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Physics 2420 In-Class Problems: Transistors

  1. For the silicon (VBE = 0.7 V) transistor shown in the diagram below determine whether it is in saturation if
    (a) βDC = 50, VBB = 6.5 V, RB = 2500 Ω, RC = 500 Ω, VCC = 6.0 V, and VCE(sat) = 0.0V;
    (b) βDC = 75, VBB = 4.0 V, RB = 10 kΩ, RC = 100 Ω, VCC = 4.0 V, and VCE(sat) = 0.3V;
    (c) βDC = 180, VBB = 3.0 V, RB = 16 kΩ, RC = 400 Ω, VCC = 12.0, and VCE(sat) = 0.5V;
    (d) βDC = 125, VBB = 3.9 V, RB = 40 kΩ, RC = 2.0 kΩ, VCC = 9.5, and VCE(sat) = 0.4V.

  2. Under the following set of conditions determine IC(sat). What is the minimum of IB that produces saturation. What minimum value of VBB produces saturation. Refer to the diagram above. Take VBE = 0.7 V.
    (a) βDC = 50 , RB = 2500 Ω, RC = 500 Ω, VCC = 6.0 V, and VCE(sat) = 0.0 V;
    (b) βDC = 75, RB = 10000 Ω, RC = 100 Ω, VCC = 4.0 V, and VCE(sat) = 0.3 V;
    (c) βDC = 180, RB = 16000 Ω, RC = 400 Ω, VCC = 12.0 V, and VCE(sat) = 0.5 V;
    (d) βDC = 125 , RB = 40 kΩ, RC = 2.0 kΩ, VCC = 9.5 V, and VCE(sat) = 0.4 V.

  3. For the following sets of conditions determine the Q-point. Determine the maximum peak value of the base current Ib . If the maximum value is exceeded, will the signal be driven into cutoff, or saturation, or both? Take VBE = 0.7 V and VCE(sat) = 0.0 V.
    (a) βDC = 50, VBB = 1.0 V, RB = 2500 Ω, RC = 500 Ω, VCC = 6.0 V;
    (b) βDC = 25, VBB = 1.0 V, RB = 2500 Ω, RC = 500 Ω, VCC = 6.0 V;
    (c) βDC = 75, VBB = 1.0 V, RB = 2500 Ω, RC = 500 Ω, VCC = 6.0 V.

  4. The diagram below shows a base-biased transistor. For the following sets of conditions determine the Q-point. Determine the maximum peak value of the base current. If the maximum value is exceeded, will the signal be driven into cutoff, or saturation, or both? Take VBE = 0.7 V and VCE(sat) = 0.0 V.
    (a) βDC = 200, RB = 75 kΩ, RC = 200 Ω, and VCC = 15.0 V;
    (b) βDC = 100, RB = 75 kΩ, RC = 200 Ω, and VCC = 15.0 V;
    (c) βDC = 300, RB = 75 kΩ, RC = 200 Ω, and VCC = 15.0 V.

  5. The diagram below shows an npn emitter-biased transistor. For the following sets of conditions determine the Q-point. Determine the maximum peak value of the base current. If the maximum value is exceeded, will the signal be driven into cutoff, or saturation, or both? Take VCE(sat) = 0.0 V.
    (a) βDC = 150, RB = 10 kΩ, RC = 1.0 kΩ, RE = 3.0 kΩ, VCC = 9.0 V, VEE = 9.0 V, and VBE = 0.7 V;
    (b) βDC = 300, RB = 10 kΩ, RC = 1.0 kΩ, RE = 3.0 kΩ, VCC = 9.0 V, VEE = 9.0 V, and VBE = 0.6 V;
    (c) βDC = 150, RB = 10 kΩ, RC = 1.0 kΩ, RE = 1.5 kΩ, VCC = 9.0 V, VEE = 9.0 V, and VBE = 0.7 V;
    (d) βDC = 150, RB = 10 kΩ, RC = 1.0 kΩ, RE = 4.5 kΩ, VCC = 9.0 V, VEE = 9.0 V, and VBE = 0.7 V.

  6. For the npn emitter-biased transistor shown above, what would be the minimum value of RE that keeps the transistor from going into saturation?
    (a) βDC = 150, RB = 10 kΩ, RC = 1.0 kΩ, VCC = 9.0 V, VEE = 9.0 V, VBE = 0.7 V, and VCE(sat) = 0.5 V,
    (b) βDC = 300, RB = 10 kΩ, RC = 1.0 kΩ, VCC = 9.0 V, VEE = 9.0 V, VBE = 0.6 V, and VCE(sat) = 0.4 V,
    (c) βDC = 220, RB = 1200 Ω, RC = 700 Ω, VCC = 6.0 V, VEE = 6.0 V, VBE = 0.7 V, and VCE(sat) = 0.7 V.

  7. The diagram below shows a transistor with a voltage-divider bias. For the following sets of conditions determine the Q-point. Determine the maximum peak value of the base current. If the maximum value is exceeded, will the signal be driven into cutoff, or saturation, or both? Take VCE(sat) = 0.0 Volts.
    (a) βDC = 100, VCC = 8.0 V, VBE = 0.7 V, RC = 1.4 kΩ, RE = 600 Ω, R1 = 25 kΩ, and R2 = 12 kΩ;
    (b) βDC = 200, VCC = 8.0 V, VBE = 0.6 V, RC = 1.4 kΩ, RE = 600 Ω, R1 = 25 kΩ, and R2 = 12 kΩ;
    (b) βDC = 300, VCC = 8.0 V, VBE = 0.6 V, RC = 1.4 kΩ, RE = 600 Ω, R1 = 25 kΩ, and R2 = 12 kΩ.

  8. The diagram above shows a voltage-divider biased transistor. What is the minimum value of R2 which causes saturation?
    (a) βDC = 100, VCC = 8.0 V, VBE = 0.7 V, RC = 1.4 kΩ, RE = 6.0 kΩ, R1 = 25 kΩ, and VCE(sat) = 0.0 V;
    (b) βDC = 200, VCC = 8.0 V, VBE = 0.7 V, RC = 1.4 kΩ, RE = 6.0 kΩ, R1 = 25 kΩ, and VCE(sat) = 0.0 V;
    (c) βDC = 300, VCC = 8.0 V, VBE = 0.7 V, RC = 1.4 kΩ, RE = 6.0 kΩ, R1 = 25 kΩ, and VCE(sat) = 0.5 V;

  9. Determine re, Rin(base) , Rin, Av, A'v for the following amplifier if
    (a) Rs = 850 Ω, β = 92, RC = 140 kΩ, RE = 60 kΩ, R1 = 25 kΩ, and R2 = 12 kΩ;
    (b) Rs = 175 Ω, β = 180, RC = 25 kΩ, RE = 5.0 kΩ, R1 = 2.5 kΩ, and R2 = 2.8 kΩ.

  10. Determine Av, A'v, for the amplifier in the problem above if RE is bypassed by a capacitor.

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