4. For maximum transfer of power between stages, the output impedance of the
first stage must be matched to the input impedance of the second.
The coupling
method that best can match the high impedance of a power amplifier to the low
impedance of a loudspeaker voice coil is
a. direct coupling.
c. resistance coupling.
b. impedance coupling.
fidelity is to be expected.
This type of distortion is produced in an audio
amplifier when
a. negative feedback is permitted to occur.
b. the amplification of each input frequency is not uniform.
c. the amplitudes of different signal frequencies vary in the output.
d. certain additional frequencies, not present in the original input signal,
are reproduced.
6. The most important consideration in voice communication is that the receiver
provides
a. high fidelity.
b. good intelligibility.
c. high harmonic content.
d. low-frequency distortion over the entire AF range.
7. The reason that harmonic distortion more seriously affects the quality of an
audio signal than does frequency distortion is that harmonic distortion
a. attenuates frequencies on either side of the 150-to 3,500-Hz band.
b. minimizes the sum and difference frequencies that improve speech quality.
c. introduces new frequencies that were not originally present in the signal.
d. cancels out the intermodulation products that produce intelligible speech.
8. Degeneration, or negative feedback, improves the operating characteristics of
an audio amplifier by reducing the frequency and nonlinear distortion, and by
improving the amplifier's stability.
The function of a negative feedback circuit
is to feed back a voltage that
a. equals the output signal voltage.
b. opposes the applied input signal voltage.
322 L4
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