Bootstrap Sweep Circuit
PreLab:
 Study the operation and working principle of Bootstrap Sweep Circuit.
 Study the procedure for conducting the experiment in the lab.
Objectives:
 To design a Bootstrap Sweep Circuit.
 To obtain a sweep wave form.
Components Required:
 Resistors – 100kohms , 5.6kohms, 10 Kohms  1 each
 Capacitors – 0.1microF, 10microF, 100microF  1 each
 IN4007 Diode – 1 No.
 2N2369 Transistors – 2 Nos.
 Bread Board
Apparatus Required:
 Power supply (0V30V)
 CRO(1Hz20MHz)
 Signal generator (1Hz1MHZ)
 Connecting Wires.
Circuit Diagram:
Theory:
The input to Q_{1} is the gating waveform. Before the application of the gating waveform, at t = 0, transistor Q_{1} is in saturation. The voltage across the capacitor C and at the base of Q_{2} is V_{CE(sat)}. To ensure Q_{1} to be in saturation for t = 0, it is necessary that its current be at least equal to I_{CE} / h_{FE} so that R_{b} < h_{fe}R.
With the application of the gating waveform at t = 0, Q_{1} is driven OFF. The current I_{C1} now flow into C and assuming unity gain in the emitter follower V_{0}. When the sweep starts, the diode is reverse biased, as already explained above, the current through R is supplied by C_{1}. The current V_{CC} / R through C and R now flows from base to emitter of Q_{2}.if the output V_{0} reaches the voltage V_{CC} in a time T_{S} / Tg, then from above we have T_{S} = RC.
Procedure:
 Connect the circuit as shown in figure.
 Apply the square wave or rectangular wave form at the input terminals.
 Connect the CRO at output terminals now plug the power card into line switch on and observe the power indication.
 As mentioned in circuit practical calculation. Observe and record the output waveforms from CRO and compare with theoretical values.
Expected Waveforms:
Inference: Conclusions can be made on sweep time T_{S} and retrace time T_{R} and sweep voltage V_{S} of the sweep waveform theoretically and practically and also made on if the output waveform of the Bootstrap are identical with the theoretical wave forms or not.
Viva Questions:
1. Define (a) Voltage time base generator, (b) current time base generator (c) linear time base generator.
Ans:
 A voltage timebase generator is one that provides an output voltage waveform, a portion of which exhibits a linear variation with time.
 A current timebase generator is one that provides an output current wave form, a portion of which exhibits a linear variation with time.
 A linear timebase generator is one that provides an output waveform a portion of which exhibits a linear variation of voltage or current with time.
2. What is the relation between the slope error, displacement error and transmission error?
Ans: The relation between slope, displacement and transmission is given as es = 2et = 8ed.
3. What are the various methods of generating time base waveform?
Ans: The methods of generating a timebase waveform are exponential charging, constant current charging, the miller circuit, the phantastron circuit, the bootstrap circuit, compensating networks, an inductor circuit.
4. Which amplifier is used in Bootstrap time base generator?
Ans: In bootstrap timebase generator, a non inverting amplifier with unity gain is required.
5. Which type of sweep does a bootstrap timebase generator produce?
Ans: A bootstrap timebase generator produces a positivegoing sweep.
6. What is the gain of the amplifier used in Bootstrap time base generator?
Ans: In bootstrap timebase generator, a non inverting amplifier with unity gain is required.
7. What is retrace time? Write the formula for the same for Bootstrap time base generator.
Ans: The time taken by signal to return to its initial value is called retrace time. The retrace time is given by Tr = (CV_{S} / V_{CC})/(h_{FE}/R_{B})  (1/R).
8. What is the formula for sweep amplitude in Bootstrap time base generator?
Ans: The formula for sweep amplitude in bootstrap time base generator is given as V_{S} = V_{CC}Tg / RC.
9. To have less flatness time of sweep signal, then the gate signal time has to be __.
Ans: To have less flatness time of sweep signal, then gate signal(Tg) has to be equivalent to sweep time (Ts).
10. A Bootstrap sweep circuit employs __ type of feedback.
Ans: A bootstrap sweep circuit employs positive feedback.
Design problem:
 Design Bootstrap Sweep Circuit with sweep amplitude of 8V, with sweep interval of 1ms neglect flyback time and e_{s }= 0.25.
 Design Bootstrap Sweep Circuit with sweep amplitude of 15V, with sweep interval of 2ms neglect flyback time and e_{s} = 0.1.
Outcomes: After finishing this experiment students are able to Design Bootstrap sweep circuit and able to generate a sweep voltage waveform.

UpdatedMar 05, 2020

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