Bootstrap Sweep Circuit

Pre-Lab:

  1. Study the operation and working principle of Boot-strap Sweep Circuit.
  2. Study the procedure for conducting the experiment in the lab.

Objectives:

  1. To design a Boot-strap Sweep Circuit.
  2. To obtain a sweep wave form.

Components Required:

  1. Resistors – 100kohms , 5.6kohms, 10 Kohms  - 1 each
  2. Capacitors – 0.1microF, 10microF, 100microF  - 1 each
  3. IN4007 Diode – 1 No.
  4. 2N2369 Transistors – 2 Nos.
  5. Bread Board

Apparatus Required:

  1. Power supply (0V-30V)
  2. CRO(1Hz-20MHz)
  3. Signal generator (1Hz-1MHZ)
  4. Connecting Wires.

Circuit Diagram:

Theory:

The input to Q1 is the gating waveform. Before the application of the gating waveform, at t = 0, transistor Q1 is in saturation. The voltage across the capacitor C and at the base of Q2 is VCE(sat). To ensure Q1 to be in saturation for t = 0, it is necessary that its current be at least equal to ICE / hFE so that Rb < hfeR.

With the application of the gating waveform at t = 0, Q1 is driven OFF. The current IC1 now flow into C and assuming unity gain in the emitter follower V0. When the sweep starts, the diode is reverse biased, as already explained above, the current through R is supplied by C1. The current VCC / R through C and R now flows from base to emitter of Q2.if the output V0 reaches the voltage VCC in a time TS / Tg, then from above we have TS = 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 TS and retrace time TR and sweep voltage VS 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:

  1. A voltage time-base generator is one that provides an output voltage waveform, a portion of which exhibits a linear variation with time.
  2. A current time-base generator is one that provides an output current wave form, a portion of which exhibits a linear variation with time.
  3. 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.

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 wave-form?

Ans: The methods of generating a time-base 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 Boot-strap time base generator?

Ans: In bootstrap time-base generator, a non inverting amplifier with unity gain is required.

5. Which type of sweep does a bootstrap time-base generator produce?

Ans: A bootstrap time-base generator produces a positive-going sweep.

6. What is the gain of the amplifier used in Bootstrap time base generator?

Ans: In bootstrap time-base 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 = (CVS / VCC)/(hFE/RB) - (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 VS = VCCTg / 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:

  1. Design Boot-strap Sweep Circuit with sweep amplitude of 8V, with sweep interval of 1ms neglect flyback time and e= 0.25.
  2. Design Boot-strap Sweep Circuit with sweep amplitude of 15V, with sweep interval of 2ms neglect flyback time and es = 0.1.

Outcomes: After finishing this experiment students are able to Design Boot-strap sweep circuit and able to generate a sweep voltage waveform.

  • Created
    Dec 09, 2015
  • Updated
    Mar 05, 2020
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    26,712