UNIT-V
BLOCKING OSCILLATORS AND TIMEBASE GENERATORS
PART –A
1. Define rise time of a pulse. (MAY 2004)
The rise time is an important parameter related to this part of the response. It is defined by the time required by the pulse to rise from 10% of its amplitude to 90% of its amplitude.
2. Define sweep speed error or slope error. (JUN 2006)
It is the ratio of difference in slope at beginning and end of sweep to the initial value of slope.
3. Define displacement error. (JUN 2006&MAY 2011)
It is defined as the maximum difference between the actual sweep voltage and linear sweep which passes through the beginning and end points of the actual sweep.
4. What is UJT relaxation oscillator? (MAY 2010)
A unijunction transistor in conjunction with a capacitor and a charging resistor to construct an oscillator with an approximate ramp type output is known as UJT relaxation oscillator.
5. What is blocking oscillator? Why it is so called? (MAY 2008 , MAY 2010, NOV 2011)
A tuned collector oscillator circuit which uses a regenerative (positive) feedback via a pulse transformer,producing a single pulse or pulse train is called a blocking oscillator. The oscillator cuts itself OFF or BLOCKS after one or more cycles. Hence the name Blocking oscillator.
6. The transistor current sweep circuit will not provide precisely linear sweep. Why? (DEC 2006)
1. Lag of impulse term in current source 2.The inductance of iron core varies with current. 3. The driver transistor which provides the inductor current does not operate with sufficient linearity.
7. What is a pulse transformer? (MAY 2010)
A pulse transformer is basically a transformer, which couples a source of pulses of electrical energy to the load keeping the shape and other properties of pulse unchanged. The voltage level of the pulse can be raised or
lowered by designing the proper turns ratio for the pulse transformer.
8. State the applications of pulse transformer. (MAY 2010, MAY 2012)
Pulse transformer can be used to 1.change the amplitude and impedance level of a pulse 2.invert the polarity of a pulse 3.produce a pulse
in a circuit having negligible dc resistance 4.effect dc isolation between source and load 5.couple between stages of pulse amplifiers 6.differentiate a pulse 7. acts as a coupling element in certain pulse generating circuit.
9. What are the applications of blocking oscillator?(MAY 2008 & MAY 2011)
1. The blocking oscillator can be used as a frequency divider or conter.
2. The blocking oscillator as a low impedance switch can be used to discharge a capacitor quickly.
3. The output of the blocking oscillator can be used as a gating waveform with a very small mark-space ratio.
4.Blocking oscillator is capable of generating a pulse of large peak power. The average power is small since the duty cycle is low.
5. The astable circuit is used as a master oscillator to supply triggers for synchronizing a system of pulse type waveforms-square waves,sweep voltages etc.,
6. The monostable circuit is used to obtain abrupt pulses from a slowly varying
input triggering voltage.
7. Using a tertiary winding, output pulses of either polarity may be obtained
depending upon which end of the winding is grounded. Also, the output winding may be isolated from ground where required.
10. List various sweep circuits. Or What are the various methods of generating a time base waveform? (MAY 2008)
1.Exponential charging circuit 2.Constsnt-current charging circuit 3.Miller circuit 4.Phantastron circuit 5.Bootstrap circuit 6.Inductor circuit 7. Compensating networks.
11. What are current time base generator? (DEC 2005)
Current time base generator are the circuits which produce a current waveform which increases linearly with time. They are used in magnetic deflection system as television displays on large screen tubes and radars.
12. What are the drawbacks of time base generator? How can it be reduced? (DEC 2008)
The main drawback of time base generator is the high percentage slope speed error. It can be reduced by improving the linearity of the sweep by increasing the supply voltage or increasing the time constant of the circuit.
13. Define Restoration time or Flyback time. (JUN 2009, MAY 2012)
The time required for the return for the sweep voltage to the initial value is called the restoration time, the return time or fly back time
.
14. Define sweep time. (DEC 2008, JUN 2009, MAY 2012)
The period during which voltage increases linearly is called sweep time.
