EEEE 480 Analog Electronics

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1 EEEE 480 Analog Electronic Lab #1: Diode Characteritic and Rectifier Circuit Overview The objective of thi lab are: (1) to extract diode model parameter by meaurement of the diode current v. voltage characteritic; (2) to imulate half-wave rectifier circuit; and (3) to evaluate the performance of a half-wave rectifier. Theory Parameter Extraction The current id in a diode i related to the voltage vd acro it by qv D / nkt i I e 1 eq. 1 D S Where IS = revere aturation current (that i, the current that flow through the diode when it i revere biaed, but not in breakdown) q = magnitude of the charge on an electron (= 1.6 x Coulomb) n = a non-ideality factor that range in value between 1 and 2; ideally, n = 1 k = Boltzmann' contant (= 1.38 x J/K) T = abolute temperature (K). The trongly aymmetric nature of the diode behavior hould be noted. When vd > 0 (i.e., under forward bia), the current rie exponentially with applied voltage and ignificant amount of current can flow. On the other hand, when vd < 0 (i.e., under revere bia), current i limited to the revere aturation current IS, which i typically in the picoamp to nanoamp range. It i a trong function of temperature. (Under revere bia the electric field in the pace charge layer can exceed breakdown, typically 3E5 V/cm for ilicon, reulting in ignificant revere current. Some diode, known a Zener diode, are deigned pecifically to be ued in breakdown mode.) A ueful approximation i that when vd > 0, the exponential term in the diode equation can be conidered to be ignificantly greater than 1, and the diode equation can be written a: i D I S e qv D / nkt By obtaining an appropriate plot of id a a function of vd from a circuit uch a that hown in Figure 1, it i poible to extract the parameter n and the revere aturation current IS.

2 R = 330 i D v v D Figure 1. Circuit for meaurement of diode characteritic Half-Wave Rectifier If the diode in the rectifier circuit hown in Figure 2 i ideal, then it will act a a hort circuit when v(t) > 0 and a an open circuit when v(t) < 0. The output voltage will conit only of the poitive half cycle of the input. The expreion for the output are v t when v t 0 v t o 0 wh en v t 0 (Ideal) v (t) ~ R L 1 k v o(t) Figure 2. Half-wave rectifier circuit with ideal diode If the diode in the circuit i not ideal, then it can be modeled by a erie equivalent circuit hown in Figure 3. The ideal diode component reflect the rectifying nature of the circuit and, a before, ha no voltage drop acro it when it i on (forward-biaed). The output i then given by v o t R L R r L 0 D v t V when v t D 0 when v t V V D 0 D 0 Where V D0 i the built in voltage ~ 0.7 V D0 r D (Ideal) v (t) ~ R L 1 k v o(t) Figure 3. Half-wave rectifier circuit with non-ideal diode behavior Analog Electronic EEEE 480 Lab #1: Diode Characteritic and Rectifier Circuit Rev2019v1 Page 2 of 7 Rocheter Intitute of Technology

3 There will be a certain interval in each cycle when the output i zero. Thi correpond to time interval when v t V D. 0 Two meaure can be ued to characterize the rectifier performance the conduction ratio and the peak offet, defined a follow: Conduction ratio Conduction Period of time the of input the diode ignal Peak offet (Peak value of v(t) peak value of vo(t)). where the conduction time i the time that the diode i on and conducting current during one cycle of the input ignal. For an ideal diode in the half-wave rectifier circuit, the conduction ratio would be 0.5 and the peak offet would be 0. The output voltage from the circuit of Figure 2 and 3 will be highly variable over time, approximately duplicating the input voltage when it wing high, and remaining at zero when the input wing low. Although thi contitute a DC voltage in the very limited ene of having a non-zero average value, it i clearly not true DC, which i invariant over time. A firt tep toward producing true DC i hown in Figure 4, in which a capacitor i added in parallel to the load RL. The reulting output ignal will till vary omewhat with time, but ignificantly le than the output from Figure 2 or 3 ince the capacitor attempt to hold the output voltage. During the half cycle when the diode i conducting, the capacitor charge; when the diode i off, the capacitor dicharge through RL. The difference between the maximum and the minimum output voltage i known a the ripple voltage. Ideally, the ripple voltage, Vr, would be 0. Practically, the larger the capacitor, the maller the ripple voltage. Irrepective of the pecific amount of ripple voltage, however, the reulting output ignal i ignificantly cloer to true DC than the output without the capacitor in place. v (t) ~ R L 1 k C L 10 F v o(t) Figure 4. Half-wave rectifier circuit with capacitor to limit output voltage variation Analog Electronic EEEE 480 Lab #1: Diode Characteritic and Rectifier Circuit Rev2019v1 Page 3 of 7 Rocheter Intitute of Technology

