How To Calculate Base Resistor Of A Transistor In Electronic Circuits

If you are an electronic hobbyist you would very well know about transistors and how they work. Transistors basically have three leads viz. the base, the emitter and the collector. The emitter is the reference lead, or the common exit point for all potentials applied over the base and the collector. The base forms the trigger lead, while the collector becomes the load handling lead of the device. Transistors are primarily of two types, NPN and PNP, both behave similarly but with opposite polarities.
Using a transistor in electronic circuits is quite easy. If it’s a NPN transistor, connect the

emitter to negative of the supply line, connect the load which needs to be switched in between the positive supply line and the collector of the transistor. Now connect the base to the trigger voltage via a resistor to the trigger source, which may be from an IC output or other similar source.

A small voltage and current applied across base/emitter of the transistor will allow a relatively higher voltage and current to flow across collector/emitter. This voltage may be anywhere near or above 0.7 volts, which shows how minute can be the voltage for triggering a transistor. However this may not be true for the current parameter. The

required driving current over the base of a transistor will depend on the level of current that may be needed for switching the load comfortably or fully. This may be determined by using suitable formulas.

Therefore if the current required for operating the load at the collector of the transistor is known, the base current drive may be easily determined.

A new hobbyist may feel confused regarding the current which may be required for switching a particular load at the specified current. This may be easily found and confirmed either by measuring the resistance of the load or by practically connecting the load and an ammeter in series across the rated supply voltage.

Using an ammeter will provide you with a direct reading of the consumed current or the optimal current requirement of the load. If you want to identify this through the resistance of the load then you may to use the formula presented HERE.

The above link provides a comprehensive explanation regarding how to calculate the base resistor transistors while using in electronic circuits.

Article Written By Swagatam

Swagatam is a blogger at

Last updated on 25-07-2016 165 0

Please login to comment on this post.
There are no comments yet.
How To Make An Electronic Spy Bug Circuit Using Ic 741
How To Make A Balanced Microphone Preamplifier Circuit