3.2: NPN Transistor Operation

3.2 NPN Transistor Operation

For proper operation, the NPN and PNP transistors must be biased as shown in Figure 3.5.

Figure 3.5: Biased NPN and PNP Transistors for proper operation

The bias voltage sources are V _BB for the base voltage and V _CC for the collector voltage. Typical values for V _BB are about 1 V or less, and for V _CC about 10 V to 12 V. The difference in these bias voltages is necessary to cause current flow from the collector to the emitter in an NPN transistor and from the emitter to collector in a PNP transistor.

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