BC109 Transistor Pinout, Equivalent, Uses, Features, Specs, and More

BC109 is a quite popular transistor and used in many circuits for many years. This post describes BC109 transistor pinout, equivalent, uses, features, specs, and other major information about this TO-18 metal case BJT transistor.


 BC109 Transistor Pinout, Equivalent, Uses, Features, Specs



Features / Technical Specifications:

  • Package Type: TO-18
  • Transistor Type: NPN
  • Max Collector Current(IC): 100mA
  • Max Collector-Emitter Voltage (VCE): 20V
  • Max Collector-Base Voltage (VCB): 30V
  • Max Emitter-Base Voltage (VBE): 5V
  • Max Collector Dissipation (Pc): 300 Milliwatt
  • Max Transition Frequency (fT): 100 MHz
  • Minimum & Maximum DC Current Gain (hFE): 200 to 800
  • Max Storage & Operating temperature Should be: -65 to 150 Centigrade


BC109 Transistor Explained / Description:

BC109 is a popular NPN transistor available in TO-18 metal package. It is a general-purpose transistor used in commercial and educational circuits. It is the transistor of the BC10x series; there are also other transistors in this series which are BC107 and BC108.

The transistor is designed for general switching and amplification purposes, the maximum collector current is 100mA, however, you will also see some differences in the collector current of the transistor with different manufacturers, some manufacturers have this available in 50mA collector current and some have it available in 100mA, so it is better to first confirm the transistor’s collector current from the supplier you are buying from.

The maximum collector to emitter voltage of the transistor is 20V which means that the transistor can drive maximum load voltage of 20V. Moreover, the maximum collector dissipation is 300mW and the DC current gain value is from 200 to 800, it also has a good noise figure of 4dB.

The transistor is available in three different hFE values which are BC109 hFE value is 200 to 800, BC109B hFE value is 200-450 and BC109C hFE value is 420 to 800.


PNP Complementary:

PNP Complementary of BC109 is BC177


Replacement and Equivalent:

The exact match transistor for BC109 is BC108. BC107 will also work but the only difference is its maximum DC current gain is 450 but in most cases, it will not make a big difference. Other nearest possible substitutes are A158C, BCY65X. If you can’t find these equivalents then you can also try the TO-92 Plastic package equivalents which are BC546, BC547, BC548, BC549, BC560.


Where We Can Use It & How to Use:

BC109 is a general-purpose transistor therefore it can be used in any general-purpose applications which fall under its specifications. It can be used to drive loads under 100mA. The low noise figure of 4dB makes it ideal to use for audio amplification, preamplification and any electronic signal amplification. The 100MHz  transition frequency also makes it ideal to use in RF circuits under 100MHz.



Audio amplifier Circuits

Any Signal Amplification

Audio Preamplifier

Darlington pair

RF circuits

Switching loads under 100mA


Safe Operating Guidelines / Absolute Maximum Ratings:

For safe operation, it is recommended to not use the transistor on its absolute maximum ratings and always stay 20% below. The maximum collector current of the transistor is 100mA therefore do not drive load of more than 80mA. The maximum collector-emitter voltage is 20V therefore do not drive load of more than 16V. The collector of the transistor is connected with its case, therefore, it is must to isolate the transistor from the circuit connections and always store and operate this transistor above -65 °C and below 150°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 *