What is audio amplifier?

What is audio amplifier?
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Answer :

The amplifier receives an input from signal source or from a transducer and gives out an amplified signal to the output device is called an audio amplifier. 
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Related questions

Which standard is utilized in intermodulation noise rates on PCM audio channels? A. CCIT Rec. G.151 B. CCIT Rec. G.172 C. CCIT Rec. G.190 D. CCIT Rec. G.190

Description : Which standard is utilized in intermodulation noise rates on PCM audio channels? A. CCIT Rec. G.151 B. CCIT Rec. G.172 C. CCIT Rec. G.190 D. CCIT Rec. G.190

Last Answer : B. CCIT Rec. G.172

A form of regenerative repeater for transmitting signals over a long cable received through a relay in a clearer form. A. Active generator B. Active repeater C. Interpolator D. Audio generator

Description : A form of regenerative repeater for transmitting signals over a long cable received through a relay in a clearer form. A. Active generator B. Active repeater C. Interpolator D. Audio generator

Last Answer : C. Interpolator

Where is the brightness control located in a TV? A. The audio section B. The video section C. The grid-cathode circuit D. The front panel

Description : Where is the brightness control located in a TV? A. The audio section B. The video section C. The grid-cathode circuit D. The front panel

Last Answer : A. The audio section

A test method of comparing two audio systems by switching inputs so that the same recording is heard in rapid succession over one given system and then the other. A. B test B. A test C. AB test D. C test

Description : A test method of comparing two audio systems by switching inputs so that the same recording is heard in rapid succession over one given system and then the other. A. B test B. A test C. AB test D. C test

Last Answer : C. AB test

What is the standard test tone used for audio measurements? A. 100 Hz B. 500 Hz C. 1000 Hz D. 2000 Hz

Description : What is the standard test tone used for audio measurements? A. 100 Hz B. 500 Hz C. 1000 Hz D. 2000 Hz

Last Answer : C. 1000 Hz

A 1 Mhz carrier is amplitude modulated by a pure 200-Hz audio test tone. Which of the following combinations of frequencies represent the total content of the AM signal? A. 1 MHz and 200 Hz B. 1 MHz and 1000.2 kHz C. 999.8 kHz, 1000 kHz, and 1000.2 kHz D. 999.8 kHz and 1000.2 kHz

Description : A 1 Mhz carrier is amplitude modulated by a pure 200-Hz audio test tone. Which of the following combinations of frequencies represent the total content of the AM signal? A. 1 MHz and 200 Hz B. 1 MHz and 1000.2 kHz C. 999.8 kHz, 1000 kHz, and 1000.2 kHz D. 999.8 kHz and 1000.2 kHz

Last Answer : C. 999.8 kHz, 1000 kHz, and 1000.2 kHz

What is meant by the term modulation index? A. The processor index. B. The ratio between the deviation of a frequency modulated signal and the modulating frequency. C. The FM signal-to-noise ratio. D. The ratio of the maximum carrier frequency deviation to the highest audio modulating frequency.

Description : What is meant by the term modulation index? A. The processor index. B. The ratio between the deviation of a frequency modulated signal and the modulating frequency. C. The FM signal-to-noise ratio. D. The ratio of the maximum carrier frequency deviation to the highest audio modulating frequency.

Last Answer : B. The ratio between the deviation of a frequency modulated signal and the modulating frequency.

What is meant by the term deviation ratio? A. The ratio of the audio modulating frequency to the center carrier frequency. B. The ratio of the maximum carrier frequency deviation to the highest audio modulating frequency. C. The ratio of the carrier center frequency to the audio modulating frequency. D. The ratio of the highest audio modulating frequency to the average audio modulating frequency.

Description : What is meant by the term deviation ratio? A. The ratio of the audio modulating frequency to the center carrier frequency. B. The ratio of the maximum carrier frequency deviation to the highest ... . D. The ratio of the highest audio modulating frequency to the average audio modulating frequency.

Last Answer : B. The ratio of the maximum carrier frequency deviation to the highest audio modulating frequency.

