BJT practice problems
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An ideal, uniformly doped silicon npn transistor has the following doping and widths.
|doping||NDE = 4.0e+17 cm-3||NAB = 2.0e+16 cm-3||NDC = 4.0e+15 cm-3|
|widths||WE = 4 μm||WB = 2 μm||WC = 3 μm|
The BJT area is 300 μm x 300 μm.
Calculate βF and IS for the BJT.
If the BJT is biased in forward active operation, with VBE = 0.65 V, calculate the base, collector, and emitter currents, assuming room temperature operation.
Note: For silicon,
- the intrinsic carrier concentration is ni = 6.0e+9 cm-3
- the electron diffusion coefficient is 35 cm2/s, and
- the hole diffusion coefficient is 10 cm2/s.
- βF = 140,
- IS = 4.54e-14 A,
- IC = 0.00396 A,
- IB = 2.83e-5 A, and
- IE = 0.00396 A.