15. How can the linearization of trapezoidal voltage can be obtained? Or How is linearization achieved in current time base circuit? (JUN 2010)
It can be obtained by using three different circuit such as bootstrapping, using an op-amp or miller integrator and by changing a capacitor from a common current source such as common base transistor.
16. What is a sweep generator? (MAY 2010)
A sweep generator is a circuit that produces a sweep waveform. Sweep waveforms are those which have at least one portion in it with respect to time. There are different types of sweep generators like Miller time base sweep generator,Bootstrap sweep generator,etc.,
17. What do you mean by free running blocking oscillator?Why they are called so? (JUN 2010)
Astable blocking oscillator is called as free running blocking oscillator.It produces train of pulses when triggered. The pulse width and the duty cycle of the blocking oscillator output can be controlled as per the requirement. There are two types of astable blocking oscillators available:1.Diode controlled astable blocking oscillator 2.RC controlled astable blocking oscillator.
18.Define transmission error. (MAY 2004)
When a ramp voltage is transmitted through a high-pass RC network, its output falls away from the input.The transmission error is defined as the difference between the input and output divided by the input.
19. How will you form an astable blocking oscillator from a monostable blocking oscillator? (DEC 2005)
A diode network can be replaced by RC network to obtain RC controlled astable blocking oscillator. Such RC network can be added either in the emitter circuit of a monostable blocking oscillator or in the base circuit of a monostable blocking oscillator.
20. What do you mean by linear time base generator? (JUN 2007)
A linear time base generator is one that provides an output waveform, a portion of which exhibits a linear variation of voltage or current with time.
21. Compare diode controlled and RC controlled blocking oscillator. (MAY 2008)
Diode controlled blocking oscillator RC controlled blocking oscillator
1.Low duty cycle operation is possible. 1. Low duty cycle operation is impossible
2.Time period and frequency of oscillations can be easily varied by varying R1 or C1 2. Time period and frequency can not be easily varied. To change time period it is necessary to change the entire diode network to alter Vγ value.
3.The oscillations just before the pulse are missing and there is much less possibility of such oscillations. 3.There is possibility of oscillations just before the pulse for low duty cycle operation
4.The design equations are simpler. 4. The equations obtained are complicated and some are transcendental which require graphical solution.
5.The circuit is easy to design. 5. The circuit is difficult to design due to complexity of the equations.
6.The timing values are temperature dependent as diode network is temperature sensitive. 6. The time values does not depend on diode which is temperature sensitive. Hence the timing values are stable and temperature independent provided VBB >>Vγ of transistor and all the elements like R1,C1 etc., are temperature independent.
7. The overshoots after the pulse are absent and hence the waveforms are better and smooth. 7. In low duty cycle operation, voltage across capacitor discharges slowly. Due to this pulse at the collector has distorted waveform.
22. Give the uses of time base generator. (MAY 2011)
It is used in deflection plates of CRO to sweep the electron beam from left to right. It is also used in TV.
23. Give the expression for displacement error.
(vs – vs’)max Ts
ed = =
Vs 8RC
24. Define sweep speed.
The sweep speed is defined as the rate of change of sweep voltage with respect to time.
25. Give the expression for sweep speed error.
Difference in slope at beginning and end of sweep Ts
es = =
initial value of slope RC
26. Give the expression for transmission error.
Vs’ – Vs Ts
et = =
Vs 2RC
27. Give the expression for sweep speed for exponential charging.
dvs t
= x e-t/RC
dt RC
28. Give the expression for sweep speed for constant current charging.
dvs I
=
dt C
29. Give the expression for relation between transmission error, sweep speed error and displacement error.
1 1
ed = es = et
8 4
30. What is the purpose of compensating network?
A compensating circuit is added to improve the linearity of the Bootstrap and the Miller time base generators.
31. How can you suppress the transformer oscillation?
In order to suppress the transformer oscillation without loading the blocking oscillator during the pulse interval a damping resistor R in series with a diode may be shunted across the transformer. The diode is introduced with such a polarity that it does not conduct during the pulse interval, but does conduct during the overshoot.
