Diode experiment pdf

Diode Voltage V. Resistor Voltage. In fact, running the described sequence backwards guess the diode voltage, calculate the current, find the resistor voltage drop, and subtract from the battery voltage to refine the diode voltage guess does not converge.

Try it yourself! The study of the convergence of these methods is called Iterated Map Theory, and, surprisingly, is the basis for Chaos Theory. Both the load line analysis and the iterative analysis yield the same values for the equilibrium voltage and current.

Note that the diode equation [Eq. With some loss in precision, experimental data taken from an actual diode can be used instead. Perturbation Analysis. The general subject of the response of a system to small parameter changes perturbations is called perturbation analysis.

In the circuit of Fig. I Graphical Perturbation Analysis. By definition perturbation analysis considers only small changes to the system parameters. Consequently it is both convenient and permissible to linearize around the equilibrium conditions.

Thus, a curved characteristic curve becomes a straight line. Using the circuit in Fig. This perturbation will shift the load line upwards as shown at right, and the intersection will shift concomitantly. The small signal impedance is the reciprocal of the slope of the diode characteristic curve at the operating point. Problem 3. Obtain a 1N diode. The label 1N designates the type of diode. Tens of thousands of different types of diodes are available.

Many types are made by several different manufacturers; each manufacturer certifies that their diode meets the industry-wide specifications. Parts with labels that begin with 1N are always diodes, while parts that begin with 2N are transistors, but not all diodes and transistors follow this naming convention. Specifications for the 1N diode are on the Physics Library site. This lab also uses another type of diode, the 1NB which is very difficult to differentiate from the 1N visually.

Make sure that you do not mix up the two types, and make sure that you return your diode to the proper drawer. Set the DMM to the diode scale. On the handheld Fluke DMM, this is the scale indicated by the yellow diode symbol ; make sure that you press the yellow "shift" button to toggle between this scale and the continuity scale.

On the benchtop Kiethley DMM, this is the scale indicated by the blue diode symbol ; make sure that you use press the blue "shift" button before you go to this scale. With the Double Banana plug ground hooked up to the COM Fluke or LO Keithley Banana input plug, the red minigrabber lead will be positively biased referenced to the black lead; thus, for diode conduction, the red lead should be attached to the diode anode, and the black lead should be attached to the cathode.

On the diode itself, the cathode is marked by a black band; in the 1N image above, the band is at the bottom. Confirm that the diode conducts unidirectionally by measuring the forward voltage drop when the diode is forward biased, and an error code when the diode is reversed biased. Obtain a plastic-stick-mounted 1N diode from the laboratory staff. Repeat your measurement of the forward voltage drop using the DMM. Does this diode have exactly the same forward voltage drop as the diode you used in part 3.

Forward voltage drops vary between types of diodes and even between diodes of the same type. Squeeze the diode between you fingers. The forward voltage drop should change as the diode heats up to your finger temperature. What is the new value? For more dramatic results, dip the diode into liquid nitrogen, which you can obtain from the laboratory staff. What is the forward voltage drop now? Diodes are frequently used as temperature sensors by measuring this forward voltage drop.

Warning: Because diodes of the same type can have significantly different characteristics, use the same diode for all experiments in this lab. If you need to use your diode on another day, mark it with a piece of tape with your name and leave it in the storage cubbies in the back of the lab.

Now examine the behavior of the Offset Adder circuit included on the breadboard box at your lab station. A picture of the offset adder, and a brief description of its functionality, cae be found in the Lab 1 manual immediately after Problem 1. Temporarily ignore the input BNC jack. Try loading the output with several different resistor values.

By plotting a V-I curve, prove that the circuit is a relatively stiff low output impedance voltage source so long as the output current is kept below approximately 24 mA. DMM resistance measurements are a useful crude indicator of diode performance, and are often used to determine if a diode has been burnt out.

However, DMM measurements are single current measurements, and do not determine the complete relation between the diodes forward voltage and the forward current. To measure the diode characteristic curve, construct the circuit shown at right. Use the stick-mounted diode that you used in exercise 3. Vary the voltage across the diode with the offset adder.

Concentrate on voltages near the forward bias voltage that you found previously, and make sure that you stay below the current limit that you found in exercise 3. Plot the resulting characteristic curve on linear and on log-linear paper.

If you measure the voltage at the offset adder, on the other side of the current meter, you will also measure the small, but not necessarily negligible, voltage across the current meter. Obtaining enough points to carefully characterize the diode is tedious. Furthermore, the slow rate at which the data can be collected by hand causes the diode to heat up significantly at the high current points, disturbing the measurement.

A Curve Tracer is an instrument that automatically, and relatively quickly, measures characteristic curves. Operating information about the curve tracer can be found here: Curve Tracer Manual. Use the Curve Tracer to find your diodes characteristic curve. Export the Curve Tracer data to a file, and p lot the points on a graph.

Save this data for future use. Add the points that you obtained in problem 3. Superimpose the cold diode data on your room temperature diode data graph. Build the circuit at right. The current is too small to measure directly, so use the Keithley DMM to measure the voltage across the resistor, and Ohm's law to infer the current.

