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FCC EXTRA Exam Question Pool. Subelement 4BG. Practical Circuits. 4 Questions. --------------------------------------------------- 4BG 1A1 D What is a flip-flop circuit? A. A binary sequential logic element with one stable state B. A binary sequential logic element with eight stable states C. A binary sequential logic element with four stable states D. A binary sequential logic element with two stable states 4BG 1A2 A How many bits of information can be stored in a single flip-flop circuit? A. 1 B. 2 C. 3 D. 4 4BG 1A3 C What is a bistable multivibrator circuit? A. An "AND" gate B. An "OR" gate C. A flip-flop D. A clock 4BG 1A4 C How many output changes are obtained for every two trigger pulses applied to the input of a bistable T flip-flop circuit? A. No output level changes B. One output level change C. Two output level changes D. Four output level changes 4BG 1A5 C The frequency of an ac signal can be divided electronically by what type of digital circuit? A. A free-running multivibrator B. An OR gate C. A bistable multivibrator D. A astable multivibrator 4BG 1A6 C What type of digital IC is also known as a latch? A. A decade counter B. An OR gate C. A flip-flop D. An op-amp 4BG 1A7 B How many flip-flops are required to divide a signal frequency by 4? A. 1 B. 2 C. 4 D. 8 4BG 1B1 D What is an astable multivibrator? A. A circuit that alternates between two stable states B. A circuit that alternates between a stable state and an unstable state C. A circuit set to block either a 0 pulse or a 1 pulse and pass the other D. A circuit that alternates between two unstable states 4BG 1B2 A What is an monostable multivibrator? A. A circuit that can be switched momentarily to the opposite binary state and then returns after a set time to its original state B. A "clock" circuit circuit that produces a continuous square wave oscillating between 1 and 0 C. A circuit designed to store one bit of data in either the 0 or the 1 configuration D. A circuit that maintains a constant output voltage, regardless of variations in the input voltage 4BG 1C1 A What is an AND gate? A. A circuit that produces a logic "1" at its output only if all inputs are logic "1" B. A circuit that produces a logic "0" at its output only if all inputs are logic "1" C. A circuit that produces a logic "1" at its output if only one input is a logic "1" D. A circuit that produces a logic "1" at its output if all inputs are logic "0" 4BG 1C2 A What is the schematic symbol for an AND gate? ┌─────── \ │ \ A. ───┤ \ B. │ \ │ ├─── │ \ ───┤ / ────┤ ├──── └─────── / │ / │ / │ / ┌───────\ \ \ C. ───┤ \ D. │ \ │ ├─── │ \ ───┤ / ────┤ ├O─── / / │ / └───────/ │ / 4BG 1C3 D What is a NAND gate? A. A circuit that produces a logic "0" at its output only when all inputs are logic "0" B. A circuit that produces a logic "1" at its output only when all inputs are logic "1" C. A circuit that produces a logic "0" at its output if some but not all of its inputs are logic "1" D. A circuit that produces a logic "0" at its output only when all inputs are logic "1" 4BG 1C4 B What is the schematic symbol for an NAND gate? ┌───────\ \ \ ┌─────── \ A. ──O┤ \ B. ───┤ \ │ ├O── │ ├O── ──O┤ / ───┤ / / / └─────── / └───────/ . ┌───────\ \ \ ┌─────── \ C. ───┤ \ D. ──O┤ \ │ ├O── │ ├O── ───┤ / ──O┤ / / / └─────── / └───────/ 4BG 1C5 A What is an OR gate? A. A circuit that produces a logic "1" at its output if any input is logic "1" B. A circuit that produces a logic "0" at its output if any input is logic "1" C. A circuit that produces a logic "0" at its output if all inputs are logic "1" D. A circuit that produces a logic "1" at its output if all inputs are logic "0" 4BG 1C6 D What is the schematic symbol for an OR gate? ┌─────── \ │ \ A. ───┤ \ B. │ \ │ ├─── ────┤ ├O─── ───┤ / │ / └─────── / │ / . . │ \ ┌───────\ │ \ \ \ C. │ \ D. ───┤ \ ────┤ ├──── │ ├─── │ / ───┤ / │ / / / │ / └───────/ 4BG 1C7 C What is