MASSACHUSETTS INSTITUTE OF TECHNOLOGY 6 071 Introduction to Electronics Signals and Measurement Spring 2006 Laboratory 17 Diodes Signal conditioning Voltage regulation Voltage Regulator The Zener diode with its well defined breakdown voltage may be used for building a very effective voltage regulator In this exercise we will construct and test a voltage regulator circuit 2 Rs 1 supply D unregulated 3 3 V Vs Vz RL voltage The supply is able to provide a maximum current of 1 5A and the Zener diode has an effective resistance of 30 Using Rs 500 and RL 10k build the above circuit From the class web site download the instrument called ZenerRegulator This instrument controls the variable power supply of your ELVIS unit Make the following connections to your protoboard Node 1 Connected to ACH1 measures the unregulated voltage Vs Node 2 Connected to ACH2 measures the regulated voltage Vz Run your instrument and observe the response of the circuit regulated voltage Vz as the unregulated voltage Vs is varied Try adding noise to Vs and observe Vz Note the loading effect of this voltage regulator circuit As Vs gets larger what is the max Vz across the load Given the maximum Vz and the diode s effective resistance calculate the maximum current through the diode Iz What is the maximum current Is 22 071 6 071 Spring 2006 Chaniotakis Cory Page1 Voltage Level Protection The signal V1 generated by circuit 1 is transmitted to circuit 2 for further processing However circuit 2 is very sensitive to voltage excursions above a certain level In this example this voltage level is 6 6 Volts The signal generated by circuit 1 is expected to be less than 6 6 Volts but it has been observed that certain transients that were not taken into consideration in the original design of circuit 1 may create voltage spikes greater than 6 6 Volts These voltage spikes destroy circuit 2 and that is bad We would like to modify the circuit arrangement shown below so that the voltage seen by circuit 2 is always clamped at 6 6 Volts Show your solution V1 circuit 1 22 071 6 071 Spring 2006 Chaniotakis Cory V2 circuit 2 Page2 Peak Finder and Keeper Circuit The rectifier circuit studied in the previous lab consisted of a diode in series with a resistor as shown below R4 10k Vs Vo Now by incorporating an energy storage element the capacitor C3 in the circuit below the behavior of the circuit is modified in a very useful way Vs C3 0 1uF R4 10k Vo For this exercise let s construct and test the circuit above For Vs use the function generator and observe the input and output signals of your circuit with the oscilloscope How are the amplitudes of Vs and Vo related What is the characteristic time c of this circuit c is the time it takes for a signal to fall to 1 e of it s peak value or grow to 1 1 e of it s peak value In this case determine how the voltage Vo across C3 decays as the capacitor dissipates power in R4 when Vs is negative and the diode is off Provide a signal Vs from your function generator and observe the output as a function of the frequency In the space provided below draw the superimposed signals Vs and Vo for a the following frequencies 5Hz 50Hz and 1kHz 22 071 6 071 Spring 2006 Chaniotakis Cory Page3 LED Voltage Level Indicator Consider the following circuit R Vz I Vs Vo This circuit is constructed with a Zener diode an LED a resistor and a voltage source Calculate the minimum voltage Vs that will turn the LED on Assume that the forward voltage of the LED is Vg Build the circuit with a 3 3 Volt Zener diode Determine the value of R required to limit the current through the diodes to 10 mA For Vs start a triangular wave signal with a frequency 5 Hz varying from 0 to 5 Volts Observe the output voltage Vo Increase the frequency of Vs and determine the highest frequency that you can observe the blinking of the LED 22 071 6 071 Spring 2006 Chaniotakis Cory Page4
View Full Document
Unlocking...