BC178 Transistor Pinout, Equivalent, Uses, Features, Where and How to Use and More

Today we will understand BC178 transistor details such as its pinout, equivalent, uses, features, where and how to use and the electrical characteristics.


BC178 Transistor Pinout, Equivalent, Uses, Features, Where and How to Use and More


Absolute Maximum Ratings:

  • Package Type: TO-18
  • Transistor Type:  PNP
  • Max Collector Current(IC): -100A
  • Max Collector-Emitter Voltage (VCEO): -25V
  • Max Emitter-Base Voltage (VEBO): -5V
  • Max Collector Power Dissipation (PC): 300 Miliwatt
  • Max Transition Frequency (fT): 200 MHz
  • Minimum & Maximum DC Current Gain (hFE): 125 to 500
  • Max Storage & Operating temperature Should Be: -65 to +175 Centigrade


PNP Complementary:

PNP Complementary of BC178 is BC108


Replacement and Equivalent:

2SA1218, BC291, BC266, BC292, BCY71, BC477, BCY77, BC177A, BC177B. Plastic case replacement can be BC560, BC556, BC558, BC557, BC559.


BC178 Transistor Explained / Description:

BC178 is a metal case transistor available in TO-18 metal case. It is a PNP transistor designed to be used in general purpose switching and amplification applications. Looking at the pin layout of the transistor the pin1 is Emitter, pin2 is Base and pin3 is Collector.

BC178 is a transistor of BC17x series which also contains other two transistors which are BC177 and BC179. There is also the NPN complementary series of these transistors which contains BC107, BC108, and BC109. All these transistors are widely used in different types of commercial electronic applications.

Looking at the absolute maximum ratings of the transistor, max collector-emitter voltage is -25V, the max collector current is -100mA, max emitter-base voltage is -5V, max collector dissipation is 300mW and max storage and operating temperature of the transistor is -65 °C to +175 °C. These are the maximum limits of the transistor so it is suggested to not use the transistor to its absolute maximum ratings and always stay at leat 20% below from these ratings for good performance.

As regarding to the electrical characteristics some main characteristics are as follows: it has a DC current gain of 120 to 500, the transition frequency is 200MHz and maximum noise figure is 10dB.

The transistor comes in two different gain values which can be determined with the help of the alphabet written after its part number, if that alphabet is “A” then its gain value will be from 125 to 260 and if the alphabet is “B” then its gain value will be 240 to 500.


Where We Can Use it & How to Use:

BC178 can be used in wide variety of general purpose switching and amplification applications. It has a collector current of 100mA which means it can drive load of up to 100mA and suitable to drive loads such as LEDs, low current motors, ICs, power transistors etc. Moreover, it is also a good candidate as a small signal amplifier and due to its good DC current gain and low noise features it can also be used in audio preamplifiers and also to amplify different types of small signals in electronics. Additionally, the transition frequency of 200MHz also makes it ideal to be used in RF circuits.



Signal Amplification

Audio Amp Stages

Audio amplifier circuits

Output of Microcontrollers for Driving Different Loads

Drive Loads Under 800mA


Safe Operating Guidelines:

Here are some guidelines to use the transistor safely.

  • As already mentioned above do not use the transistor to its absolute maximum ratings and stay at least 20% below.
  • Therefore according to the above guideline, the maximum collector to emitter voltage of the transistor is -25V but we will not drive load of more than -20V.
  • The max collector current is -100mA so we will not drive load of more than -80mA.
  • Moreover, the minimum and maximum operating and storage temperature should be between -65 °C to +175 °C.



To download the datasheet just copy and paste the below link in your browser.


You may also like...

Leave a Reply

Your email address will not be published. Required fields are marked *