a NOR gate? A. A circuit that produces a logic "0" at its output only if all inputs are logic "0" B. A circuit that produces a logic "1" at its output only if all inputs are logic "1" C. A circuit that produces a logic "0" at its output if any or all inputs are logic "1" D. A circuit that produces a logic "1" at its output if some but not all inputs are logic "1" 4BG 1C8 D What is the schematic symbol for an NOR gate? ┌─────── \ ┌───────\ A. ───┤ \ B. \ \ │ ├O── ───┤ \ ───┤ / │ ├─── └─────── / ───┤ / / / └───────/ . ┌───────\ │ \ \ \ C. │ \ D. ───┤ \ ───O┤ ├──── │ ├O── │ / ───┤ / │ / / / └───────/ 4BG 1C9 A What is a NOT gate? A. A circuit that produces a logic "0" at its output when the input is logic "1" and vice versa B. A circuit that does not allow data transmission when its input is high C. A circuit that allows data transmission only when its input is high D. A circuit that produces a logic "1" at its output when the input is logic "1" and vice versa 4BG 1C10 A What is the schematic symbol for an NOT gate? ┌───────\ │ \ \ \ A. │ \ B. ──O┤ \ ────┤ ├O─── │ ├─── │ / ──O┤ / │ / / / └───────/ . ┌─────── \ ┌─────── \ C. ───┤ \ D. ──O┤ \ │ ├─── │ ├─── ───┤ / ──O┤ / └─────── / └─────── / 4BG 1D1 C What is a truth table? A. A table of logic symbols that indicate the high logic states of an op-amp B. A diagram showing logic states when the digital device's output is true C. A list of input combinations and their corresponding outputs that characterizes a digital device's function D. A table of logic symbols that indicates the low logic states of an op-amp 4BG 1D2 D In a positive-logic circuit, what level is used to represent a logic 1? A. A low level B. A positive-transition level C. A negative-transition level D. A high level 4BG 1D3 A In a positive-logic circuit, what level is used to represent a logic 0? A. A low level B. A positive-transition level C. A negative-transition level D. A high level 4BG 1D4 A In a negative-logic circuit, what level is used to represent a logic 1? A. A low level B. A positive-transition level C. A negative-transition level D. A high level 4BG 1D5 D In a negative-logic circuit, what level is used to represent a logic 0? A. A low level B. A positive-transition level C. A negative-transition level D. A high level 4BG 2A1 D What is a crystal-controlled marker generator? A. A low-stability oscillator that "sweeps" through a band of frequencies B. An oscillator often used in aircraft to determine the craft's location relative to the inner and outer markers at airports C. A high-stability oscillator whose output frequency and amplitude can be varied over a wide range D. A high-stability oscillator that generates a series of reference signals at known frequency intervals 4BG 2A2 C What additional circuitry is required in a 100-kHz crystal-controlled marker generator to provide markers at 50 and 25 kHz? A. An emitter-follower B. Two frequency multipliers C. Two flip-flops D. A voltage divider 4BG 2B1 D What is the purpose of a prescaler circuit? A. It converts the output of a JK flip-flop to that of a RS flip-flop B. It multiplies an HF signal so a low-frequency counter can display the operating frequency C. It prevents oscillation in a low frequency counter circuit D. It divides an HF signal so a low-frequency counter can display the operating frequency 4BG 2B2 A What does the accuracy of a frequency counter depend on? A. The internal crystal reference B. A voltage-regulated power supply C. Accuracy of the ac input frequency to the power supply D. Proper balancing of the power-supply diodes 4BG 2B3 B How many states does a decade counter digital IC have? A. 6 B. 10 C. 15 D. 20 4BG 2B4 B What is the function of a decade counter digital IC? A. Decode a decimal number for display on a seven-segment LED display B. Produce one output pulse for every ten input pulses C. Produce ten output pulses for every input pulse D. Add two decimal numbers 4BG 3A1 D What are