Jfet characteristics lab report

Jfet characteristics lab report

Jfet characteristics lab report
You will compare the experimental results with the theoretical results of the equations found in the lab manual. Information essential to your understanding of this lab: 1. Standard testing station 2. This list is not all inclusive; however, it does contain the most common symbols and their units. Table 1. Chart of the symbols used in this lab. Table 2. Chart of the equations used in this lab. Unlike diodes, which have two terminals that we call the cathode and anode; JFETs have three terminals that we call the source, drain and gate. The resistance between the drain and source terminals RDS is controlled by the voltage applied between the gate and source terminals VGS. Since we rarely care about the actual resistance in these devices, but rather about the current flowing through them, we note that the transistor action in a JFET is determined by the flow of majority carriers between the source and the drain IDS as a function of VGS. This reduces the cross sectional area of a channel through which the charge carriers IDS must flow in order to go from source to drain. See Streetman and Banerjee section 6. The gate voltage modulates the depletion width of the gate-source pn junction. When the depletion width is made larger larger VGS reverse bias the channel cross sectional area is made smaller and the resistance is made larger. The change in the cross-sectional area of the channel under the gate modulates the current flow. The most important operating region of the JFET occurs at VDS levels beyond the point where the channel cross sectional area becomes zero. The points at which this closing of the channel first occurs are shown in Fig. The places where the data curves intersect the red curve are called the saturation voltages and denoted as VDSAT. The one place where the red curve in Fig. The depletion width extends all the way across the channel, pinching it off at the drain side so that the channel cross sectional area becomes zero. This closing of the channel does not cause the resistance of the channel to go to infinity, just the differential resistance to go to infinity. The current flow is now limited by the current flow in the non-pinched off region of the channel. The carriers which reach the pinched off region are rapidly pushed through by the reverse bias of the gate and collected at the drain. Analysis of the device geometry shows that in the pinched off region the current flow is primarily determined by the value of VGS and is relatively independent of VDS. This is the practical region for operating the JFET as an amplifier. This is shown in Fig. Detailed information about the characteristics of the device is almost always supplied by the device manufacturer so that engineers can design circuits using them. In rare circumstances, the circuit designer must measure device characteristics or use more limited information supplied by the manufacturer such as IDSS and VP. VGS V Fig. Transfer characteristic IDS vs. The solid red line is a fit using Eqn. The slope of this curve gives the transconductance, gm. We can allow VGS to go slightly positive without destroying the JFET operation since that slightly positive gate voltage will only thin the depletion region without allowing significant current IGS to flow through the gate. The values of IDSS and VP for a given type of transistor vary over ranges, therefore the device manufacturer supplies information on the average and extreme values of these parameters. Moreover the device may not closely obey the relationship given by Eq.

Jfet characteristics experiment

N-Channel junction field effect transistor characteristics laboratory experiment using the 2N through 2N series general purpose JFET. The experiment will expand on and verify theoretical concepts presented in the lecture course Analog and Semiconductor Devices through the use of bench top device measurements, hand calculations, and PSpice simulations. Equipment and Materials: 1. DC Power Supply, 2 each 2. Digital Multimeter, 2 each 3. Curve Tracer 4. Assorted resistors. Procedure: 1. ID vs. Plot the results on graph paper. Use bench instruments to find VGSoff e. Repeat steps 1 through 5 for a second 2N Plot the curve tracer measured transfer curves for both JFETs on the same set of axes. Use graph paper. See Figure 4 for an example. Figure 4. Construct the circuits shown in Figures 1, 2 and 3 using values calculated in step 8. For each circuit: a. Compare the results to the measured values obtained in step 9a. In starting this experiment it was found that one of the 2N JFET's previously used in experiment one had failed so a replacement device was introduced for this experiment. By examining the 2N JFET devices using three separate techniques provides one to better understand the characteristics of the device and will assist in design specifications for complex circuits. In closing, the 2N JFET device was examined even more closely then in experiment one with the use of specific measurements taken from bench test equipment. It was discovered that the measurements taken off the curve tracer scope were very similar to those measurements taken. Also in a final comparison, Pspice simulations were ran and when compared to the gathered data, all data agreed within acceptable error limits. Overall the characteristics of the 2N JFET devices were learned and a general understanding of the outputs will provide one with a better understanding for using the device in an applied application. Analog Semiconductor Devices. Lab Experiment 1. Lab Experiment 2. Lab Experiment 3. Lab Experiment 4. Lab Experiment 5. Lab Experiment 6.