What is meant by the term deviation ratio? A. The ratio of the carrier center frequency to the audio modulating frequency B. The ratio of the highest audio modulating frequency to the average audio modulating frequency C. The ratio of the maximum carrier frequency deviation to the highest audio modulation frequency D. The ratio of the audio modulating frequency to the center carrier frequency

Description : What is meant by the term deviation ratio? A. The ratio of the carrier center frequency to the audio modulating frequency B. The ratio of the highest audio modulating frequency to the ... audio modulation frequency D. The ratio of the audio modulating frequency to the center carrier frequency

Last Answer : C. The ratio of the maximum carrier frequency deviation to the highest audio modulation frequency

________ is the method of encoding audio signals used in US standard 1544 kbit/s 24 channel PCM systems. A. Shannon’s law B. A-law C. Newton’s law D. Mu-law

Description : ________ is the method of encoding audio signals used in US standard 1544 kbit/s 24 channel PCM systems. A. Shannon’s law B. A-law C. Newton’s law D. Mu-law

Last Answer : D. Mu-law

How can receiver desensitizing be reduced? A. Increase the receiver bandwidth B. Ensure good RF shielding between the transmitter and receiver C. Increase the transmitter audio gain D. Decrease the receiver squelch, gain.

Description : How can receiver desensitizing be reduced? A. Increase the receiver bandwidth B. Ensure good RF shielding between the transmitter and receiver C. Increase the transmitter audio gain D. Decrease the receiver squelch, gain.

Last Answer : D. Decrease the receiver squelch, gain.

An instrument for recording waveforms of audio frequency. A. Oscilloscope B. Phonoscope C. Radioscope D. Audioscope

Description : An instrument for recording waveforms of audio frequency. A. Oscilloscope B. Phonoscope C. Radioscope D. Audioscope

Last Answer : B. Phonoscope

What is the effect in over modulated amplitude modulated radio broadcasting transmission? A. Interference to adjacent channel B. Higher fidelity C. Increase noise D. Higher audio signal

Description : What is the effect in over modulated amplitude modulated radio broadcasting transmission? A. Interference to adjacent channel B. Higher fidelity C. Increase noise D. Higher audio signal

Last Answer : A. Interference to adjacent channel

Atmospheric noise is less at severe frequencies above A. Audio level B. 30 MHz C. 10 GHz D. 1 GHz

Description : Atmospheric noise is less at severe frequencies above A. Audio level B. 30 MHz C. 10 GHz D. 1 GHz

Last Answer : B. 30 MHz

______ used to measure speech volume A. Volume meter B. Audio frequency meter C. Volume unit meter D. Speech meter

Description : ______ used to measure speech volume A. Volume meter B. Audio frequency meter C. Volume unit meter D. Speech meter

Last Answer : C. Volume unit meter

Which of the following is not a baseband signal modulation? A. RF carrier B. Video System C. Audio signal D. Binary coded pulses

Description : Which of the following is not a baseband signal modulation? A. RF carrier B. Video System C. Audio signal D. Binary coded pulses

Last Answer : A. RF carrier

The ratio of the level of the modulated output of a transmitter under conditions of standard test modulation to the level of the demodulated output with no modulation applied both measured with the same bandwidth. A. Reference audio output B. None of these C. Audio frequency response D. Residual noise level

Description : The ratio of the level of the modulated output of a transmitter under conditions of standard test modulation to the level of the demodulated output with no modulation applied both measured with the ... . Reference audio output B. None of these C. Audio frequency response D. Residual noise level

Last Answer : D. Residual noise level

What is the difference between phase and frequency modulation? A. Is purely theoretical because they are the same in practice B. Lies in poorer audio response of phase modulation C. Lies in the different definitions of the modulation index D. Is too great to make two systems compatible

Description : What is the difference between phase and frequency modulation? A. Is purely theoretical because they are the same in practice B. Lies in poorer audio response of phase modulation C. Lies in the different definitions of the modulation index D. Is too great to make two systems compatible

Last Answer : C. Lies in the different definitions of the modulation index

Three audio waves with 100,200 and 300 volts amplitude respectively, simultaneously modulate a 450 volts carrier. What is the total percent of modulation of the AM wave? A. 69 % B. 115.5 % C. 50% D. 83%

Description : Three audio waves with 100,200 and 300 volts amplitude respectively, simultaneously modulate a 450 volts carrier. What is the total percent of modulation of the AM wave? A. 69 % B. 115.5 % C. 50% D. 83%

Last Answer : D. 83%

ECE Board Exam March 1996 According to the Nyquist theorem, the sampling rate that can be used in a PCM system is ________ the highest audio frequency. A. once B. eight times C. twice D. thrice

Description : ECE Board Exam March 1996 According to the Nyquist theorem, the sampling rate that can be used in a PCM system is ________ the highest audio frequency. A. once B. eight times C. twice D. thrice

Last Answer : C. twice

Mention any two audio frequency oscillators .