the advantages of using an op-amp instead of LC elements in an audio filter? A. Op-amps are more rugged and can withstand more abuse than can LC elements B. Op-amps are fixed at one frequency C. Op-amps are available in more styles and types than are LC elements D. Op-amps exhibit gain rather than insertion loss 4BG 3A2 B What determines the gain and frequency characteristics of an op-amp RC active filter? A. Values of capacitances and resistances built into the op-amp B. Values of capacitances and resistances external to the op-amp C. Voltage and frequency of dc input to the op-amp power supply D. Regulated dc voltage output from the op-amp power 4BG 3A3 D What are the principle uses of an op-amp RC active filter in amateur circuitry? A. Op-amp circuits are used as high-pass filters to block RFI at the input to receivers B. Op-amp circuits are used as low-pass filters between transmitters and transmission lines C. Op-amp circuits are used as filters for smoothing power- supply output D. Op-amp circuits are used as audio filters for receivers 4BG 3B1 C What type of capacitors should be used in an op-amp RC active filter circuit? A. Electrolytic B. Disc ceramic C. Polystyrene D. Paper dielectric 4BG 3B2 A How can unwanted ringing and audio instability be prevented in a multisection op-amp RC audio filter circuit? A. Restrict both gain and Q B. Restrict gain, but increase Q C. Restrict Q, but increase gain D. Increase both gain and Q 4BG 3B3 D Where should an op-amp RC active audio filter be placed in an amateur receiver? A. In the IF strip, immediately before the detector B. In the audio circuitry, immediately before the speaker or phone jack C. Between the balanced modular and frequency multiplier D. In the low-level audio stages 4BG 3B4 A What parameter must be selected when designing an audio filter using an OP-amp? A. Bandpass characteristics B. Desired current gain C. Temperature coefficient D. Output-offset overshoot 4BG 4A1 D What factors determine the sensitivity of a receiver? A. Dynamic range and third-order intercept B. Cost and availability C. Intermodulation distortion and dynamic range D. Bandwidth and noise figure 4BG 4A2 A What is the limiting condition for sensitivity in a communications receiver? A. The noise floor of the receiver B. The power-supply output ripple C. The two-tone intermodulation distortion D. The input impedance to the detector 4BG 4A3 B What is the theoretical minimum noise floor of a receiver with a 400-Hertz bandwidth? A. -141 dBm B. -148 dBm C. -174 dBm D. -180 dBm 4BG 4B1 B How can selectivity be achieved in the front-end circuitry of a communications receiver? A. By using an audio filter B. By using a preselector C. By using an additional RF amplifier stage D. By using an additional IF amplifier stage 4BG 4B2 B A receiver selectivity of 2.4 kHz in the IF circuitry is optimum for what type of amateur signals? A. CW B. SSB voice C. Double-sideband AM voice D. FSK RTTY 4BG 4B3 D What occurs during CW reception if too narrow a filter bandwidth is used in the IF stage of a receiver? A. Undesired signals will reach the audio stage B. Output-offset overshoot C. Cross-modulation distortion D. Filter ringing 4BG 4B4 B What degree of selectivity is desirable in the IF circuitry of an amateur RTTY receiver? A. 100 Hz B. 300 Hz C. 6000 Hz D. 2400 Hz 4BG 4B5 B A receiver selectivity of 10 kHz in the IF circuitry is optimum for what type of amateur signals? A. SSB voice B. Double-sideband AM C. CW D. FSK RTTY 4BG 4B6 B What degree of selectivity is desirable in the IF circuitry of a single-sideband phone receiver? A. 1 kHz B. 2.4 kHz C. 4.2 kHz D. 4.8 kHz 4BG 4B7 B What is an undesirable effect of using too wide a filter bandwidth in the IF section of a receiver? A. Output-offset overshoot B. Undesired signals will reach the audio stage C. Thermal-noise distortion D. Filter ringing 4BG 4B8 A How should the filter bandwidth of a receiver IF section compare