Chapter Questions
Calculate the input and output power for the circuit of Fig. $35 .$ The input signal results in a base current of $5 \mathrm{~mA} \mathrm{rms}$.
Calculate the input power dissipated by the circuit of Fig. 35 if $R_{B}$ is changed to $1.5 \mathrm{k} \Omega$.
What maximum output power can be delivered by the circuit of Fig. 35 if $R_{B}$ is changed to $1.5$ $\mathrm{k} \Omega ?$
If the circuit of Fig. 35 is biased at its center voltage and center collector operating point, what is the input power for a maximum output power of $1.5 \mathrm{~W}$ ?
A class A transformer-coupled amplifier uses a $25: 1$ transformer to drive a $4-\Omega$ load. Calculate the effective ac load (seen by the transistor connected to the larger turns side of the transformer).
What turns ratio transformer is needed to couple to an $8-\Omega$ load so that it appears as an $8-\mathrm{k} \Omega$ effective load?
Calculate the transformer turns ratio required to connect four parallel $16-\Omega$ speakers so that they appear as an $8-\mathrm{k} \Omega$ effective load.
A transformer-coupled class A amplifier drives a $16-\Omega$ speaker through a $3.87: 1$ transformer. Using a power supply of $V_{C C}=36 \mathrm{~V}$, the circuit delivers $2 \mathrm{~W}$ to the load. Calculate:a. $P($ ac $)$ across transformer primary.b. $V_{L}(\mathrm{ac})$.c. $V(\mathrm{ac})$ at transformer primary.d. The rms values of load and primary current.
Calculate the efficiency of the circuit of Problem 8 if the bias current is $I_{C o}=150 \mathrm{~mA}$.
Draw the circuit diagram of a class A transformer-coupled amplifier using an $n p n$ transistor.
Draw the circuit diagram of a class B npn push-pull power amplifier using transformercoupled input.
For a class B amplifier providing a 22-V peak signal to an $8-\Omega$ load and a power supply of $V_{C C}=25 \mathrm{~V}$, determine:a. Input power.b. Output power.c. Circuit efficiency.
For a class B amplifier with $V_{C C}=25 \mathrm{~V}$ driving an $8-\Omega$ load, determine:a. Maximum input power.b. Maximum output power.c. Maximum circuit efficiency.
Calculate the efficiency of a class $\mathrm{B}$ amplifier for a supply voltage of $V_{C C}=22 \mathrm{~V}$ driving a 4- $\Omega$ load with peak output voltages of:a. $V_{L}(\mathrm{p})=20 \mathrm{~V}$.b. $V_{L}(\mathrm{p})=4 \mathrm{~V}$
Sketch the circuit diagram of a quasi-complementary amplifier, showing voltage waveforms in the circuit.
For the class B power amplifier of Fig. 36, calculate:a. Maximum $P_{o}(\mathrm{ac})$.b. Maximum $P_{i}(\mathrm{dc})$.c. Maximum \%\eta.d. Maximum power dissipated by both transistors.
If the input voltage to the power amplifier of Fig. 36 is $8-\mathrm{V} \mathrm{rms}$, calculate:a. $P_{i}(\mathrm{dc})$.b. $P_{o}(\mathrm{ac})$.
For the power amplifier of Fig. 37 , calculate:a. $P_{o}(\mathrm{ac})$.b. $P_{i}(\mathrm{dc})$.c. $\% \eta$.d. Power dissipated by both output transistors.
Calculate the harmonic distortion components for an output signal having fundamental amplitude of $2.1 \mathrm{~V}$, second harmonic amplitude of $0.3 \mathrm{~V}$, third harmonic component of $0.1 \mathrm{~V}$, and fourth harmonic component of $0.05 \mathrm{~V}$.
Calculate the total harmonic distortion for the amplitude components of Problem $19 .$
Calculate the second harmonic distortion for an output waveform having measured values of $V_{C E_{\min }}=2.4 \mathrm{~V}, V_{C E_{0}}=10 \mathrm{~V}$, and $V_{C E_{\max }}=20 \mathrm{~V}$
For distortion readings of $D_{2}=0.15, D_{3}=0.01$, and $D_{4}=0.05$, with $I_{1}=3.3 \mathrm{~A}$ and $R_{C}=4 \Omega$, calculate the total harmonic distortion fundamental power component and total power.
Determine the maximum dissipation allowed for a $100-\mathrm{W}$ silicon transistor (rated at $25^{\circ} \mathrm{C}$ ) for a derating factor of $0.6 \mathrm{~W} /{ }^{\circ} \mathrm{C}$ at a case temperature of $150^{\circ} \mathrm{C}$.
A $160-\mathrm{W}$ silicon power transistor operated with a heat sink $\left(\theta_{S A}=1.5^{\circ} \mathrm{C} / \mathrm{W}\right)$ has $\theta_{J C}=0.5^{\circ} \mathrm{C} / \mathrm{W}$ and a mounting insulation of $\theta_{C S}=0.8^{\circ} \mathrm{C} / \mathrm{W}$. What maximum power can be handled by the transistor at an ambient temperature of $80^{\circ} \mathrm{C}$ ? (The junction temperature should not exceed $200^{\circ} \mathrm{C}$.)
What maximum power can a silicon transistor $\left(T_{J_{\max }}=200^{\circ} \mathrm{C}\right)$ dissipate into free air at an ambient temperature of $80^{\circ} \mathrm{C}$ ?
Use Design Center to draw the schematic of Fig. 35 with $V_{i}=9.1 \mathrm{mV}$.
Use Design Center to draw the schematic of Fig. 36 with $V_{i}=25 \mathrm{~V}(\mathrm{p})$. Determine the circuit efficiency.
Use Multisim to draw the schematic of an op-amp class B amplifier as in Fig. 33. Use $R_{1}=10 \mathrm{k} \Omega, R_{F}=50 \mathrm{k} \Omega$, and $V_{i}=2.5 \mathrm{~V}(\mathrm{p}) .$ Determine the circuit efficiency.