4 Pre-Lab There are many different type of diode including, large high current device for power, mall ize (mall junction capacitance) diode for rectification of high frequency AC ignal, zener diode, photodiode, light emitting diode (LED) and pn junction inide of MOSFET and BJT. They all are imilar and can be modeled with the ideal diode equation above, eq. 1. The RIT lab have 1N4004, 1N4148 diode in each lab upply cabinet, the Analog Dicover kit come with 1N4448 diode. SPICE model for thee diode are in the PSPICE Library Diode.OBL. For example the 1N4004 i model D1N4004, 1N4148 i model D1N4148 and 1N4448 i model D1N4448. If you wih to model other pn junction you can load the Dbreak component and change the SPICE model to repreent the device you wih to model. You may do thi lab with any of thee diode. (0) Look up the data heet for the diode you will be uing. Record revere leakage, max current, breakdown voltage, junction capacitance, etc. (1) Given the ideal diode theory preented in lecture and above, explain how you will plot meaured diode id vd characteritic and how you will extract the non-ideality factor n and the revere aturation current IS from your data. (2) Ue PSPICE to imulate the id vd characteritic of a diode a hown in the circuit of Figure 1. The SPICE model for the diode would be identified in part librarie a D1N4xxx. You may need to add the Diode.OBL library (ue Add library in the Place Part pull-down menu). Ue the procedure outlined in tep (1) above to extract the non-ideality factor n and the revere aturation current IS from your imulated data. Thi will erve a a comparion to experimentally determined value. (3) Ue PSPICE to imulate the half-wave rectifier circuit of Figure 2. Ue a inuoidal ignal for v(t) with peak-to-peak amplitude of 10 V and frequency of 60 Hz. Ue the 1N4004 diode model for the diode o you have a legitimate comparion to experimental meaurement. Determine the conduction ratio and the peak offet. Alo, baed on the theory preented above, extract value of rd and VD0. (4) Ue PSPICE to imulate the half-wave rectifier circuit of Figure 4. Ue a inuoidal ignal for v(t) with peak-to-peak voltage of 10 V and frequency of 60 Hz. Determine the ripple voltage, Vr. Analog Electronic EEEE 480 Lab #1: Diode Characteritic and Rectifier Circuit Rev2019v1 Page 4 of 7 Rocheter Intitute of Technology

