The BC557 vs BC558 transistors are the best general-purpose components of the electronic circuits, both of them are PNP BJT transistors and they are alternate to each other.

In the post we try to compare BC557 vs BC558 differences such as voltage and current ratings, features, working theory, and applications, this BC557 vs BC558 comparison may surely useful for the circuit designers and students who curious about electronic components.


Pinout details of BC557 PNP

  1. Collector
  2. Base
  3. Emitter 
Pinout details of BC557 PNP
Pinout details of BC557 PNP

Pinout details of BC558 PNP

  1. Collector
  2. Base
  3. Emitter
Pinout details of BC558 PNP
Pinout details of BC558 PNP


The pinout details of BC557 vs BC558 are the same both of the transistors are PNP type, the current flow path is different from NPN, which is at PNP current flows into the transistor.

This is the reason why, the arrow at the emitter terminal indicates the current flow into the transistor, the whole working operation of PNP is opposite to NPN transistors. 

The material used to make this semiconductor transistor is silicon, which may be indicated with the letter B.

power rating of BC557

Voltage specifications

  • Emitter-base voltage(VEB) = 6v
  • Collector-emitter voltage (VCE) = 45v
  • Collector-base(VCB) = 50v

Current specifications

  • Collector current (IC) = 100mA
  • Peak collector current(IC) = 200mA
  • DC current gain = 300max
  • Base current (IB) = 5mA
  • Maximum collector dissipation = 500miliwatt
  • Minimum-Maximum DC current gain = 125 – 800
  • Transition frequency = 100mHZ
  • Maximum storage &operating temperature = -65 to 150˚C

power rating of BC558

Voltage specifications

  • Emitter-base voltage(VEB) = 5v
  • Collector-emitter voltage (VCE) = 30v
  • Collector-base(VCB) = 30v

Current specifications

  • Collector current (IC) = 100mA
  • Peak collector current(IC) = 200mA
  • DC current gain = 800max
  • Base current (IB) = 200mA peak
  • Maximum collector dissipation = 500miliwatt
  • Minimum-Maximum DC current gain = 100 – 800
  • Transition frequency = 100mHZ
  • Maximum storage &operating temperature = -65 to 150˚C


Working principle of BC557 vs BC558

The base terminal is the triggering point of the transistors BC557 and BC558, a small change in current at the base side will induce a large current change across other terminals.

The only difference at PNP transistor from NPN transistor is base terminal may be negative at PNP transistor, this is due to negative portion is been sandwiched between two positive portion. 

The power supply connections of the PNP transistor are opposite to the NPN transistor.


Working features 

The emitter-base voltage is 5v at BC558, due to this reason it can have the ability to work at the output of microcontrollers, and BC557 has 6v at the emitter-base junction.

Both BC557 vs BC558 prefer 100ma at load, more than this limit will damage the component.

And make sure that BC557 operates under 45V, DC, and on BC558 this limit is 30v.

Make sure to connect a suitable base resistor for both BC557 vs BC558.

The collector dissipation and DC gain values will help the device to works in amplification systems, for both BC557 vs BC558 had the same values.

At switching applications, BC557 and BC558 transistors can handle loads under 100 ma.

DC gain of both BC557 and BC558 is between 100 to 800, this will make them ideal transistors to use at small-scale amplifiers.


NPN complementary for BC557 and BC558

Both have the same complementary NPN transistors, BC547 and BC548 are the complementary transistors used at amplifiers.


Equivalent transistors

The equivalent or alternative transistor of both may have a different option, but first, we can say BC557 and BC558 are alternatives to each other.

For BC557, we have many options 2N3906, BC556, TIP42 and TIP127

For BC558, we have BC559 and TIP41


Advantage of BC557 and BC558

  • Compact in size
  • Cheap 
  • Long life span
  • Simpler circuit design 
  • Speedy action at the circuit
  • Required lower power supply
  • Low noise operation
  • Less output impedance 
  • Very current gain
  • Few component requirements 
  • Sensitive to current


  • Switching is low 
  • Limited bandwidth 
  • Phase-shifting problems at certain frequencies 
  • High power dissipation 
  • Over leakage current is high 
  • Not suitable for high-frequency signals
  • Temperature-sensitive 
  • Not suitable for higher power circuits


Applications of BC557 and BC558 

  • Amplifier circuits 
  • Small radio circuits
  • Switching circuits
  • Touch switch circuits
  • Electronic buzzers
  • Pre-amp audio circuits
  • Microcontroller power supply
  • It can be used for any type of general-purpose application.
  • Relay driving circuits
  • LED driving circuits
  • IC driving circuits 
  • Impedance buffer networks
  • Motor driving circuits
  • H-bridge circuits
  • Complementary transistor amplifier circuits 
  • Oscillator circuits
  • Comparator circuits 
  • Multi-vibrator circuits 



In this post we try to compare BC557 vs BC558 transistors, we know they are known as the general-purpose transistor type, due to this reason both of them have the enormous possibility of applications in our daily life.

The BC557 and BC558 are almost identical type PNP transistors, in some circuits, BC557 and BC558 will be replaced with each other.

We know the importance of DC gain on the amplifier circuit and other circuits, other than this, both BC557 and BC558 have produced almost identical but different DC gains.

The BC557A, BC557B, and BC557C components will produce a different range of DC gain. 

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