Static Current Amplification:

The maximum available current amplification factor of a bipolar transistor is termed as the beta of the transistor. Depending on the manner in which a transistor is prepared, the beta can range from a factor of a few times up to hundreds of times. One technique of expressing the beta of a transistor is as the static forward current transfer ratio, represented by HFE. This is the ratio of the collector current to the base current as follows:

H_FE = I_C/I_B

For illustration, when a base current I_B of 1 mA generates a collector current I_C of 35 mA, then H_FE = 35/1 = 35. When I_B = 0.5 mA and I_C = 35 mA, then H_FE = 35/0.5 = 70.