WAVE SHAPING CICUITS AND MULTIVIBRATORS
1. Give two applications of bistable
multivibrators
·
Used to
generate symmetrical square wave. This is possible by using triggering pulses
of equal interval, corresponding to the frequency required.
·
Used as
a memory element in shift registers,counters,etc,.
·
Used for
the performance of many digital operations like counting and storing of digital
information.
·
Can be
used as a frequency divider
2. How does a diode act as a comparator?
A Comparator Circuit is used to identify the
instant at which the arbitrary input waveform attains a particular reference
level. Basically it is a clipper circuit. A simple diode comparator and its
equivalent circuit is given as
3. What is meant by clipper circuit?
The electronic circuits which are used to clip
off the unwanted portion of the waveform, without distorting the remaining part
of the waveform are called clipper circuits.
4. What is the 'tilt' applicable to RC
circuits? Give an expression for tilt.
In high pass RC network, Tilt is defined as the
decay in the amplitude of the output voltage waveform, when the input maintains
its level constant.
Percentage of tilt is given by
5. What type of distortion is observed in
astable multivibrator?
It can be seen that, in the collector waveforms
shown in the figure there is certain distortion present. Instead of [Vc1, Vc2]
exact square wave, we are getting the vertical rising edges little bit rounded.
This is called rounding. For a
square wave output such a rounding is undesirable and must be eliminated.
6. What is meant by clamper circuit?
The electronic circuits which are used to add a
dc level as per the requirement to the ac output signal are called clamper
circuits.
It is also known as dc inserter or dc restorer.
7.
Give two applications of Schmitt Trigger
circuit..
· It is used as a amplitude
comparator
· It can be used as a squaring
circuit.
· It can be used as a sine wave to square wave
converter
8.
Why do we call astable multivibrator as free
running multivibrator?
An astable multivibrator is called free running
multivibrator because it generates square waves of its own without any external
triggering pulse.
9. Define the threshold points in a Schmitt
trigger circuit.
·
Schmitt
trigger is a type of comparator with two different threshold voltage levels on
points (UTP, LTP).
·
Whenever
the input signal goes over the high threshold levels, the output of the
comparator is switched high. The output will remain in this same state as long
as the input voltage is above the low threshold level.
·
When the
input voltage goes below this level, the output will switch. These threshold
voltage levels are called threshold points.
10. What
is a regenerative comparator? Give example circuit.
Regenerative comparator is a circuit, compares
its input voltage to a “threshold voltage”, because it has two threshold
voltages(the upper and lower trigger voltages). The threshold voltage depends
on the output state. If the input voltage is higher than the upper trigger
voltage, the output will be high.
A small amount of the output voltage is
effectively added to the input voltage before it is compared to a fixed
threshold. So it uses positive (or) regenerative feedback.
E.g.: Schmitt Trigger
11.
Distinguish between symmetrical and unsymmetrical triggering methods.
Symmetrical triggering uses only one trigger
input and unsymmetrical triggering uses two trigger input.
12.
Why Monostable multivibrator is also called as
delay circuit?
Used to introduce time delay as gate width is
adjustable.
13.
Determine the value of capacitors to be used in
an astable multivibrator to provide a train of pulse of 4 μs wide
at a repetition rate okf 80KHz if R1=R2=10K.
14.
A 20 KHz, 75% duty cycle square wave is used to
trigger continuously, a monostable multivibrator with triggered pulse duration
of 5µs. What will be the duty cycle of the output of the monostable
multivibrator?
15.
A RC low pass circuit has R=1.5Kohm and
C=0.2micro farad. What is the rise time of the output when excited by a step
input.
16.
In a low pass RC circuit, rise time is 35 nano
seconds. What is the bandwidth that can be obtained using the circuit?
17.
Determine the value of capacitors to be used in
an astable multivibrator to provide a train of pulse 2µs wide at a repetition
rate of 75KHz with R1=R2=10KHz.
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