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Transistor base Resistor Calculator

Calculator

Vbe

Vce

hFE

First you must check the datasheet of the transistor in question and identify the values Vbe, Vce, and hFE. These values are responsible for enabling transistor saturation. Here the example numbers shown are for the BJT BC548.

RL

Vcc

Vi

The load resistance RL is indicated in ohms, the supply voltage input is indicated as Vcc, and the input trigger voltage is indicated as Vi.

Rb:

Reader Interactions

Comments

  1. Ali Khorshidi says

    December 21, 2022

    please tell me how can i calculate voltage divider resistances for common emitter transistors in regulator or relay switching circuits .
    and if we have voltage divider is still a base resistor necessary ?

    Reply
    • Swagatam says

      December 21, 2022

      Please search online for “Voltage divider formula” you will get it quickly.
      No other resistor will be required when voltage divider is added to the base of the transistor.

      Reply
  2. Adriano Angeli says

    September 26, 2021

    I observe the characteristics of the BC548 transistor in the transistor comparison table published by the ECA
    The characteristics in your calculations do not match. If you are kind enough to tell me which book you are referring to. I thank

    Reply
    • Swagatam says

      September 27, 2021

      The above calculator is a standard transistor calculator software, so it cannot be wrong, but I have no idea why and how it may not be matching with your specified comparison table.

      Reply
  3. JOHN CROW says

    January 2, 2021

    Can you tell me the formula for this calculation?

    Reply
    • Swagatam says

      January 2, 2021

      R = (base input Voltage – 0.6) / Collector load current

      Reply
      • JOHN CROW says

        January 26, 2021

        Thank You

        Reply
  4. Alan Corey says

    August 21, 2020

    Glad to see somebody did this. I think it could be expanded to provide most or all of the numbers required for Dual Feedback Transistor Biasing if the right numbers are fed into it. Most of the numbers on https://www.electronics-tutorials.ws/amplifier/transistor-biasing.html for example could be worked out. I think, right now I want to build a preamp, not write a program.

    Reply
  5. Jeroen Vrij says

    March 17, 2019

    What means NAN

    Reply
    • Swagatam says

      March 17, 2019

      not a number

      https://en.wikipedia.org/wiki/NaN

      Reply
  6. yunishe anslemo says

    February 15, 2018

    Pls I want to begin with wireless circuits

    Reply
  7. Hamid Hussain says

    January 7, 2018

    Vce if bc548 is very low

    Reply
  8. Hamid Hussain says

    January 7, 2018

    If the transistor is bc547 what should be base resistor

    Reply
    • Swagatam says

      January 7, 2018

      Vce is the saturation voltage (minimum).

      for BC547 you have to only consider the hFe and the RL, rest all can be as it is

      Reply

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