How to Find Equivalent Transistors

Transistors are special types of electrical components that amplify current. All transistors have three main electrical leads: a base, a collector and an emitter. While their meanings are unimportant for their use, it is important to correctly determine which lead is which. When you connect a transistor into a circuit, it is essential to connect the three leads correctly, or else you risk immediate permanent damage to the transistor. There are two main transistor properties to match in order to find a suitable equivalent transistor to the one your plan requires: maximum collector current and current gain.

• 1

  Match the current gain from the original transistor to the equivalent transistor. Gain is the ratio of output current to input current or how much it amplifies. Typical gain values range from as low as 10 up to the 400s and even higher. It would be useless to replace a transistor with one whose gain value differs from its own.

• 2

  Ensure the maximum collector current on the equivalent transistor is at least as high as that of the original. Collector current is the magnitude of current the transistor is capable of outputting. The new transistor must be able to output at least as much current as the original.

• 3

  Carefully identify the base, collector and emitter leads on the new transistor. Be certain that you connect them to your circuit in the same manner your circuit demands of the original transistor, lest you quickly break your transistor.