32. What is the principle used in bootstrap circuit?
Bootstrap generator provides a very linear output ramp. The amplitude of the ramp can approach the level of the supply voltage. The output ramp amplitude can be made adjustable over a fixed time period by making resistor adjustable.
33. What are the methods used to improve the linearity of the sweep circuits?
a)By generating an impulse b)By improving the linearity of current divider for yoke.c)By linearization of trapezoidal voltage.
34. Write the equation used to determine sweep frequency of a UJT relaxation oscillator. Calculate the frequency with R = 100 KΏ, C = 0.4 µF and intrinsic stand-off ratio 0.57. (DEC 2007)
1
Sweep frequency = = 29.6
2.3RClog10(1/1- η)
35. Draw the equivalent circuit of pulse transformer. (NOV 2011)
36. Which are the two important elements of a blocking oscillator?
1. Active element like transistor 2. A Pulse transformer
37. What is the function of pulse transformer in blocking oscillator?
A pulse transformer is used to couple output of the transistor back to the input. The nature of such feedback through pulse transformer is controlled by relative winding polarities of a pulse transformer.
38. What is leading edge response?
At start there is an overshoot and then the pulse settles down.The response till it settles down after theovershoot is called leading edge response.
39. What is trailing edge response?
The response generally extends below the zero amplitude after the end of pulse width is called back swing. The portion of response from back swing till it settles down is trailing edge response.
40. What is flat top response?
The portion of the response between the trailing edge and the leading edge is called flat top response.
41. What is droop?
The displacement of the pulse amplitude during its flat response is called droop or a tilt.
42. What is the disadvantage of base timing monostable blocking oscillator?
In monostable blocking oscillator, the pulse width is linear function of hFE which is temperature dependent. Also its value changes from transistor to transistor and hence pulse width gets affected due to transistor replacement. This is the biggest disadvantage of the circuit and hence base timing circuit is not used if stable pulse width is required.
43. Which are the two types of astable blocking oscillator?
1.Diode controlled blocking oscillator 2. RC controlled blocking oscillator
44. What is mark space ratio?
The ratio of time for which Q is ON to time for which Q is OFF is called mark space ratio. If this is unity, then the output is almost symmetrical square wave.
45. Define Duty cycle.
The duty cycle is defined as the ratio of the time tp to the time period T. Mathematically it is given by D = tp / T.
46. What do you mean by voltage time base generators?
Circuits used to generate a linear variation of voltage with time are called voltage time base generators.
47. What are the applications of the voltage time base generators?
1. In cathode ray oscilloscope 2.In radar 3.In television indicators 4.In precise time measurements and 5.In time modulation
48. List important sweep parameters.
Important sweep parameters are: sweep speed error, displacement error and transmission error.
49. Name the different errors in generation of sweep waveforms.
Different errors in generation of sweep waveforms are: sweep speed error, displacement error and transmission error.
50. Give the expression for sweep voltage for exponential sweep circuit.
Vs = V (1-e-t/RC)
PART – B
1. Draw the circuit diagram of a monostable transistor blocking oscillator with emitter timing. Explain its operation with the equivalent circuit during the pulse formation. (NOV 2011)
2. Explain the operation of a free running (astable) blocking oscillator. (MAY 2005)
3. With necessary waveforms and circuit diagram explain the method of generating a linear sweep voltage using Bootstrap circuit.(DEC 2008, DEC 2009, JUNE 2009)
4. Define slope, displacement and transmission errors with reference to a sweep signal. (MAY 2005)
5. Define the errors that are used to measure the deviation from linearity of a sweep signal. (MAY 2005)
6. With a neat circuit diagram and relevant waveforms, explain the performance of a triggered transistor blocking oscillator. (MAY 2008)
7. With suitable circuit diagrams, explain the following 1.UJT sawtooth generator 2.Miller sawtooth generator. (MAY 2008, MAY 2010, MAY 2012)
8. A uni-junction transistor with η = .62(intrinsic stand-off ratio) is used in a relaxation oscillator circuit with R = 5 KΏ and C = 0.05 µF. 1.Determine the period and frequency of oscillation 2.Determine the new value of R, which must be changed in order to obtain a frequency of oscillation of 50Hz. 3. If C is increased by a factor of 10, how the value of R changes,if the frequency is to be 50Hz. (DEC 2006)
9. With neat circuit diagram, explain monostable blocking oscillators with base and emitter timing. Draw necessary waveforms.(DEC 2009, MAY 2010, 2011)
10. Describe the working of UJT relaxation oscillator.(DEC 2009, JUN 2010)
11. Draw the circuit diagram and explain the operation of a Push-pull Astable blocking oscillator with emitter timing. (JUN 2010)