with the bandwidth of the received signal? A. Filter bandwidth should be slightly greater than the received-signal bandwidth B. Filter bandwidth should be approximately half the received- signal bandwidth C. Filter bandwidth should be approximately two times the received-signal bandwidth D. Filter bandwidth should be approximately four times the received-signal bandwidth 4BG 4B9 D What degree of selectivity is desirable in the IF circuitry of an emission FM phone receiver? A. 1 kHz B. 2.4 kHz C. 4.2 kHz D. 15 kHz 4BG 4B10 D How can selectivity be achieved in the IF circuitry of a communications receiver? A. Incorporate a means of varying the supply voltage to the local oscillator circuitry B. Replace the standard JFET mixer with a bipolar transistor followed by a capacitor of the proper value C. Remove AGC action from the IF stage and confine it to the audio stage only D. Incorporate a high-Q filter 4BG 4C1 C What is meant by the dynamic range of a communications receiver? A. The number of kHz between the lowest and the highest frequency to which the receiver can be tuned B. The maximum possible undistorted audio output of the receiver, referenced to one milliwatt C. The ratio between the minimum discernible signal and the largest tolerable signal without causing audible distortion products D. The difference between the lowest-frequency signal and the highest-frequency signal detectable without moving the tuning dial 4BG 4C2 D What is the term for the ratio between the largest tolerable receiver input signal and the minimum discernible signal? A. Intermodulation distortion B. Noise floor C. Noise figure D. Dynamic range 4BG 4C3 A What type of problems are caused by poor dynamic range in a communications receiver? A. Cross-modulation of the desired signal and desensitization from strong adjacent signals B. Oscillator instability requiring frequent retuning, and loss of ability to recover the opposite sideband, should it be transmitted C. Cross-modulation of the desired signal and insufficient audio power to operate the speaker D. Oscillator instability severe audio distortion of all but the strongest received signals 4BG 4C4 B The ability of a communications receiver to perform well in the presence of strong signals outside the amateur band of interest is indicated by what parameter? A. Noise figure B. Blocking dynamic range C. Signal-to-noise ratio D. Audio output 4BG 4D1 C What is meant by the term noise figure of a communications receiver? A. The level of noise entering the receiver from the antenna B. The relative strength of a received signal 3 kHz removed from the carrier frequency C. The level of noise generated in the front end and succeeding stages of a receiver D. The ability of a receiver to reject unwanted signals at frequencies close to the desired one 4BG 4D2 C Which stage of a receiver primarily establishes its noise figure? A. The audio stages B. The IF strip C. The RF stage D. The local oscillator 4BG 5A1 A What is an inverting op-amp? A. An operational amplifier circuit connected such that the input and output signals are 180 degrees out of phase B. An operational amplifier circuit connected such that the input and output signals are in phase C. An operational amplifier circuit connected such that the input and output are 90 degrees out of phase D. An operational amplifier circuit connected such that the input impedance is held at zero, while the output impedance is high 4BG 5B1 B What is an noninverting op-amp? A. An operational amplifier circuit connected such that the input and output signals are 180 degrees out of phase B. An operational amplifier circuit connected such that the input and output signals are in phase C. An operational amplifier circuit connected such that the input and output are 90 degrees out of phase D. An operational amplifier circuit connected such that the input impedance is held at zero, while the output impedance is high 4BG 5C1 D What