Base-Emitter Voltage

The entire normal range of silicon transistor operation involves a change in base-emitter voltage of only about two-tenths of a volt. This is because the base-emitter diode is forward biased. One of the constraints on transistor action is that this voltage remains at about 0.6 volts (often referred to as the diode drop). A small change in VBE can produce a large change in collector current and achieve current amplification.