Experiment 3 The Curve Tracer W Oldham W T Yeung R Lu and R T Howe UC Berkeley EE 105 Fall 2003 1 0 Objectives The purposes are twofold 1 Familiarity and competency in use of the HP now Agilent Technologies 4155A or 4155B as curve tracers and 2 thorough understanding of I V curves for linear and non linear electronic devices 2 0 Prelab Read the HP 4155A B instrument manual pages 4 10 4 39 and 3 70 3 77 appended to the end of this experiment and answer these questions Q1 Review the primer on basic circuit analysis see Appendix in lab manual Carefully sketch the I V characteristics of the following circuits Use 10 mA full scale with 1mA ticks for the ordinate and 10 V full scale with 1 V ticks for the abscissa 2K 67 K a I 4K V 1 5 V 1K I b V 1 Prelab Q2 Sketch the parametric I V graph of the following circuits 10 mA 10 V full scale with the control electrode G set at 0 1 2 3 4 5 V We want I D y axis plotted versus V DS x axis with V GS as a parameter See the Supplementary Notes to this lab for help on the relay control G 10 K a ID S D 1K 1K G Relay switch Relay control 1K b D 1K ID S V Need 100 mA compliance on I G Q3 The canned FET V DS I D program controls the SMU s in the following way Sketch the connections you would use to accomplish the measurement described in Q2a Which SMU would you use for which terminal S G or D and indicate which SMU current and voltage are to be plotted for the I D vs V DS curve V1 0 I1 SMU1 V1 V 1 vs time 0 V2 I2 SMU2 V2 V 2 vs time 0 I3 V3 2 t t V3 SMU3 V 3 vs time 0 Experiment 3 The Curve Tracer t Procedure is the symbol for an ammeter and Note V is the symbol for a voltage source 3 0 Procedure 3 1 HP 4155A B Setup and Use 1 Using the front panel create a program to generate 2 terminal I V characteristics with 10 mA 10 V full scale Start with the canned diode program 2 Generate the I V curve for the prelab circuits 1a and 1b Print the graphs 3 Input a program for the 3 terminal parametric I V measurement described in prelab Question 2a and 2b 4 Generate the I V curve for the prelab circuits 2a and 2b Print the graph You can start with the canned F S ET I DS vs V DS program 5 Save your program on your floppy 3 2 Diode I V Characteristics 1 Take the 4 quadrant I V characteristics of a simple silicon diode using the same scale as in 3 1 1 Print the curves Use a pencil to draw a straight line approximation 2 straight lines to approximate the entire 4 quadrant graph 2 Take the log I vs linear V characteristics of the diode in the forward biased quadrant i e for V polarity which causes current flow Cover the range I 10 9 A to 10 1 A Print the plot hint you can make a simple modification to your program to do this 4 0 Appendix General Overview of HP 4155A B 1 Introduction These instruments are general purpose parameter analyzers that is instruments that can extract plot and analyze the terminal characteristics of devices and circuits In this course we will introduce them and largely use them as simple curve tracers that is tools to display the I vs V behavior of devices and simple circuits containing devices If you are not completely familiar with the concept of characterizing a box by its terminal I V characteristics please review the first appendix to the lab manual Experiment 3 The Curve Tracer 3 Appendix General Overview of HP 4155A B 2 Principle of Operation The HP 4155A B instruments are far more powerful than we need just as your computer spreadsheet program is much more powerful than 99 of user requirements For example on these instruments there are 4 independent drive sense nodes called SMUs connection points where the instrument will be happy to apply any potential you desire and monitor the current or alternatively apply a current and monitor the potential 2 voltage source nodes VSUs voltage monitor nodes VMUs as well as some other programmable nodes we don t need to talk about We will generally use only the three SMUs in this lab 4 Built in or Canned Programs You will find some especially useful built programs that do almost 100 of the work for you and eliminate the need to take a 3 unit course on the instrument before using it There is a two terminal I V plotter program and two three terminal programs equally useful The FET program plots I vs V at one terminal while stepping the voltage at the third Similarly the BJT program plots I vs V at one terminal while stepping the current at a third 5 Detailed Information on Operating the 4155 5 1 What compliance means What is the instrument to do if you provide a very low resistance circuit and ask it to ramp a voltage say up to 10 V Self destructing is not an option needless to say You will probably not be happy if your device starts smoking either To deal with this question the user gets to set something called compliance which is a specification of a maximum parameter value In part 3 1 1 above suppose you intended only to look at currents in the 0 10 mA range You would set the compliance of SMU2 to 10mA and the voltage sweep would stop when that current is reached A major purpose of the compliance setting is to limit power dissipation in your device under test The average small device cannot dissipate more than 50 100 mW without risking burn out So if you are sweeping voltage say over a range of 0 10 V you might want to limit current to 5 mA and so forth 5 2 How relay switches operate A generic schematic for a relay switch is provided in the following figure The device has four electrical terminals two are connected across the switch and two are connected to the electromagnet which controls the position of the electrical switch When the applied voltage across the electromagnet exceeds a threshold value which assume to be 2 5 V for this example the electrical switch closes and pins 8 and 4 are shorted If the electromagnet voltage vG drops below the threshold the switch opens pins 6 and 4 are shorted The switch operation is illustrated by the plot of switch position versus electromagnet voltage 4 Experiment 3 The Curve Tracer Appendix General Overview of HP 4155A B switch position 6 16 8 electromagnet 4 1 relay switch electrical switch off state 2 5 V vG The schematic …
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