5 Lab Exercie (1) Contruct the circuit hown in Figure 1. Make ure that you meaure and record the actual reitance of your nominal 330 reitor. Uing a 0 to 10 V ramp a the input ource (v), meaure the diode voltage and current for one cycle. Tranfer the data from the ocillocope to Excel. (Alternatively, you may et v manually uing a power upply and meaure the reulting vd and id. Thi mut be done for at leat five (5) poitive value of v.) Tabulate your data and draw the diode characteritic curve (id v. vd). Note: Student who have the Analog dicovery module from Digilent may et it up a a curve tracer. Set the waveform generator for a -5 volt to 5 volt awtooth. Ue a 100 ohm erie reitor. Ue the ocillocope to meaure the voltage acro the diode and the voltage acro the 100 ohm reitor. Select the math function to plot the current veru voltage. (ee: the reference document ) (2) Contruct the half-wave rectifier circuit hown in Figure 2. Make ure that you meaure and record the actual reitance of your nominal 1 k reitor. Ue a inuoidal ignal for v(t) with peak-to-peak voltage of 10 V and frequency of 60 Hz. Oberve and plot the voltage waveform of the ource voltage v(t) and the output voltage vo(t). From the plot, meaure the peak value of v(t), the peak value of vo(t) and the interval of time in each cycle when the diode i conducting. (3) Contruct the modified half-wave rectifier circuit hown in Figure 4, a 10 F capacitor. Ue a inuoidal ignal for v(t) with peak-to-peak voltage of 10 V and frequency of 60 Hz. Oberve and plot the voltage waveform of the ource voltage v(t) and the output voltage vo(t). Analyi of reult (1) Uing the data collected from the circuit of Figure 1 in Part (1) of the Lab Exercie, and following the methodology outlined in Part (1) of the Pre-Lab preparation, extract the diode parameter n and IS. Compare your experimental value to thoe obtained through imulation in your pre-lab preparation. (2) Uing the data collected from the circuit of Figure 2 in Part (2) of the Lab Exercie, extract the non-ideal diode parameter rd and VD0 (a hown conceptually in Figure 3). Alo, calculate the conduction ratio and the peak offet from your experimental meaurement. Compare your experimental value to thoe obtained through imulation in your pre-lab preparation. (3) Uing the data collected from the circuit of Figure 4 in Part (3) of the Lab Exercie, determine the ripple voltage, Vr. Compare your experimental value to that obtained through imulation in your pre-lab preparation. Alo, baed on ripple theory from lecture and the text, calculate the expected value of ripple voltage and compare it to your experimental and imulated value. Analog Electronic EEEE 480 Lab #1: Diode Characteritic and Rectifier Circuit Rev2019v1 Page 5 of 7 Rocheter Intitute of Technology

6 Check-Off Sheet A. Pre-Lab Explanation of how to obtain n and IS. SPICE imulation of the 1N4004 id vd characteritic and extraction of n and IS. SPICE imulation of the half-wave rectifier circuit, and determination of the conduction ratio, the peak offet, rd and VD0. SPICE imulation of the modified half-wave rectifier circuit with capacitor, and determination of the ripple voltage, Vr. B. Experimental Obtain diode characteritic curve (id v. vd). Extract n and IS and compare to imulated value. Meaure the repone of the half-wave rectifier circuit (Figure 2 and 3) and obtain value for the peak of the ource voltage v(t) and the output voltage vo(t), a well a the conduction interval. Calculate the conduction ratio and the peak offet. Extract the non-ideal diode parameter rd and VD0 from your experimental meaurement and compare to value obtained through imulation. Meaure the repone of the modified half-wave rectifier circuit with capacitor (Figure 4) and obtain value for the maximum and minimum output voltage. Determine the ripple voltage, Vr. Compare your experimental value to thoe obtained through imulation and theoretical calculation. TA Signature: Date: Analog Electronic EEEE 480 Lab #1: Diode Characteritic and Rectifier Circuit Rev2019v1 Page 6 of 7 Rocheter Intitute of Technology

7 Appendix B: Component Available in the Electrical Engineering Lab (other value available on requet) 100 Ω 1.2 kω 3.9 kω 15 kω 1 MΩ 0.01 µf 330 Ω 1.5 kω 4.7 kω 33 kω 1N µf 470 Ω 1.8 kω 5.6 kω 47 kω 1N404 1 µf 820 Ω 2.2 kω 6.8 kω 100 kω 1N µf 1 kω 3.3 kω 10 kω 470 kω 1N µf 2N3904 2N3906 2N4401 2N4403 Created: 8/11/2012 Analog Electronic EEEE 480 Lab #1: Diode Characteritic and Rectifier Circuit Rev2019v1 Page 7 of 7 Rocheter Intitute of Technology