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You Are On Multi Choice Question Bank SET 978

48901. An astable multivibrator requires:





48902. A crystal demonstrates the ________ effect when a mechanical force across the crystal causes a small voltage to be generated.





48903. What is the difference between an astable multivibrator and a monostable multivibrator?





48904. Is there any limit to the number of times that a 74123 can be retriggered?



48905. Determine tHI and tLO for the circuit given below.





48906. The output of the astable circuit ________.





48907. If a diode is connected across resistor RB (positive end up) in the given figure, what is the new duty cycle of the output waveform?





48908. Design a circuit using a 74121 to convert a 33-kHz, 30% duty cycle waveform to a 33-kHz, 60% duty cycle waveform.





48909. What controls the output pulse width of a one shot?





48910. Does the 74123 one shot have an internal timing resistor?



48911. In a typical IC monostable multivibrator circuit, at the falling edge of the trigger input, the output switches HIGH for a period of time determined by the ________.





48912. A monostable 555 timer has the following number of stable states:





48913. What is the difference between a retriggerable one shot and a nonretriggerable one shot?





48914. Triggering a retriggerable one shot during pulse generation will:





48915. What is the duty cycle of the waveform at the output of the circuit given below?





48916. The monostable multivibrator circuit is not an oscillator because ________.





48917. A retriggerable one shot has a pulse of 10 ms. 3 ms after being triggered, another trigger pulse is applied. The resulting output pulse will be ________ ms.





48918. What is the pulse width of the output of a 74123 if an external 4.7-k resistor and a 0.022-F capacitor are used?





48919. To obtain a 50% duty cycle in an astable 555 timer circuit:





48920. What is another name for a bistable multivibrator?




48921. An astable 555 timer has the following number of stable states:





48922. Which mode of operation is being used when a 555 timer chip has two external resistors and an external capacitor?





48923. A 0.3-F capacitor has an initial charge of 2.7 V. If it is discharged through a 10-k resistor for 6.5 ms, how much voltage will be left across the capacitor?





48924. Is the circuit given below an astable multivibrator or a monostable multivibrator?



48925. Which of the following is NOT a characteristic of a retriggerable monostable multivibrator?





48926. What is the output pulse width of the waveform at the output of the circuit in the given figure?





48927. The pulse width out of a one-shot multivibrator increases when the:





48928. If Vcc of a 555 timer circuit is set to +10 V what is the level of output voltage from the circuit?





48929. If the resistor in the Schmitt trigger astable multivibrator is a variable resistor, what part of the output voltage waveform will change when the resistance is changed?





48930. When extremely critical timing is required, a quartz crystal can be used.



48931. In the 74121, which is nonretriggerable, any triggers that come in before the end of the timing cycle are ignored.



48932. A comparator simply outputs a HIGH or LOW based on a comparison of the voltage levels at its input.



48933. The 74S124 TTL chip is a voltage-controlled oscillator that will generate a specific frequency at Vout.



48934. A single Schmitt trigger inverter is all that is needed to build a simple astable multivibrator.



48935. The bistable multivibrator is an R-C flip-flop.



48936. When the 74123, a retriggerable monostable multivibrator device, ends its timing cycle it must be started all over again.



48937. Timing accuracy of more than eight significant digits can be easily achieved by using quartz crystals.



48938. A multivibrator is a circuit that changes between two digital levels on a continuous, free-running basis or on demand.



48939. A monostable multivibrator is commonly called a two shot.



48940. What is the function of the comparators in the 555 timer circuit?





48941. When a capacitor charges:





48942. The ________ is defined as the time the output is active divided by the total period of the output signal.





48943. A 22-k resistor and a 0.02-F capacitor are connected in series to a 5-V source. How long will it take the capacitor to charge to 3.4 V?





48944. What does the discharge transistor do in the 555 timer circuit?





48945. One hex digit is sometimes referred to as a(n):





48946. Which of the following is the most widely used alphanumeric code for computer input and output?





48947. If a typical PC uses a 20-bit address code, how much memory can the CPU address?





48948. Convert 59.7210 to BCD.





48949. Convert 8B3F16 to binary.





48950. Which is typically the longest: bit, byte, nibble, word?





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