Using the same diode as before, build the circuit shown at right. Again measure the current and output voltage for several input voltages. Using the graph of the diode characteristic you obtained in problem 3. Do the equilibrium points predicted by the load line analysis agree with your data? Connect the signal generator to the input of the Offset Adder. Since diodes carry current only in one direction, they can be used to rectify AC signals; rectify means to convert an AC signal into DC. Consequently, diodes are sometimes called rectifiers, especially when used in this application.

There are a few electronic circuits, like light dimmers and some electric motor controllers, that run off of AC.

Most non-battery-powered electronics, however, require that the AC from a wall socket be converted to DC. Build the half-wave rectifier circuit at right. Display the output of the signal generator on channel 1 of the scope, and the voltage across the resistor on channel 2.

This latter voltage is the output of the circuit. Save images of the traces, and explain all the features of the output voltage. Rectification, as provided by the previous circuit, is only the first step in converting AC power into DC power. The gross irregularities in the signal produced by the above circuit needs to be smoothed out, typically by a high-capacitance filter capacitor. Because of technological limitations, the "ceramic" capacitors that you have been using up to now do not have sufficiently high capacitance to be used in this application.

Consequently, t he exercises below use electrolytic capacitors. Unlike ceramic capacitors, electrolytic capacitors are polarized. One lead of a polarized capacitor must be held at a negative potential relative to the other. The negative lead is typically marked with a stripe containing stylized minus signs or zeros, and sometimes with an arrow. Alternatively, axial capacitors are sometimes marked with a detent and plus signs on the positive lead.

Three styles of electrolytic capacitors are shown at right. Radial Capacitor. Negative lead on top. Axial Capacitor I. Negative lead at right. Axial Capacitor II. Positive lead at left.

What happens if you reverse bias a capacitor? They can explode Even if the capacitor doesn't explode, it will be damaged if it is ever reversed biased: its capacitance will go down, and its leakage resistance a resistance through the capacitor that is infinite in an ideal capacitor, and nearly so in a ceramic capacitor will diminish.

In general, electrolytic capacitors will not perform as well as ceramic capacitors. Always use a ceramic capacitor if one is available in the required size. Electrolytic capacitors and a slightly better performing type of capacitor called a tantalum capacitor should only be used for applications like rectification filtering.

Never use one for a normal high or low pass filter, and never use them in circuits in which they can ever be reverse biased. If you use an electrolytic capacitor, make sure you obey the polarity markings on the capacitor body.

Save images of the output waveform. Note the amplitude of the ripple. See analysis question 3. GaAs junctions have the very useful property that they emit light when forward biased. Construct the circuit at right using a red LED for the diode. The LED should not light. Measure the voltage across the resistor to demonstrate that no current is flowing. Now swap the power supply polarity; the LED should now light.

Measure the voltage drop across the resistor and LED. How does the brightness of the LED change? How does the forward voltage drop change? How much current is required to light the LED? Compare the characteristic curves of red, green, and blue LEDs.

What fundamental constant partially explains your observations? Circuits frequently require DC voltages less than the circuit power supply voltage. Such voltages can be obtained with voltage dividers, but dividers are not stiff and, consequently, their output voltage will decrease when loaded. Furthermore, the divider voltage will follow any power supply voltage fluctuations. Better schemes use a device called a Zener diode. Zener diodes are diodes deliberately optimized for use in the reverse breakdown region.

Using a Zener diode in the lower leg, you can make a voltage divider-like circuit whose ouput voltage is quite stiff, i. Design and build a circuit with the Zener that will reduce a voltage from 12V to 6. Hint: considering the Zener's characteristic curve, should the Zener be forward or reverse biased? Therefore, by using separate R0A sd for lower and V. The R0A bulk and perimeter and create a shunt path for the total current.

R0A sd fitting parameters for each temperature are listed in Table 1. Rogalski, HgCdTe infrared detector material: history, status and tunneling at the surface.

Jhonson et al [7] have reported outlook, Rep. Chung, M. Rosenberg and P. Pultz, P. Norton, E. Eric, Krueger, M. Gopal, Variable area diode data analysis of surface and bulk effects in HgCdTe photodetector arrays, Semicond.

Ashokan, N. Dhar, B. Yang, A. Akhiyat, T. Lee, S. Rujirawat, S. Yousuf and S. Johnson, D. Rhiger, J. Rosebeck, J. Peterson, S. Taylor and M. Gopal, A general relation between zero bias resistance area product and Fig. Temperature perimeter to area ratio of the diodes in variable area diode test structures, was varied from 80 K to K.

As the temperature increases Semicond. Bajaj, E. Blazejewski, G. Williams, R. DeWames and M. HgCdTe defects.

Table 1: Variable temperature data for tile 6. Norton, Anthony P. Erwin, Etch pit study of dislocation formation in Hg1-xCdxTe during array hybridization and its effect on device performance, J. Grimbergen, The influence of geometry on the interpretation of the 80 Reine, A. Sood and T. Tredwell, Semiconductors and 93 Related Papers.

By Petter Minnhagen. By aslam farooq. By Saroj Rujirawat. Uniformity in HgCdTe diode arrays fabricated by reactive ion etching. By Vikram Kumar. By mauro vilela. Download pdf.

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