UNBIASED TRANSISTOR
- An unbiased transistor means a transistor with no external voltage (biasing) is applied. Obviously, there will be no current flowing from any of the transistor leads.
- Since transistor is like two pn junction diodes connected back to back, there are depletion regions at both the junctions, emitter junction and collector junction, as shown in the Fig
- During diffusion process, depletion region penetrates more deeply into the lightly doped side in order to include an equal number of impurity atoms in the each side of the junction.
- As shown in the Fig. depletion region at emitter junction penetrates less i the heavily doped emitter and extends more in the base region.
- Similarly, depletion region at collector junction penetrates less in the heavily doped collector and extends more in the base region.
- As collector is slightly less doped than the emitter, the depletion layer Width at the collector junction is more than the depletion layer width at the emitter junction.
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