Transistor Lead Identification

Transistor Lead Identification

PCBWay

There are three leads in a transistor ; collector, emitter and base .

DRex Electronics

When a transistor is to be connected in a circuit, it is necessary to know which terminal is which . The identification of the leads of transistor varies with manufacturer.

However, there are three systems in general use as shown in fig.1 .

transistor lead identification

Fig.1

(i) When the leads of a transistor are in the same plane and unevenly spaced as shown in fig.1 (i) , they are identified by the positions and spacings of leads .

  • The central lead is the base lead .
  • The collector lead is identified by the larger spacing existing between it and the base lead .
  • The remaining lead is the emitter .

trans1

(ii) When the leads of a transistor are in the same plane but evenly spaced as shown in fig.1 (ii) ;

  • The central lead is the base lead .
  • The lead identified by dot is the collector lead .
  • The remaining lead is the emitter .

trans2

(iii) When the leads of a transistor are spaced around the circumference of a circle as shown in fig.1 (iii) ;

  • The three leads are generally in E-B-C order clockwise from a gap .