engleski

The Effect of Bipolar Transistor Design on the Cutoff Frequency

The influence of the concentration of extrinsic, intrinsic base and collector impurities on the npn bipolar transistor cutoff frequency (fT) are investigated in this work. The four different combination of impurity concentrations in the mentioned regions were analyzed, first by TMA MEDICI device simulator, and then by analytical calculation. It is shown that the influence of extrinsic part of a base is very small. The base width is very short, and all time constants are of the same order of magnitude. Because of small geometrical dimensions the influence of Kirk effect on the base width is taken into account. It is shown that this effect play important role in determination of cutoff frequency.

cuttof frequency; extrinsic base; base width; time constant; Kirk effect; MEDICI

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