12. Explain with circuit diagram and waveforms the voltage time base generator.
13. Draw the circuit of a simple current time base generator. Explain the working of the circuit with associated waveforms. (DEC-2007 & NOV 2010)
14. For a diode controlled astable transistor blocking oscillator circuit with the following parameters L =5.2mH,C=90pF,Vcc=10V,R=500Ώ,Vr=6Vn=1 and VBB=0.5V. Calculate 1. The period and duty cycle 2.Peak voltages and currents 3. Current in magnetizing inductance at the end of one cycle. Neglect saturation junction voltages. (Nov./Dec-2006)
15. Explain the method of triggering the blocking oscillator using transistor. (JUN 2006)
16. Draw the circuit of an astable blocking oscillator with base timing. Sketch the wave forms of collector voltage and magnetizing current. Explain the operation of the oscillator covering one full cycle, along with necessary equations. Sketch the equivalent circuits (1) when there is magnetizing current and (2) when the magnetizing current is zero. Also, mention the advantages and disadvantages of this oscillator. (MAY 2012)
17. For a certain UJT sweep circuit, the resistance is 10 kΩ while the capacitance is 0.1 µF. The valley potential is 1.5V when VBB = 20 V. Assuming diode cutin voltage of 0.7 V and intrinsic stand off ratio as 0.6, calculate the frequency of oscillations. (MAY 2012)
18. Explain bootstrap saw-tooth generator with circuit diagram and draw the output signal. (NOV 2011)
BLOCKING OSCILLATORS AND TIMEBASE GENERATORS
PART –A
1. Define rise time of a pulse. (MAY 2004)
The rise time is an important parameter related to this part of the response. It is defined by the time required by the pulse to rise from 10% of its amplitude to 90% of its amplitude.
2. Define sweep speed error or slope error. (JUN 2006)
It is the ratio of difference in slope at beginning and end of sweep to the initial value of slope.
3. Define displacement error. (JUN 2006&MAY 2011)
It is defined as the maximum difference between the actual sweep voltage and linear sweep which passes through the beginning and end points of the actual sweep.
4. What is UJT relaxation oscillator? (MAY 2010)
A unijunction transistor in conjunction with a capacitor and a charging resistor to construct an oscillator with an approximate ramp type output is known as UJT relaxation oscillator.
5. What is blocking oscillator? Why it is so called? (MAY 2008 , MAY 2010, NOV 2011)
A tuned collector oscillator circuit which uses a regenerative (positive) feedback via a pulse transformer,producing a single pulse or pulse train is called a blocking oscillator. The oscillator cuts itself OFF or BLOCKS after one or more cycles. Hence the name Blocking oscillator.
6. The transistor current sweep circuit will not provide precisely linear sweep. Why? (DEC 2006)
1. Lag of impulse term in current source 2.The inductance of iron core varies with current. 3. The driver transistor which provides the inductor current does not operate with sufficient linearity.
7. What is a pulse transformer? (MAY 2010)
A pulse transformer is basically a transformer, which couples a source of pulses of electrical energy to the load keeping the shape and other properties of pulse unchanged. The voltage level of the pulse can be raised or
lowered by designing the proper turns ratio for the pulse transformer.
8. State the applications of pulse transformer. (MAY 2010, MAY 2012)
Pulse transformer can be used to 1.change the amplitude and impedance level of a pulse 2.invert the polarity of a pulse 3.produce a pulse
in a circuit having negligible dc resistance 4.effect dc isolation between source and load 5.couple between stages of pulse amplifiers 6.differentiate a pulse 7. acts as a coupling element in certain pulse generating circuit.
