Transistor Lead Identification

Transistor Lead Identification

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

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 .

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 .

(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 .

(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 .