Fet characteristics experiment readings

Jfet characteristics lab report
To browse Academia. Skip to main content. Log In Sign Up. Lab Report 4. Sanzhar Askaruly. Analog Electronics Lab Report 4 Lesson 8. From theory, we know that Field Effect Transistors are voltage controlled unlike from BJTs, which are current controlled devices. There are Source, Gate and Drain electrode sides. The Gate electrode voltage is used to control Drain-Source characteristics. In this lab, we are to obtain the results in order to prove above said. Determining the output characteristic of a JFET: In this exercise we are to find the drain current by varying drain-source voltage. In order to achieve this goal the circuit shown in Figure 1. Figure 1. What has happened in the circuit? This can be easily explained by considering that there is a short circuit between drain and souce. From experiment, we can state that this voltage starts approximately at 8 V and the drain current approaches Task 8. Determining the transfer characteristic: In this task we are to determine the transfer characteristics of the FET. The circuit presented below is applied into the board. How can the graph if ID best be described? The maximum drain-source current is reached when gain is shorted to ground. Also, it was empirically observed that the pinch-off voltage when there is no current equals approximately Lesson 9: Amplifier Configuration 9. Common Emitter Circuit This exercise is started with common emitter circuit. One of the purposes of this circuit is to increase the output voltage. The curve produced has a characteristic similar to a: c diode characteristics mode. The curve resembles the diode characteristic graph. VBE converges to some value, which is approximately 0. After this value there is short circuit. Therefore, the curve is similar to inverted diode curve which is in forward bias operation mode. For small values of IB the curves are parallel in the linear region. In the linear region the static output resistance is high. Common Collector Circuit One type of amplifier circuits is common collector circuit usually used to buffer voltage. Base terminal serves as input. The emitter electrode as output and the collector is common.

Jfet characteristics experiment readings

Jfet characteristics lab report
Bipolar Junction transistors BJT were tackled in Electronics Engineering 1 and in this experiment, a new type is introduced. The voltage across RD Drain resistor was measured and divided by and the I D drain current was acquired upon computing and was then recorded. Steps were repeated until desired data were obtained. For the VGS value of 0. As seen below. These minute discrepancy might be due to external factors like systematic errors, faulty calibration, instruments or materials or random error, unpredictable variations. This is for the reason that in order to vary the output of the transistor the input voltages are the ones controlled and adjusted while comparing it on how a BJTs output is achieved where the input voltage stays the same but the resistance in the base assuming a Common Emitter Configuration varies. The graphs also show a considerable difference of the curve of the two types of transistors under comparison where JFETs curve gradually became horizontal while BJTs curve abruptly approached a slope of zero. Therefore, a JFET has a very high input resistance where it will take a reasonable change in input to change the output. Muito mais do que documentos Descubra tudo o que o Scribd tem a oferecer, incluindo livros e audiolivros de grandes editoras. Iniciar teste gratuito Cancele quando quiser. Enviado por bravo5charlie. Data de envio Dec 28, Denunciar este documento. Baixe agora. Experiment 6 Transformer Voltage Regulation and Efficiency. Pesquisar no documento. As seen below III. Output data VDS 0. Graphs 1 0.

Conclusion for jfet experiment

As this figure depicts, the N-channel JFET is made of N-type semiconductor material with two islands of P-type materials embedded in the middle sides of this material. One end of the N-type channel is called "Source" while the opposite end is called "Drain". The two P-type materials in the middle are internally connected and are referred to as the "Gate". It is through this narrow channel that the free electrons in the N-type material must pass as they move from the source to the drain. Thus, when a negative voltage is applied on the gate, the induced electric field in this P-material gate will control the flow of electrons between the source and the drain. Therefore, the JFET is a voltage-controlled device. In biasing the N-channel JFET, a positive voltage V DD is connected between the drain and the source thus allowing for the free electrons to flow from the source to the drain. Since these electrons must pass through the gate region channelthis would provide means for controlling the current flow from the drain to the source. This is done by applying negative voltage across the gate region to impede the movement of the electrons passing through it. Notice that the negative gate supply V GG is connected between the gate and the source. This is standard for all JFET applications. The gate of the JFET must always be reverse biased to prevent electric current from flowing into the gate. However, the reverse bias introduces depletion layers around the gate region P-region as shown in Figure 2 b. Thus, increasing the negative voltage on the gate will make the conduction channel across the gate narrower. The more negative the gate voltage the narrower the channel becomes because the depletion layers get closer together. In this case the drain-source current is cut-off. The gate voltage in this case is called the "Pinch-off" voltage V p-off. On the other hand, when V GG is set to zero, the pinch-off region will disappear and the current from the drain to the source will be free to flow, only controlled by the resistance of the N-type materials forming the N-type channel see Figure 1. As a result, this current is the maximum drain current a JFET can produce for a given drain-to-source voltage before the transistor goes into breakdown. This current is typically referred to as I DSS. The trans-conductance characteristic of the JFET is a set of graphs relating the drain current to the gate voltage, i. I D versus V GS. In analytical form, this relationship is universally given as. The pin connection diagram for the 2N transistor is as shown in Figure 3.

