BC548 transistor Pinout, Specifications, Datasheet and Applications

Last updated on March 27th, 2024 at 12:42 pm

BC458 is a general-purpose NPN transistor used in many electronics projects and devices. BC548 transistor is used for amplifying and switching purposes in electrical circuits. Like every other NPN transistor, it consists of three pins: the collector, base, and emitter.

BC548 transistor pinout

It is a low-cost and widely used transistor. Some other widely used substitutes of BC458 are BC549, BC547, 2N3904, BC108, BC550, BC546, 2N2222,

Features / technical specifications

• Package Type: TO-92
• Transistor Type: NPN
• Max Collector Current (IC): 500mA
• Max Collector-Emitter Voltage (VCE): 30V
• DC Current Gain range (hFE): 110 – 800
• Max Collector-Base Voltage (VCB): 30V
• Max Emitter-Base Voltage (VEBO): 5V
• Low Noise: <10 dB
• Max. Collector Dissipation (Pc): 625 milliwatt
• Max Transition Frequency (fT): 150 MHz
• Max Storage & Operating temperature Should Be: -55 to +150oC

20 PCS OF BC548 in transistor kit

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Working states OR modes of operation of BC548

Like every other transistor BC548 transistor works in three regions:

• Cut off Region.
• Saturation Region.
• Active Region

(a) Cut-off region

In the cut-off region, the transistor works as an open circuit or open switch. The base, collector, and emitter currents are all zero in this region. In the cut-off region, both the collector and emitter junctions are reverse-biased. Hence in the cut-off region, the base, emitter, and collector current are zero. This gives

I_C=I_E=I_B=0

here I_C = collector current, I_E = emitter current, and I_B = base current.

(b) Saturation region

In the saturation region, the transistor works like a short circuit or closed switch. The collector and Emitter currents are maximum in this region. In the saturation region, both the collector and emitter junctions are forward-biased. In other words, the transistor operates as a short circuit or closed switch carrying maximum current which implies:

I_C=I_E

here I_C = collector current and I_E = emitter current.

(c) Active region

The active region lies between the cut-off and saturation regions. In the active region, the transistor emitter junction is forward-biased and the collector junction is reverse-biased. In the active region, the collector current is β times the base current, i.e.,

I_C=β I_B

here, I_C = collector current

Β = current amplification factor

I_B = base current

So the collector current increases in proportional to the base current.

BC548 transistor as a switch

The regions responsible for a transistor to work as a switch are the Saturation Region and the Cut-off Region. When we apply a high enough current at the base of the transistor, it makes a path for the collector current to go through the base toward the emitter.

To use the transistor as a switch, it must be driven into the saturation region with enough base current. A transistor operates as a closed switch under the saturation region.

As soon as a positive signal (in the form of voltage and current) is removed across the base of the transistor, the flow of electric current between the collector and emitter becomes zero. And the transistor behaves like an open switch under the cut-off region.

This simply implies if we apply signal (voltage/current) across the collector and emitter but not across the base, the transistor will not work. But a small signal across the base is enough to make it work.

BC548 transistor as an amplifier

A transistor acts as an amplifier by increasing the strength of a weak signal applied at its base. Transistors work as an amplifier in the active region or linear region. The figure given below shows how to use a transistor as an emitter amplifier.

**Image Source: instrumentationtools

In this region, with the increase in the base current, the collector current also increases proportionally according to the formula:

I_C=β I_B

Here, I_C = collector current

Β = current amplification factor

I_B = base current

Thus, a small input signal results in a large output, which implies that the transistor works as an amplifier.

Datasheet

BC547 comes in two packages: SMD and TO-92 package respectively.

Click this link to view the entire DATASHEET of BC548

You can find detailed information on BC548 in the datasheet given above. Specifications and characteristics like Absolute maximum ratings, Block diagrams, biasing methods, and package dimensions can be found in the datasheet.

Applications

• Amplification
• Switching
• Oscillators
• Signal Modulation
• Voltage Regulation
• Audio Amplification
• Darlington Pair Configuration
• Light Sensing
• Temperature Sensing
• Logic Gates

FAQs