NPN Biasing:

The common method of biasing an npn transistor is to have the emitter more negative than the collector. In most situations, the emitter is at or near zero potential whereas the collector is connected to a source of positive dc voltage. This is exposed by the connection of the battery in figure shown below. Typical voltages variety from 3 V to around 50 V.

The base is labeled "control" since the flow of current via the transistor depends on the base bias voltage, represented by EB or VB, relative to the emitter-collector bias voltage, represented by EC or VC.

Figure: Typical biasing of an npn transistor