9. What are the applications of blocking oscillator?(MAY 2008 & MAY 2011)
1. The blocking oscillator can be used as a frequency divider or conter.
2. The blocking oscillator as a low impedance switch can be used to discharge a capacitor quickly.
3. The output of the blocking oscillator can be used as a gating waveform with a very small mark-space ratio.
4.Blocking oscillator is capable of generating a pulse of large peak power. The average power is small since the duty cycle is low.
5. The astable circuit is used as a master oscillator to supply triggers for synchronizing a system of pulse type waveforms-square waves,sweep voltages etc.,
6. The monostable circuit is used to obtain abrupt pulses from a slowly varying
input triggering voltage.
7. Using a tertiary winding, output pulses of either polarity may be obtained
depending upon which end of the winding is grounded. Also, the output winding may be isolated from ground where required.
10. List various sweep circuits. Or What are the various methods of generating a time base waveform? (MAY 2008)
1.Exponential charging circuit 2.Constsnt-current charging circuit 3.Miller circuit 4.Phantastron circuit 5.Bootstrap circuit 6.Inductor circuit 7. Compensating networks.
11. What are current time base generator? (DEC 2005)
Current time base generator are the circuits which produce a current waveform which increases linearly with time. They are used in magnetic deflection system as television displays on large screen tubes and radars.
12. What are the drawbacks of time base generator? How can it be reduced? (DEC 2008)
The main drawback of time base generator is the high percentage slope speed error. It can be reduced by improving the linearity of the sweep by increasing the supply voltage or increasing the time constant of the circuit.
13. Define Restoration time or Flyback time. (JUN 2009, MAY 2012)
The time required for the return for the sweep voltage to the initial value is called the restoration time, the return time or fly back time
.
14. Define sweep time. (DEC 2008, JUN 2009, MAY 2012)
The period during which voltage increases linearly is called sweep time.
15. How can the linearization of trapezoidal voltage can be obtained? Or How is linearization achieved in current time base circuit? (JUN 2010)
It can be obtained by using three different circuit such as bootstrapping, using an op-amp or miller integrator and by changing a capacitor from a common current source such as common base transistor.
16. What is a sweep generator? (MAY 2010)
A sweep generator is a circuit that produces a sweep waveform. Sweep waveforms are those which have at least one portion in it with respect to time. There are different types of sweep generators like Miller time base sweep generator,Bootstrap sweep generator,etc.,
17. What do you mean by free running blocking oscillator?Why they are called so? (JUN 2010)
Astable blocking oscillator is called as free running blocking oscillator.It produces train of pulses when triggered. The pulse width and the duty cycle of the blocking oscillator output can be controlled as per the requirement. There are two types of astable blocking oscillators available:1.Diode controlled astable blocking oscillator 2.RC controlled astable blocking oscillator.
18.Define transmission error. (MAY 2004)
When a ramp voltage is transmitted through a high-pass RC network, its output falls away from the input.The transmission error is defined as the difference between the input and output divided by the input.
19. How will you form an astable blocking oscillator from a monostable blocking oscillator? (DEC 2005)
A diode network can be replaced by RC network to obtain RC controlled astable blocking oscillator. Such RC network can be added either in the emitter circuit of a monostable blocking oscillator or in the base circuit of a monostable blocking oscillator.
20. What do you mean by linear time base generator? (JUN 2007)
A linear time base generator is one that provides an output waveform, a portion of which exhibits a linear variation of voltage or current with time.
21. Compare diode controlled and RC controlled blocking oscillator. (MAY 2008)
Diode controlled blocking oscillator RC controlled blocking oscillator
1.Low duty cycle operation is possible. 1. Low duty cycle operation is impossible
2.Time period and frequency of oscillations can be easily varied by varying R1 or C1 2. Time period and frequency can not be easily varied. To change time period it is necessary to change the entire diode network to alter Vγ value.
3.The oscillations just before the pulse are missing and there is much less possibility of such oscillations. 3.There is possibility of oscillations just before the pulse for low duty cycle operation
4.The design equations are simpler. 4. The equations obtained are complicated and some are transcendental which require graphical solution.
