	—	−100	nA
Base–Emitter On Voltage	VBE(on)	IC = −2 mA, VCE = −5 V	−0.55	−0.65	−0.70	V
Transition Frequency	fT	IC = −10 mA, VCE = −5 V	—	150	—	MHz
Collector Output Capacitance	Cob	VCB = −10 V, f = 1 MHz	—	6	—	pF

BC556 Transistor Features

-PNP epitaxial silicon BJT for general-purpose use

-High collector–emitter voltage rating (–65 V

-Wide DC current gain range (110–800)

-Low noise performance ideal for audio circuits

-Low saturation voltage for efficient switching

-High transition frequency (150 MHz)

-Compact TO-92 through-hole package

BC556 Transistor Advantages

-Provides stable and reliable small-signal amplification

-Excellent performance in low-noise audio stages

-Versatile and can drive low-current loads easily

-Good thermal stability up to 150°C junction temperature

-Inexpensive and widely accessible for repairs or new designs

-Easily replaceable with several compatible PNP transistor models

BC556 Transistor Working in Circuit

The BC556 transistor in this circuit works as the upper PNP device in a push-pull amplifier stage, paired with an NPN BC546 transistor at the lower side. When an input signal is applied, each transistor responds to opposite signal polarities. As the input voltage goes low, the BC556 turns on and allows current to flow from the supply (VCC) toward the output, creating the upper half of the waveform. When the input signal goes high, the BC546 conducts and pulls the output node toward ground, forming the lower half of the waveform.

The shared resistor between the two transistors helps stabilize the operating point and ensures smooth signal transition between Q1 and Q2. In the second version of the circuit, the added resistors on the input side improve isolation, reduce loading, and help maintain better linearity. The BC556 enables clean amplification of the input by handling the positive portion of the signal in a complementary pair.

BC556 Transistor Applications

-Low-noise audio preamplifiers

-Small-signal audio amplification stages

-Signal processing and conditioning circuits

-General-purpose PNP switching applications

-Driver stages for low-current loads (LEDs, small relays, sensors)

-Push-pull amplifier stages when paired with NPN transistors (e.g., BC546/BC547)

-Voltage level shifting circuits

-Analog and linear amplifier stages

-Darlington PNP configurations

-Complementary transistor pairs in differential input circuits

-Low-power inverter and logic switching circuits

-Active filter and tone control circuits

-Low-frequency oscillator circuits

-Current mirror and constant-current source designs

-Battery-powered circuits requiring low saturation voltage

-Transistorized protection and cut-off circuits