Description : Mention any two audio frequency oscillators .

Last Answer : i. RC phase shift oscillator ii. Wein bridge oscillator

Not a reason for the use of an antenna coupler. A. To make the antenna look resistive B. To provide the output amplifier with the correct load impedance C. To discriminate against harmonics D. To prevent re-radiation of the local oscillator

Description : Not a reason for the use of an antenna coupler. A. To make the antenna look resistive B. To provide the output amplifier with the correct load impedance C. To discriminate against harmonics D. To prevent re-radiation of the local oscillator

Last Answer : D. To prevent re-radiation of the local oscillator

A final amplifier of a radio transmitter draws 250 mA of plate current when the plate supply voltage is 1400 volts. If the plate circuit efficiency is 80% and the transmitter is connected to an antenna having a feed impedance of 70 ohms, what is the antenna current at the feed-point? A. 4.0 A B. 2.2 A C. 1.25 A D. 2.0 A

Description : A final amplifier of a radio transmitter draws 250 mA of plate current when the plate supply voltage is 1400 volts. If the plate circuit efficiency is 80% and the transmitter is connected to an antenna having a feed impedance of 70 ohms, ... at the feed-point? A. 4.0 A B. 2.2 A C. 1.25 A D. 2.0 A

Last Answer : D. 2.0 A

Which of the following antennas is used for testing and adjusting a transmitter for proper modulation, amplifier operation and frequency accuracy? A. Elementary B. Real C. Isotropic D. Dummy

Description : Which of the following antennas is used for testing and adjusting a transmitter for proper modulation, amplifier operation and frequency accuracy? A. Elementary B. Real C. Isotropic D. Dummy

Last Answer : D. Dummy

Which circuit contributes most of the noise in a receiver? A. IF amplifier B. Demodulator C. AF amplifier D. Mixer

Description : Which circuit contributes most of the noise in a receiver? A. IF amplifier B. Demodulator C. AF amplifier D. Mixer

Last Answer : D. Mixer

Calculate the noise figure of the receiver whose RF amplifier has an input resistance of 1000Ω and an equivalent shot-noise resistance of 2000Ω, a gain of 25 and load resistance of 125 kΩ. Given that the bandwidth is 1.0MHz and the temperature is 20˚C, and that the receiver is connected to an antenna with an impedance of 75Ω. A. 30.3 B. 3.03 C. 303 D. .303

Description : Calculate the noise figure of the receiver whose RF amplifier has an input resistance of 1000Ω and an equivalent shot-noise resistance of 2000Ω, a gain of 25 and load resistance of 125 kΩ. Given that the bandwidth is 1. ... to an antenna with an impedance of 75Ω. A. 30.3 B. 3.03 C. 303 D. .303

Last Answer : A. 30.3

Calculated the noise figure of the amplifier whose Req equals 2518Ω (RT=600Ω) if its driven by a generator whose output impedance is 50Ω. A. 39.4 B. 3.94 C. 394 D. 0.394

Description : Calculated the noise figure of the amplifier whose Req equals 2518Ω (RT=600Ω) if its driven by a generator whose output impedance is 50Ω. A. 39.4 B. 3.94 C. 394 D. 0.394

Last Answer : A. 39.4

Indicate the false statement. Noise figure is defined as A. the ratio of the S/N power supplied at the input terminal of a receiver or amplifier to the S/N power supplied to the output or load resistor B. noise factor expressed in decibels C. an unwanted form of energy tending to interfere with the proper and easy reception and reproduction of wanted signal D. S/N of an ideal system divided by S/N at the output of the receiver or amplifier under test, both working at the same temperature over the same bandwidth and fed from the same source

Description : Indicate the false statement. Noise figure is defined as A. the ratio of the S/N power supplied at the input terminal of a receiver or amplifier to the S/N power supplied to the output or ... under test, both working at the same temperature over the same bandwidth and fed from the same source

Last Answer : C. an unwanted form of energy tending to interfere with the proper and easy reception and reproduction of wanted signals

The noise output of a resistor is amplified by a noiseless amplifier having a gain of 60 and a bandwidth of 20 kHz. A meter connected at the output of the amplifier reads 1mV RMS. If the bandwidth of the amplifier is reduced to 5kHz, its gain remaining constant, what does the meter read now? A. 0.5 mV B. 0.5 µV C. 5.0 mV D. 5.0 µV

