EE 321 Diodes I Fall 2003EE321Diodes, Part 1 — The I-V Characteristics of DiodesThe purpose of this lab is to investigate the i-v (current-voltage) characteristics of rectifier andzener diodes.Rectifier Diodes1. Use the circuit in Figure 1 to display the i-v characteristic of the 1N4001 rectifier diode onyour scope using its X-Y capability. This is very similar to the method we used to measure thetransfer function in Lab 1. Note that in Figure 1 the ground of the oscilloscope is not the sameas the ground of the circuit. Many instruments receive their ground reference through thepower cord, including our sc ope, power supply, and signal generator, to prevent potentiallydangerous shocks. By using the isolation transformer between the function generator and thewall power you may break this reference and set a new reference by the output connections.1N4001FloatingFunctionGenerator100Ch 1Ch 2Scope GroundΩFigure 1.Check the 1N4001 datasheet. What is the maximum forward current and maximum reversevoltage the diode can handle? Can your function generate exceed these values?Change your scope inputs/settings to obtain a ‘normal-looking’ i-v characteristic (e.g. Sedraand Smith p. 132). Vary the amplitude of the signal generator and observe the X-Y trace.At what voltage (within 0.1 V) does the diode appear to ‘turn on’ (current starts to flow)?2. Sketch the i-v curve. Be sure your amplitude is large enough so the current reaches atleast 20 mA. Label axes and add voltage and current scales. Determine the forward voltagewhen the current is 1 mA and 10 mA (use the time mode and cursors). Does the forwardcharacteristic remain exponential up to the m aximum forward current? (Can you tell?)3. Remove the diode from the circuit and use the diode setting of your multi-meter to check thediode. In this setting the multi-meter puts 1 mA into your diode and measures the voltage.How does this c ompare to your result from Part 2?Zener Diodes4. Using the setup of Figure 1 display and sketch the i-v characteristics for the 1N5229 and1N5237 zener diodes. For each diode, measure the zener voltage at a reverse current of20 mA and compare with the specification values from the datasheet. Which diode has thesteeper slope in the breakdown region? Which would make a better voltage regulator?1EE 321 Diodes I Fall 20031N4001About+10VRFigure 2.5. Each of the zener diodes has a 500 mW power rating. What maximum steady zener currentdoes this imply?Diode Forward Characteristics6. Compute the parameters n and ISwhich govern the forward diode characteristic by measuringIDand VDat two points in the forward bias region of your 1N4001 diode. Use the circuitshown in Figure 2 (do not use the function generator or scope this time). Make measurementsusing a 1 KΩ (to give ID= 10 mA) and then a 10 KΩ (to give ID= 1 mA) current limitingresistor. Adjust the 15 V power until the voltage accross the resistor is 10 V, and measure thediode voltage. (Do this accurately using a digital multi-meter to measure the voltage acrossthe current-limiting resistor.) Sketch circuit and show calculations for n and IS(Ref: Sedraand Smith p. 132-134).Compare the 1 mA voltages of parts 2, 3 and 6. If the difference is more than 20% repeatand carefully check each measurements.7. Measure the incremental resistance rdof the above diode at DC bias current ID= 1 mA (seefigure 3.25 in Sedra and Smith). Use the circuit in Figure 3 and your oscilloscope. (Thefloating signal generator provides a ”small signal” vd, idaround the bias point set by the dcpower supply. Observe the small signals using AC coupling on the scope.) The incrementalresistance is given by rd= vd/id. Compare your measurements with the theoretical value forrd(Eq 3.53 in Sedra and Smith).1N4001FloatingFunctionGeneratorScope GroundCh 2Ch 1About+10V10k ΩFigure 3.2EE 321 Diodes I Fall 2003Pre-Lab1. Use the diode equation (eq 3.1 in Sedra and Smith) to find the expected iDfor vD= 0.1, 0.2,0.3, 0.4, 0.5, 0.6, 0.7 and 0.8 V (let IS= 30 × 10−8A and n = 2).2. If you had measured the diode current iD= 1 mA at vD= 0.6 V and iD= 10 mA atvD= 0.7 V, find ISand n for that