5.The circuit is easy to design. 5. The circuit is difficult to design due to complexity of the equations.
6.The timing values are temperature dependent as diode network is temperature sensitive. 6. The time values does not depend on diode which is temperature sensitive. Hence the timing values are stable and temperature independent provided VBB >>Vγ of transistor and all the elements like R1,C1 etc., are temperature independent.
7. The overshoots after the pulse are absent and hence the waveforms are better and smooth. 7. In low duty cycle operation, voltage across capacitor discharges slowly. Due to this pulse at the collector has distorted waveform.
22. Give the uses of time base generator. (MAY 2011)
It is used in deflection plates of CRO to sweep the electron beam from left to right. It is also used in TV.
23. Give the expression for displacement error.
(vs – vs’)max Ts
ed = =
Vs 8RC
24. Define sweep speed.
The sweep speed is defined as the rate of change of sweep voltage with respect to time.
25. Give the expression for sweep speed error.
Difference in slope at beginning and end of sweep Ts
es = =
initial value of slope RC
26. Give the expression for transmission error.
Vs’ – Vs Ts
et = =
Vs 2RC
27. Give the expression for sweep speed for exponential charging.
dvs t
= x e-t/RC
dt RC
28. Give the expression for sweep speed for constant current charging.
dvs I
=
dt C
29. Give the expression for relation between transmission error, sweep speed error and displacement error.
1 1
ed = es = et
8 4
30. What is the purpose of compensating network?
A compensating circuit is added to improve the linearity of the Bootstrap and the Miller time base generators.
31. How can you suppress the transformer oscillation?
In order to suppress the transformer oscillation without loading the blocking oscillator during the pulse interval a damping resistor R in series with a diode may be shunted across the transformer. The diode is introduced with such a polarity that it does not conduct during the pulse interval, but does conduct during the overshoot.
32. What is the principle used in bootstrap circuit?
Bootstrap generator provides a very linear output ramp. The amplitude of the ramp can approach the level of the supply voltage. The output ramp amplitude can be made adjustable over a fixed time period by making resistor adjustable.
33. What are the methods used to improve the linearity of the sweep circuits?
a)By generating an impulse b)By improving the linearity of current divider for yoke.c)By linearization of trapezoidal voltage.
34. Write the equation used to determine sweep frequency of a UJT relaxation oscillator. Calculate the frequency with R = 100 KΏ, C = 0.4 µF and intrinsic stand-off ratio 0.57. (DEC 2007)
1
Sweep frequency = = 29.6
2.3RClog10(1/1- η)
35. Draw the equivalent circuit of pulse transformer. (NOV 2011)
36. Which are the two important elements of a blocking oscillator?
1. Active element like transistor 2. A Pulse transformer
37. What is the function of pulse transformer in blocking oscillator?
A pulse transformer is used to couple output of the transistor back to the input. The nature of such feedback through pulse transformer is controlled by relative winding polarities of a pulse transformer.
38. What is leading edge response?
At start there is an overshoot and then the pulse settles down.The response till it settles down after theovershoot is called leading edge response.
39. What is trailing edge response?
The response generally extends below the zero amplitude after the end of pulse width is called back swing. The portion of response from back swing till it settles down is trailing edge response.
40. What is flat top response?
The portion of the response between the trailing edge and the leading edge is called flat top response.
41. What is droop?
The displacement of the pulse amplitude during its flat response is called droop or a tilt.
42. What is the disadvantage of base timing monostable blocking oscillator?
In monostable blocking oscillator, the pulse width is linear function of hFE which is temperature dependent. Also its value changes from transistor to transistor and hence pulse width gets affected due to transistor replacement. This is the biggest disadvantage of the circuit and hence base timing circuit is not used if stable pulse width is required.
43. Which are the two types of astable blocking oscillator?
1.Diode controlled blocking oscillator 2. RC controlled blocking oscillator
44. What is mark space ratio?
The ratio of time for which Q is ON to time for which Q is OFF is called mark space ratio. If this is unity, then the output is almost symmetrical square wave.
