EE 330 Laboratory 9. Semiconductor Parameter Measurement and Thyristor Applications

Transcription

1 EE 330 Laboratory 9 Semiconductor Parameter Measurement and Thyristor Applications Spring 2011 Objective: The objective of this laboratory experiment is to become familiar with using a semiconductor parameter analyzer for extracting model parameters for devices. A second objective is to develop an experimental understanding of the operation of the bipolar transistor and on relating the experimental performance to the models that were established in the lecture part of the course. A third objective is to combine concepts about operational amplifiers, logic circuits, and thyristors in the design of a light-activated circuit. Components Needed: 2N4400 BJT, MC transistor array, Q4015L5 Triac, Q4010LS2 SCR, XE V-0.5A incandescent lamp, operational amplifier, photo transistor, photo resistor, or photodiode, and other standard electronic components. Background: Measurement of parameters that characterize the performance of electronic devices using basic test equipment is a tedious process and generally requires a dedicated circuit for measuring each parameter for each device. This makes it somewhat time consuming to accurately characterize individual devices or make comparisons from one device to another. The semiconductor parameter analyzer is a device that has been designed to provide rapid measurement of device characteristics for a wide variety of electronic devices without the need for any specialized test circuits or test equipment. In the contexts of this course, the semiconductor parameter analyzer can be used to measure the characteristics of diodes, MOSFETs, BJTs, and Thyristors. Once proficiency with the semiconductor parameter analyzer is established, a rather complete characterization of a device can be made in a few minutes or less. In this experiment we will limit our use of the semiconductor parameter analyzer to the characterization of MOS transistors and BJTs. An electronic circuit designer is often required to bring concepts from several varying backgrounds together in the design of a useful circuit or system. The last part of this experiment focuses on combining knowledge about operational amplifiers, optical detectors, logic circuits, and Thyristors in the design of a laser-activated circuit. Page 1 of 7

2 1. Measurement of MOSFET parameters The parameters μcox, VT0, λ and γ are key parameters that characterize the MOS transistor along with the physical parameters W and L. Most of these parameters can be measured with standard test equipment or can be obtained from a semiconductor parameter analyzer which is a piece of equipment especially designed for extracting such parameters. In a previous experiment you extracted these parameters from special test circuits that you built. In this experiment, these same parameters will be obtained using a semiconductor parameter analyzer. The parameters obtained with the semiconductor parameter analyzer will be compared with the results obtained in the previous experiment and with the parameters predicted by the manufacturer on the datasheet for the part. These parameters are the parameters that appear in the device model equations which, for the purpose of this experiment, is assumed to be the square law model where 0 V <V W VDS ID μcox VGS VT VDS V GS>VT and V DS<VGS -VT L 2 W 2 μc V V 1V V >V and V >V -V 2L OX GS T DS GS T DS GS T GS V = V + -V - (2) T T0 BS T (1) Measure the parameters μc OX, VT0, λ and γ for the NMOS transistor (the one with the gate on pin 3) in the MC14007 array using the Agilent 4155 Semiconductor Parameter Analyzer. Compare the results obtained with those measured in a previous experiment and with what is given on the datasheet. Compare your values with groups around you and show them to your TA. There are several data sheets for this array around and most are very terse with little useful information. The one attached to this laboratory experiment is reasonably complete and should be adequate for this experiment. It is also available from the WEB site Page 2 of 7