Drain and transfer characteristics of jfet experiment

Jfet characteristics lab report
With a drain-source voltage applied as illustrated, I D flows in the direction shown producing voltage drops along the channel. Consider the voltage drops from the source terminal S to points A, B. Point A is positive with respect to the source: alternatively, it can be stated that S is negative with respect to A. Because the gate blocks are connected to S, the gates are negative with respect to point A by a voltage V A. This causes the depletion regions to penetrate into the channel by an amount proportional to V A. Consequently, at point B on the channel the gates are at -V B with respect to the channel, and the depletion region penetration is less than at point A. Thus, the gate-channel reverse bias at point C is V C volts, and the depletion region penetration is less than at point A or B. The differing voltage drops along the channel, and the resulting variation in gate-channel reverse bias, accounts for the shape of the depletion region penetration of the channel. There is no channel voltage drop, so the voltage between the gate and all points on the channel is zero, and there is no depletion region penetration. This results in some depletion penetration of the channel as explained for Fig. The channel continues to behave as a fixed-value resistance until the voltage drops along it become large enough to produce considerable depletion region penetration. At this stage the channel resistance begins to be affected by the depletion regions. The increased I D levels, in turn, cause more depletion region penetration and greater channel resistance. At the point on the characteristic where I D levels off, the drain current is referred to as the drain-source saturation current I DSS. When this occurs, I D increases rapidly, and the device might be destroyed. The pinch-off region of the characteristic is the normal operating region for the FET. A family of drain characteristics can be obtained by using several levels of negative gate-source bias voltage, see Fig. The dashed line on the characteristics in Fig. When a -1 V external bias is applied, the gate-channel junctions still require The 2. Suppose a Note on Fig. As illustrated in Fig. Figure b shows a circuit for experimentally determining a table of quantities for plotting the transfer characteristic of a given FET. The transfer characteristic for a FET can be derived from the drain characteristics. A line is drawn vertically on the drain characteristics to represent a constant V DS level. Note the direction of the arrowhead on the PET symbol, and the drain current direction. Also, note the supply voltage polarity, and the polarity of the gate-source bias voltage. The drain terminal is negative with respect to the sourceand the gate terminal is positive with respect to the source. To obtain a table of quantities to plot a drain characteristic, V GS is maintained constant at the desired positive level, -V DS is increased in steps from zero, and the I D levels are noted at each step. It is seen that these are similar to the characteristics for an n-channel JFET, except for the voltage polarities. In Fig.

Output characteristics of n-type jfet

Bipolar Junction transistors BJT were tackled in Electronics Engineering 1 and in this experiment, a new type is introduced. The voltage across RD Drain resistor was measured and divided by and the I D drain current was acquired upon computing and was then recorded. Steps were repeated until desired data were obtained. For the VGS value of 0. As seen below. These minute discrepancy might be due to external factors like systematic errors, faulty calibration, instruments or materials or random error, unpredictable variations. This is for the reason that in order to vary the output of the transistor the input voltages are the ones controlled and adjusted while comparing it on how a BJTs output is achieved where the input voltage stays the same but the resistance in the base assuming a Common Emitter Configuration varies. The graphs also show a considerable difference of the curve of the two types of transistors under comparison where JFETs curve gradually became horizontal while BJTs curve abruptly approached a slope of zero. Therefore, a JFET has a very high input resistance where it will take a reasonable change in input to change the output. Learn more about Scribd Membership Home. Read Free For 30 Days. Much more than documents. Discover everything Scribd has to offer, including books and audiobooks from major publishers. Start Free Trial Cancel anytime. Uploaded by bravo5charlie. Document Information click to expand document information Description: Lab Report. Date uploaded Dec 28, Did you find this document useful? Is this content inappropriate? Report this Document. Description: Lab Report. Flag for inappropriate content. Download Now. Related titles. Carousel Previous Carousel Next. Experiment 6 Transformer Voltage Regulation and Efficiency. Jump to Page. Search inside document. As seen below III. Output data VDS 0. Graphs 1 0. Than Lwin Aung. Diana Jane Terez Lazaro. Amalina Ismail. Katherine Ann Yutoc. Aasiq Mohamed.

