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Unformatted text preview: Ling: LL’u‘E ‘ * ECE 131A $0iid—State Materiais & Devices Final Examination] Spring 2011 1. The cut—in voltage V7 = 0.7V, the forward resistance rf = 0 and VT = 26mV for the diodes
D1 and D2 in the circuit given below. The source vs(t) = 6 + 0.23in(4t) V. 809 1600 D1 3) Determine the state of the diodes D1 and D2, and the Q—point := (V0Q , IOQ) for the circuit.
b) Obtain the equivalent small-signal (AC) model for the circuit.
c) Determine the the expression for the total voltage vo(t). (25%) 2. The parameters of the bipolar junction transistor (BJT) in the circuit given below are: B =
100, VT = 26mV, VBE(on) = 0.7V and VA = co. The resistor values are: Ri = R2 =100k£2 and RL = 10kg. R: -Vcc = —5v a) Design the circuit such that the Q-point := (ch, ICQ) = (3V, 0.25mA).
b) Determine the small-signal voltage gain Av deﬁned by v0 := Avvs for the circuit in part (a).
c) Determine for the circuit of part (a) the input resistance Ri deﬁned by vs := Riis. (25%) ECE 131A Solid-State Materials & Devices Final Examination I Spring 2011 3. In the circuit shown below the cut—in voltage V, = 0.5V and rf = O for the diodes D1 and D2.
a) Determine the transfer characteristic v0 versus vi and then given an appropriately labelled sketch for it for -2V 3 vi s 15V.
b) Give a sketch for i versus vi, ~2V s vi 5 15V. 10V (25%) 4. The transistor used in the circuit given in the ﬁgure below has turn-on voltage vBE(on) =
0.7V and B = 100. The resistor values are: R1 = 20kg, R2 =100kQ, RC = IkQ and RL = 5kg... VCC=5V vB =' -5v a) Determine the range of values for the input voltage Vin that would restrict the output voltage V0 to the range 1V s VO 3 4V.
b) Determine the DC load line equation and then, give a sketch for the DC load line and show on it the range of Q—point values corresponding to the result in part (a). (25%) ...
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