3 Part 2 Measurement of BJT Parameters The parameters I S, β, and V AF are key parameters that are used to chararize the operation of the bipolar junction transistor. These parameters appear in the forward active model for the BJT that relate the dependent variables IB and IC to the independent port voltages VBE and VCE given by the equation VBE V V t CE I C = ISe 1+ V AF V > 0.4V, V < 0V IS I B = e β V V BE t BE BC (3) where V=kT. t q Measure the parameters IS, β, and VAF for the 2N4400 Bipolar Junction Transistor using the Agilent 4155 Semiconductor Parameter Analyzer and compare with the values given in the manufacturers data sheet. You will compare these parameters with those obtained by using standard test equipment in the next experiment. Mark the transistor you used for these measurements so that you can compare parameters for the same device. Compare your values with groups around you and show them to your TA. Part 3 Measurement of the Output Characteristics of Transistors The output characteristics of a MOSFET are the relationships between the drain current I D and drain to source voltage, V DS, for different values of V GS. These characteristics represent the actual input-output relationships of the device and are valid in all regions of operation of the transistor. The device models that have been developed are approximations to the actual output characteristics of the device. Correspondingly, the output characteristics of a BJT are the relationship between the collector current I C and collector to emitter voltage, V CE, for different values of either I B or V BE. These characteristics represent the actual input-output relationships of the device and are valid in all regions of operation as well. The device models that have been developed are approximations to the actual output characteristics of the device. Using the semiconductor parameter analyzer, obtain the output characteristics for the 2N4400 BJT. Specifically, plot IC versus VCE for values of IB between.4ma and 1.4mA with.2ma steps. Compare the output characteristics with those in the manufacturer s datasheet. The general form of the output characteristics of a BJT are shown in the following figure. Show your plot to the TA. Page 3 of 7

4 I C V BE5 V BE4 V BE3 V BE2 V BE1 Fig. 2 Functional Form of Output Charactristics for the BJT V CE Part 4: Laser Pointer Controlled Load Design, build, and test a circuit whereby an incandescent lamp can be turned on or turned off with a laser pointer. When the laser pointer is directed to the ON Target (depicted in green) the lamp should be turned on. When the laser pointer is directed at the OFF Target (depicted in red), the lamp should be turned off. When turned on, it should remain in the ON state until turned off. When turned OFF, it should remain off until turned on. The laser pointer targets should not be adversely affected by ambient light in the room and should be separated from the laser pointer by 10 feet or more. ON Target Laser Pointer OFF Target 10 feet or more Fig. 3 Block diagram of Laser-controlled Lights The incandescent lamp should be the 24V, 500mA lamp that was used in the previous experiment. Demo your circuit for the TA. Page 4 of 7

5 Part 5: Measurement of Output Characteristics of Diodes (extra credit) where The diode is normally characterized by the diode equation given by the expression VD V t I D =ISe -1 (6) V=kT, V t q D is the voltage from anode to cathode of the device, and I D is the current flowing into the anode. The transfer characteristics of the diode represent the actual relationship between the I D and V D. The parameter I S is chosen to obtain a good fit between the model of the device and the actual device characteristics. As for the MOSFET and BJT, the semiconductor parameter analyzer can be used to obtain both model parameters and transfer characteristics for the diode. Using the semiconductor parameter analyzer, measure the transfer characteristics for the 1N4148 diode and the RED LED in your parts kit and compare measured results with those obtained from the manufacturer s data sheets. Part 6: Measurement of Output Characteristics of Thyristor (extra credit) The transfer characteristics of thyristors must be known to practically utilize these devices. A plot of the typical transfer characteristics of both the SCR and the Triac are shown in the following figure. As for the MOSFET and the BJT, Thyristors are 3-terminal devices and a semiconductor parameter analyzer can be used to characterize the transfer characteristics. Unlike the MOSFET and BJT we have been using in the laboratory experiments conducted in this course, some of the transfer characteristics of the Triac and the SCR that are of interest involve large voltages In particular, the voltages VBGF and VBRR are often very large and for many devices, the current that would flow if VBGF were measured would cause excessive power dissipation that would destroy the device. Likewise, the current must be limited to avoid destroying the device if attempts are made to measure VBRR. However, the transfer characteristics of the device near the trigger state, that is, for various gate currents where the break-over voltage is small, can be readily measured in the laboratory or with a semiconductor parameter analyzer. Measure the transfer characteristics of either the Q4015L5 Triac or the Q4010LS2 SCR for gate currents in the vicinity of the trigger current and compare measured results with those provided in the manufacturer s datasheet. When measuring characteristics of the Triac, consider triggering in both Quadrant 1 and Quadrant 3. Page 5 of 7

6 I F V BRR V BGF I G4 >I G3 >I G2 >I G1 =0 V F (a) I F -V BGF I G4 >I G3 >I G2 >I G1 =0 V BGF V F Deliverables 1. MOS Parameters (b) Fig. 4 Typical transfer characteristics of Thyristors a) SCR b) Triac Page 6 of 7

7 2, BJT Parameters 3. BJT Output characteristics 4. Laser Pointer Light Page 7 of 7