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ECEN Experimental Method III

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					          ECEN 3314 Electronic Devices and Applications
                                           Fall 2007
                      Lab. 2 Diode and Rectifier Circuits
1. Objective ( One Week Lab)
To investigate I-V curve of diodes, switching characteristics, DC/AC circuits, the full
wave rectifier circuit, doubler, and other applications of diode circuits.
2. Components Required
1N4007 rectifier diodes, 1N4148 switching diode, 1N5231 5.1V Zener diode, resistors
and capacitors, all of the parts used in this lab are included in the lab kit. The data
sheets of the parts can be found at: http://www.datasheetcatalog.com/
3. Equipment Required
Curve tracer, dual dc source , oscilloscope, function generator, digital multimeter. Op
amp/diode PCB.
4. Topics
   1)   Learn to use curve tracer or Instrumentation amp to observe diode I-V curves.
   2)   Study the current/voltage on a Zener diode behavior.
   3)   Voltage limiters.
   4)   Peak rectifiers.
   5)   DC power supply.

5. Prelaboratory
   1) Review OrCAD/PSPICE simulation tool.
   2) Review Chapter 3 of Microelectronic Circuits, 5th edition, the textbook of ECEN
      3314.
                         V= 0.2
                        to 0.7V
                                                  P                   “Free
                                                            +         node”
                                                                                     V= .7V
                                                                                      to




                        P         N                   V=0
                                          Vo(t)
                                                                                         0.2
                                                                                         0




                                                            -
                                                                       V= 0.2
              Vi(t)                   R                                to 0.7V
                                                                                     N

                                                                                 R



                            (a)                                 (b)

                                              Figure 1




                                                  1
When the diode is turned on, there is a finite voltage drop, for silicon pn junction diode,
this value is takes on a voltage value ranging from 0.2 to 0.7 V as current is varied.
Sometimes an ideal diode without such offset is required, and such a device can be
constructed with the combination of an Op-Amp and an ordinary diode. The circuit
shown in Figure 1(a) is a simple rectifier circuit, and is often referred to as a “super
diode” it can be constructed as in Figure 1(b). If the amplitude of the sine wave is
0.5V, suggest what’s the difference in the output when an ordinary diode and the
super diode is inserted into the circuit. Why might one call it super diode?

   3) Estimate/determine the values of the resistor R in the following circuit, such that
      the current is 250 A, 2.5 mA and 25 mA (assuming a 5 V Zener diode). Refine
      your design with simulation and verify experimentally for a 2.5 mA current
      observe and record all voltage drops and current. Your results will also be used
      in the limiter circuit of Figure 2 (b) to set a 2.5 mA current at 10 Vpp.
                                                  R



                            10Vdc                 D1N5231




                                             Figure 2

   4) Simulate the voltage limiter (double sided) circuit of Figure 3 a) with the Zener
      diode and switching diode, 1N4148 in parallel and verify experimentally.

   5) Characterize the I-V properties of both the Zener diode, 1N5231 and pn junction
      switching diode, 1N4148 experimentally with the curve tracer – SIMULATION IS
      NOT REQURED. Refer to Figures 2 and 3(b). In the reverse mode record 10
      data points in the forward mode record 5 points per decade of current change.

                R                                                R


                                     vo(t)
        vs(t)             D1         D2                  vs(t)         D1         D2 vo(t)




                          (a)                                               (b)


                                              Figure 3


                                              2
  6) Simulate the peak rectifier circuit with a filter capacitor of 47 F, the input is a
     sine wave with frequency of 150 Hz and amplitude of 3 V. Select a load resistor
     of 150. Very the input frequency from 50 to 500Hz and observer and record
     the output wave forms (50, 150, and 500Hz). Why do the output waveforms
     look different when the frequency is changed?




                                    Vs(t)                           C                      R             Vo(t)




                                                  Figure 4 Peak rectifier circuit.




