hw_8_sol

# hw_8_sol - Homework 8 Solutions 9.3 Draw the energy band...

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Homework 8 Solutions 9.3. Draw the energy band diagram for a pnp transistor at equilibrium and under forward active bias. The drawing should reflect the relative dopings as well: p+ emitter n base p collector p+ collector equilibrium E ,E f C E V active mode bias F n F p I n I p -W W x E BM E ,E f C E V E ,E f V C E 9.5. Using the prototype model, (i.e. ignore the apparent band-gap narrowing and its effect on injection efficiency) find α and β for an npn BJT with Indicate clearly all your steps. Let V BE =0.8V V CB =2.0 V. The metallurgical widths are W EM = 0.2 μ m and W BM = 0.2 μ m. 19 3 17 3 17 3 10 , 2 10 , 10 . DE AB DC N cm N cm and N cm −− == × = We can find the minority carrier diffusion constants from Figure 3.11: D pE =3.8 cm 2 /s and D nB =15 cm 2 /s The built-in voltages for the two junctions are from Equation (5.13):

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() ( ) 19 17 22 10 3.1 10 2 10 ln 0.026 ln 1.00 1.08 10 VA B bi EB i NN kT VV q n ⎡⎤ ×× == ⎢⎥ ⎣⎦ × = (one-sided junction) and ( ) 17 17 10 10 2 10 ln 0.026ln 0.85 1.08 10 DC AB bi CB i kT q n × × = If the forward bias on the EB junction is 0.8V, then the junction voltage is V J(EB) =1.00-0.8=0.2V, and
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## This note was uploaded on 01/11/2012 for the course ECE 432 taught by Professor Lu during the Fall '08 term at Ohio State.

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hw_8_sol - Homework 8 Solutions 9.3 Draw the energy band...

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