Fet experiment manual

A transistor is a linear semiconductor device that controls current with the application of a lower-power electrical signal. Transistors may be roughly grouped into two major divisions: bipolar and field-effect. In the last chapter, we studied bipolar transistors, which utilize a small current to control a large current. All field-effect transistors are unipolar rather than bipolar devices. That is, the main current through them is comprised either of electrons through an N-type semiconductor or holes through a P-type semiconductor. This becomes more evident when a physical diagram of the device is seen:. In a junction field-effect transistor or JFET, the controlled current passes from source to drain, or from drain to source as the case may be. The controlling voltage is applied between the gate and source. Note how the current does not have to cross through a PN junction on its way between source and drain: the path called a channel is an uninterrupted block of semiconductor material. In the image just shown, this channel is an N-type semiconductor. P-type channel JFETs are also manufactured:. As with bipolar transistorsI believe the best way to introduce field-effect transistor usage is to avoid theory whenever possible and concentrate instead on operational characteristics. The only practical difference between N- and P-channel JFETs you need to concern yourself with now is biasing of the PN junction formed between the gate material and the channel. With no voltage applied between gate and source, the channel is a wide-open path for current to flow. However, if a voltage is applied between gate and source of such polarity that it reverse-biases the PN junctionthe flow between source and drain connections becomes limited or regulated, just as it was for bipolar transistors with a set amount of base current. This behavior is due to the depletion region of the PN junction expanding under the influence of a reverse-bias voltage, eventually occupying the entire width of the channel if the voltage is great enough. This action may be likened to reducing the flow of a liquid through a flexible hose by squeezing it: with enough force, the hose will be constricted enough to completely block the flow. Note how this operational behavior is exactly opposite of the bipolar junction transistor. Bipolar transistors are normally-off devices: no current through the base, no current through the collector or the emitter. JFETs, on the other hand, are normally-on devices: no voltage applied to the gate allows maximum current through the source and drain. Also, take note that the amount of current allowed through a JFET is determined by a voltage signal rather than a current signal as with bipolar transistors. In fact, with the gate-source PN junction reverse-biased, there should be nearly zero current through the gate connection. For this reason, we classify the JFET as a voltage-controlled device and the bipolar transistor as a current-controlled device. However, the PN junction of a JFET is not built to handle any substantial current itself, and thus it is not recommended to forward-bias the junction under any circumstances. This is a very condensed overview of JFET operation. In Partnership with Vicor.

Fet characteristics notes

Draw a circuit for measurements of characteristics of a depletion mode, n-channel JFET, described in part 1 of the Laboratory below. V GS and explain why it may be used as a constant current source and a voltage controlled resistor. Indicate the parts of the characteristics where these functions can be realized. Equipment needed from the stockroom: ECE parts kit, analog universal meter, resistance substitution box, leads. Insert a JFET into the protoboard, connect the source to ground and the drain to a 15 V power supply through an ammeter, which will measure the drain current I D. Measure this current for different voltage values between the gate and the source V GS. Use only negative voltage on the gate. Determine the pinch-off voltage V Pi. V GS graph to determine V P. This current flows through the transistor when the gate connected to the source. Repeat measurements of V P and I DSS values for another transistor of the same type in your kit and see if there is significant difference between the two transistors. If so, make sure that you can identify these transistors when you use them in other measurements. Note the linear part of the characteristics, where I D is proportional to V DS behaves like a resistor and the saturation part, where current is almost independent of the voltage. You will explore saturation range of the JFET transistor characteristic in part 2 and the linear range in part 3, below. The flat parts of the I D vs. V DS characteristics of the FET allow to use this device as a simple constant current sources because the current is almost independent of the voltage across it. Test this idea with two transistors. How good is this current source? What is the range of voltage across the transistor operating as a current source. You can buy JFETs with the gate connected to the source, so called current regulator diodes. These two terminal devices, calibrated for different current values, are current equivalents of Zener diodes which provide a constant voltage. A variation of JFET current source, with self-biasing, is shown on the next schematic. JFET Part -2 Physics Practical (Junction Field Effect Transistor).

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