45. Define Duty cycle.
The duty cycle is defined as the ratio of the time tp to the time period T. Mathematically it is given by D = tp / T.
46. What do you mean by voltage time base generators?
Circuits used to generate a linear variation of voltage with time are called voltage time base generators.
47. What are the applications of the voltage time base generators?
1. In cathode ray oscilloscope 2.In radar 3.In television indicators 4.In precise time measurements and 5.In time modulation
48. List important sweep parameters.
Important sweep parameters are: sweep speed error, displacement error and transmission error.
49. Name the different errors in generation of sweep waveforms.
Different errors in generation of sweep waveforms are: sweep speed error, displacement error and transmission error.
50. Give the expression for sweep voltage for exponential sweep circuit.
Vs = V (1-e-t/RC)
PART – B
1. Draw the circuit diagram of a monostable transistor blocking oscillator with emitter timing. Explain its operation with the equivalent circuit during the pulse formation. (NOV 2011)
2. Explain the operation of a free running (astable) blocking oscillator. (MAY 2005)
3. With necessary waveforms and circuit diagram explain the method of generating a linear sweep voltage using Bootstrap circuit.(DEC 2008, DEC 2009, JUNE 2009)
4. Define slope, displacement and transmission errors with reference to a sweep signal. (MAY 2005)
5. Define the errors that are used to measure the deviation from linearity of a sweep signal. (MAY 2005)
6. With a neat circuit diagram and relevant waveforms, explain the performance of a triggered transistor blocking oscillator. (MAY 2008)
7. With suitable circuit diagrams, explain the following 1.UJT sawtooth generator 2.Miller sawtooth generator. (MAY 2008, MAY 2010, MAY 2012)
8. A uni-junction transistor with η = .62(intrinsic stand-off ratio) is used in a relaxation oscillator circuit with R = 5 KΏ and C = 0.05 µF. 1.Determine the period and frequency of oscillation 2.Determine the new value of R, which must be changed in order to obtain a frequency of oscillation of 50Hz. 3. If C is increased by a factor of 10, how the value of R changes,if the frequency is to be 50Hz. (DEC 2006)
9. With neat circuit diagram, explain monostable blocking oscillators with base and emitter timing. Draw necessary waveforms.(DEC 2009, MAY 2010, 2011)
10. Describe the working of UJT relaxation oscillator.(DEC 2009, JUN 2010)
11. Draw the circuit diagram and explain the operation of a Push-pull Astable blocking oscillator with emitter timing. (JUN 2010)
12. Explain with circuit diagram and waveforms the voltage time base generator.
13. Draw the circuit of a simple current time base generator. Explain the working of the circuit with associated waveforms. (DEC-2007 & NOV 2010)
14. For a diode controlled astable transistor blocking oscillator circuit with the following parameters L =5.2mH,C=90pF,Vcc=10V,R=500Ώ,Vr=6Vn=1 and VBB=0.5V. Calculate 1. The period and duty cycle 2.Peak voltages and currents 3. Current in magnetizing inductance at the end of one cycle. Neglect saturation junction voltages. (Nov./Dec-2006)
15. Explain the method of triggering the blocking oscillator using transistor. (JUN 2006)
16. Draw the circuit of an astable blocking oscillator with base timing. Sketch the wave forms of collector voltage and magnetizing current. Explain the operation of the oscillator covering one full cycle, along with necessary equations. Sketch the equivalent circuits (1) when there is magnetizing current and (2) when the magnetizing current is zero. Also, mention the advantages and disadvantages of this oscillator. (MAY 2012)
17. For a certain UJT sweep circuit, the resistance is 10 kΩ while the capacitance is 0.1 µF. The valley potential is 1.5V when VBB = 20 V. Assuming diode cutin voltage of 0.7 V and intrinsic stand off ratio as 0.6, calculate the frequency of oscillations. (MAY 2012)
18. Explain bootstrap saw-tooth generator with circuit diagram and draw the output signal. (NOV 2011)
very good type of question answers
ReplyDeletemore specific questions are also erected such as troubleshooting of blocking oscillator ,
use of switching components , selection of circuits for specific applications
For well define answer question shall not start with 'Wh '