voltage gain can be expected from the circuit in Figure 4BG-5 when R1 is 1000 ohms and Rf is 100 kilohms? A. 0.01 B. 1 C. 10 D. 100 ┌────/\/\/\/\/\/\───┐ │ Rf │ R1 │ / \ │ O────/\/\/\/\/\/\┴───┤ - \ │ │ \ │ │ ├─────┴───O │ / FIGURE 4BG-5 ┌───┤ + / O │ \ / │ __│___ __│___ / / / / / / 4BG 5C2 C What voltage gain can be expected from the circuit in Figure 4BG-5 when R1 is 1800 ohms and Rf is 68 kilohms? A. 1 B. 0.03 C. 38 D. 76 ┌────/\/\/\/\/\/\───┐ │ Rf │ R1 │ / \ │ O────/\/\/\/\/\/\┴───┤ - \ │ │ \ │ │ ├─────┴───O │ / FIGURE 4BG-5 ┌───┤ + / O │ \ / │ __│___ __│___ / / / / / / 4BG 5C3 B What voltage gain can be expected from the circuit in Figure 4BG-5 when R1 is 3300 ohms and Rf is 47 kilohms? A. 28 B. 14 C. 7 D. 0.07 ┌────/\/\/\/\/\/\───┐ │ Rf │ R1 │ / \ │ O────/\/\/\/\/\/\┴───┤ - \ │ │ \ │ │ ├─────┴───O │ / FIGURE 4BG-5 ┌───┤ + / O │ \ / │ __│___ __│___ / / / / / / 4BG 5C4 C What voltage gain can be expected from the circuit in Figure 4BG-5 when R1 is 10 ohms and Rf is 47 kilohms? A. 0.00021 B. 9400 C. 4700 D. 2350 ┌────/\/\/\/\/\/\───┐ │ Rf │ R1 │ / \ │ O────/\/\/\/\/\/\┴───┤ - \ │ │ \ │ │ ├─────┴───O │ / FIGURE 4BG-5 ┌───┤ + / O │ \ / │ __│___ __│___ / / / / / / 4BG 5D1 D How does the gain of a theoretically ideal operational amplifier vary with frequency? A. The gain increases linearly with increasing frequency B. The gain decreases linearly with increasing frequency C. The gain decreases logarithmically with increasing frequency D. The gain does not vary with frequency 4BG 6.1 C What determines the input impedance in a FET common-source amplifier? A. The input impedance is essentially determined by the resistance between the drain and substrate B. The input impedance is essentially determined by the resistance between the source and drain C. The input impedance is essentially determined by the gate biasing network D. The input impedance is essentially determined by the resistance between the source and substrate 4BG 6.2 A What determines the output impedance in a FET common-source amplifier? A. The output impedance is essentially determined by the drain resistor B. The output impedance is essentially determined by the input impedance of the FET C. The output impedance is essentially determined by the drain supply voltage D. The output impedance is essentially determined by the gate supply voltage 4BG 7.1 A What frequency range will be tuned by the circuit in Figure 4BG-7 when L is 10 microhenrys, Cf is 156 picofarads, and Cv is 50 picofarads maximum and 2 picofarads minimum? A. 3508 through 4004 kHz B. 6998 through 7360 kHz C. 13.396 through 14.402 MHz D. 49.998 through 54.101 MHz ┌───────────┬────────────┬───────O └──┐ │ │ ─┐ ──┤ │ │ / ──┤ ───┴─── ───┴─── O────────┤ ───┬─── ───┬─── ──┤ │ Cf / │ Cv ──┤ L │ / │ FIGURE 4BG-7 ┌──┘ │ │ O─────┴───────────┴────────────┴───────O 4BG 7.2 A What frequency range will be tuned by the circuit in Figure 4BG-7 when L is 30 microhenrys, Cf is 200 picofarads, and Cv is 80 picofarads maximum and 10 picofarads minimum? A. 1737 through 2005 kHz B. 3507 through 4004 kHz C. 7002 through 7354 kHz D. 14.990 through 15.020 MHz ┌───────────┬────────────┬───────O └──┐ │ │ ─┐ ──┤ │ │ / ──┤ ───┴─── ───┴─── O────────┤ ───┬─── ───┬─── ──┤ │ Cf / │ Cv ──┤ L │ / │ FIGURE 4BG-7 ┌──┘ │ │ O─────┴───────────┴────────────┴───────O 4BG 8.1 C What is the purpose of a bypass capacitor? A. It increase the resonant frequency of the circuit B. It removes direct current from the circuit by shunting DC to ground C. It removes alternating current by providing a low impedance path to ground D. It acts as a voltage divider 4BG 8.2 A What is the purpose of a coupling capacitor? A. It blocks direct current and passes alternating current B. It blocks alternating current and passes direct current C. It increases the resonant frequency of the circuit D. It decreases the resonant frequency of the circuit -------------------------------------------------- End of Subelement 4BG.