Description : The noise output of a resistor is amplified by a noiseless amplifier having a gain of 60 and a bandwidth of 20 kHz. A meter connected at the output of the amplifier reads 1mV RMS. If the bandwidth of the amplifier is reduced to ... does the meter read now? A. 0.5 mV B. 0.5 µV C. 5.0 mV D. 5.0 µV

Last Answer : A. 0.5 mV

The first stage of a two-stage amplifier has a voltage gain of 10, a 600 Ω input resistor, a 1600Ω equivalent noise resistance and 27kΩ output resistor. For the second stage, these values are 25, 81kΩ, 19kΩ, and 1MΩ, respectively. Calculate the equivalent input-noise resistance of this two stage amplifier. A. 2,518 kΩ B. 2,518 Ω C. 251.8 Ω D. 12,518 Ω

Description : The first stage of a two-stage amplifier has a voltage gain of 10, a 600 Ω input resistor, a 1600Ω equivalent noise resistance and 27kΩ output resistor. For the second stage, these values are 25, 81kΩ, 19kΩ, and 1MΩ, ... this two stage amplifier. A. 2,518 kΩ B. 2,518 Ω C. 251.8 Ω D. 12,518 Ω

Last Answer : B. 2,518 Ω

An amplifier operating over the frequency range of 455 to 460 kHz has a 200 kΩ input resistor. What is the RMS noise voltage at the input to this amplifier if the ambient temperature is 17˚C ? A. 40 µV B. 4.0 µV C. 400 µV

Description : An amplifier operating over the frequency range of 455 to 460 kHz has a 200 kΩ input resistor. What is the RMS noise voltage at the input to this amplifier if the ambient temperature is 17˚C ? A. 40 µV B. 4.0 µV C. 400 µV

Last Answer : B. 4.0 µV

What is the reliable measurement for comparing amplifier noise characteristics? A. Thermal agitation noise B. Noise factor C. Noise margin D. Signal-to-noise

Description : What is the reliable measurement for comparing amplifier noise characteristics? A. Thermal agitation noise B. Noise factor C. Noise margin D. Signal-to-noise

Last Answer : B. Noise factor

What part or section of a TV receiver that separates the sound and video signals? A. IF stage B. Video amplifier C. Video detector D. Burst separator

Description : What part or section of a TV receiver that separates the sound and video signals? A. IF stage B. Video amplifier C. Video detector D. Burst separator

Last Answer : C. Video detector

When measuring a transmitter’s frequency against a suitable standard, the frequency to be measured is taken from the A. oscillator stage B. intermediate amplifier C. buffer stage D. final RF stage

Description : When measuring a transmitter’s frequency against a suitable standard, the frequency to be measured is taken from the A. oscillator stage B. intermediate amplifier C. buffer stage D. final RF stage

Last Answer : D. final RF stage

What is the meaning of forward power? A. The power traveling from the transmitter to the antenna. B. The power radiated from the top of an antenna system. C. The power produced during the positive half of an RF cycle. D. The power used to drive a linear amplifier.

Description : What is the meaning of forward power? A. The power traveling from the transmitter to the antenna. B. The power radiated from the top of an antenna system. C. The power produced during the positive half of an RF cycle. D. The power used to drive a linear amplifier.

Last Answer : A. The power traveling from the transmitter to the antenna.

What establishes the receiver bandwidth? A. RF amplifier B. Mixer C. Local oscillator D. IF amplifier

Description : What establishes the receiver bandwidth? A. RF amplifier B. Mixer C. Local oscillator D. IF amplifier

Last Answer : D. IF amplifier

What consists the front-end circuit of a VHF TV superheterodyne receiver? A. Mixer, RF amplifier and AFC? B. RF amplifier, Band pass filter and mixer C. Local oscillator, mixer and RF amplifier D. Local oscillator, AGC and antenna

Description : What consists the front-end circuit of a VHF TV superheterodyne receiver? A. Mixer, RF amplifier and AFC? B. RF amplifier, Band pass filter and mixer C. Local oscillator, mixer and RF amplifier D. Local oscillator, AGC and antenna

Last Answer : C. Local oscillator, mixer and RF amplifier

One of the following is a high powered RF ac basic transmitter that has two or more stages, the oscillator stage which determines the frequency opereation and RF amplifier stage orstages that develop the high power output. The purpose of which is to develop a good frequency stability. A. Goldsmith B. MOPA C. Alexanderson D. Hartley