                                                                               VDD   PP
         PP
        PP        PP EX3 PP        PP
                                  PP                                         PP       PP        PP
                                             PP    PP    PP                                                PP
        PP
       PP         PP EX2 PP       PP
                                  PP                                PP       PP                                                          PP
                                                                                                                                         PP
                                         PP
                                          PP        PP
                                                   PP
                     PP                                   PP                               R2                        RF             CF
                                                                     R1                              1     14
                                             PP           PP                                         2     13                                      PP
                          R




                                                   PP
              5




                              6
              R




                                                               PP PP                                 3     12
                                                                          RI                                                   RI
       PP                          PP                                     RI
                                                                                                     4     11                                 RF
                                                               PP PP                                 5     10             NC
                              5
              R




                                                          PP                                         6      9             NC
                          R
              6




                                                                                                                                    CF
                     PP                                                 R1                R2         7      8             NC
                                                          PP
                                         PP        PP
                                                  PP
                                             PP                     PP       PP
                                                                             PP                                 PP
                                                                                                                PP        PP
                  PP EX1 PP        PP
                                  PP
        PP
       PP
                                             PP PP       PP
                                                                                                 VSS
                          PP      PP    PP                     PP   PP       PP      PP
                                                                                     PP    PP              PP        PP    PP


        PP: Probe Point                                        CF: Feed back capacitance for
        EX: Extra Probe points                                      differential amplifier
        R1, R2: Feed back resistances                          RF: Feed back resistance for
        RI: Input resistance                                       differential amplifier

       Note: Probe pads with same colour need to be externally connected.
       NC: No connection


                                  Figure 4 PCB setup for diode experiments.

6. Laboratory Work
  1) Implement the circuits of Figures 2, 3, and 4. Observe and recoded currents,
     voltages and transient waveforms (Figures 2 & 3).
  2) Measure the current-voltage relationship of a switching/rectifying and Zener
     diodes with the curve tracer.       Flip the Zener diode polarity reversing


                                                                     3
     configuration, and observe the change. When the Zener diode is put in the
     same polarity with the switching diode, what can you observe? Record and
     plot the IV characteristic for both the PN switching diode and the Zener diode.
  3) Investigate the current-voltage relationship of a Zener diode with a DC circuit
     (Figure 2). Put in resistor designed in the pre -lab and measure the voltage drop
     across the diode such that the current is approximately 2.5 mA. Adjust the
     voltage in 3 steps from 5.5V, to 10V to 15V (you might not able to get the
     exact resistor value derived from the simulation; instead, you can use a
     resistor with the closest value). Record the current, zener voltage, and
     resistor drop at 5.5V, to 10V to 15V respectively. How stable is the zener
     voltage? How do you model this?
  4) Design and implement a voltage limiter circuit using your Zener diode, such that
     the amplitude of the output is limited to approximately +5V/-.7V, assuming the
     input signal is a sine wave with 10Vpp. If you use too smaller a resistor (no
     less than 100  ) what will happen? Assume you zener diode can safely
     dissipate 200mW. Is D2 necessary in Figure 3(a).
  7) Construct the peak rectifier circuit with a filter capacitor of 47 F, the input
     voltage is a sine wave with frequency of 150 Hz and amplitude of 3 V. Select a
     load resistor of 150. Very the input frequency from 50 to 500Hz and observer
     and record the output wave forms (50, 150, and 500Hz). Why do the output
     waveforms look different when the frequency is changed? In each case
     how does the time constant of the peak rectifier load compare to the period
     of the applied sine wave voltage.


7. Laboratory Report
  1) Provide the schematics of your circuit with all components clearly
  indicated(Prelab).
  2) Present your result with tables, transient waves forms, curves etc. (empty data
  tables for prelab.
  3) Record and explain any departures from predicted phenomena.
  4) Attach the key simulation results (embedded into the text along with the data and
  discussion is better).
  5) Attach the important experimental results (embedded into the text as part of the
      discussion again is better).

  6) Discuss the questions highlighted through the body of the text of the experiment.




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