Description : One of the following is a high powered RF ac basic transmitter that has two or more stages, the oscillator stage which determines the frequency opereation and RF amplifier stage orstages that develop the ... to develop a good frequency stability. A. Goldsmith B. MOPA C. Alexanderson D. Hartley

Last Answer : B. MOPA

Determine the lower half-power frequency of a class-C amplifier having upper half-power frequency of 10.025 MHz, a resonant frequency 5 MHz and a circuit Q of 10. A. 1.0025 MHz B. 10.525 MHz C. 0.5 MHz D. 10 MHz

Description : Determine the lower half-power frequency of a class-C amplifier having upper half-power frequency of 10.025 MHz, a resonant frequency 5 MHz and a circuit Q of 10. A. 1.0025 MHz B. 10.525 MHz C. 0.5 MHz D. 10 MHz

Last Answer : A. 1.0025 MHz

Which of the following parts of the radio receiver represent the component that extracts the desire RF signal from the electromagnetic wave? A. AF amplifier B. Antenna C. Detector D. Crystal

Description : Which of the following parts of the radio receiver represent the component that extracts the desire RF signal from the electromagnetic wave? A. AF amplifier B. Antenna C. Detector D. Crystal

Last Answer : B. Antenna

One of the following is a possible cause of an abrupt frequency variation in a self exited transmitter oscillator circuits resulting to a poor frequency stability to hold a constant frequency oscillation. A. Heating and expansion of oscillator coil B. DC and RF ac heating of resistors which cause change in values C. Heating of capacitor in the oscillatorD. Loose connections in the oscillator, amplifier, or antenna circuits.

Description : One of the following is a possible cause of an abrupt frequency variation in a self exited transmitter oscillator circuits resulting to a poor frequency stability to hold a constant frequency ... capacitor in the oscillator D. Loose connections in the oscillator, amplifier, or antenna circuits.

Last Answer : D. Loose connections in the oscillator, amplifier, or antenna circuits.

Refers to one of the front end circuit of a VHF TV superheterodyne receiver which is usually a separate circuit coupled to the mixer. A. Antenna feed B. AGC C. RF amplifier D. Local oscillator

Description : Refers to one of the front end circuit of a VHF TV superheterodyne receiver which is usually a separate circuit coupled to the mixer. A. Antenna feed B. AGC C. RF amplifier D. Local oscillator

Last Answer : D. Local oscillator

Referred to an oscillator signal “leak through” from a properly neutralized amplifier such as a master oscillator power amplifier. A. Carrier B. Stray signal C. Back wave D. Loss wave

Description : Referred to an oscillator signal “leak through” from a properly neutralized amplifier such as a master oscillator power amplifier. A. Carrier B. Stray signal C. Back wave D. Loss wave

Last Answer : C. Back wave

Which of the following is one of the possible causes for a slow drift of frequency in a self exited transmitter oscillator circuits resulting to a poor frequency stability? A. Poor soldered connections B. Power supply voltage changes C. Loose connections in the oscillator, amplifier, or antenna circuits D. DC and RF heating of resistors, causing then to change values.

Description : Which of the following is one of the possible causes for a slow drift of frequency in a self exited transmitter oscillator circuits resulting to a poor frequency stability? A. Poor soldered connections ... , or antenna circuits D. DC and RF heating of resistors, causing then to change values.

Last Answer : D. DC and RF heating of resistors, causing then to change values.

Referred to as the stage in the radio receiver that contributes most of the noise. A. IF amplifier B. Supply stage C. Speaker D. Mixer

Description : Referred to as the stage in the radio receiver that contributes most of the noise. A. IF amplifier B. Supply stage C. Speaker D. Mixer

Last Answer : D. Mixer

Best describe as an amplifier used in radio telephony. A. Magnifier B. Class B C. Class C D. Class A

Description : Best describe as an amplifier used in radio telephony. A. Magnifier B. Class B C. Class C D. Class A

Last Answer : C. Class C

What do you call the single booster installed on the antenna dish of satellite receiver? A. Low noise amplifier B. Single amplifier C. Noise amplifier D. Rectifier

Description : What do you call the single booster installed on the antenna dish of satellite receiver? A. Low noise amplifier B. Single amplifier C. Noise amplifier D. Rectifier

Last Answer : A. Low noise amplifier