Reference / Paper
Heathkit Semiconductor Curve Tracer — Manual
- curve tracer
- semiconductor
- heathkit
- test equipment
Reference / Paper
Assembly and Operation of the 6 Eo 0 © a Or ZF Ww O> sv“ i“ 2D O N a MODEL IT HEATH COMPANY BENTON HARBOR, MICHIGAN 49022 PE1ABR Fee FTE ATEHEITS TABLE OF CONTENTS INTRODUCTION . 2... 1. 3 PARTS LIST «2 we. ke 4 Step-by-Step Assembly . 2... 1. eee ee ee a 15 Circuit Board 2. 6 wk 16 Subassembly Parts Mounting .. 1... ee eee a 29 Chassis Assembly . 2... we 30 Chassis Wiring 2. 1 1 1k ee 33 Alternate Line Voltage Wiring 2. 1 1. we ee 46 Knob Installation 2... 2. ek ee 48 Test Leads 6 ww 49 TESTS AND ADJUSTMENTS Initial Checks 2 1... 51 Oscilloscopes . 2... 52 Oscilloscope Calibration . 2... ee 54 Offset Adjustment 2.2... 56 Transistor Tests. . 2. 57 FINAL ASSEMBLY .... 2... 0. ee ee 60 OPERATION Control Functions . 2... 61 Curve Tracer Characteristics . 2... 1 0 ee a 62 APPLICATIONS General Information . 2... 6 1 ke ee ee 63 TRANSISTOR IDENTIFICATION ........0.0 000 eee eee 64 Initial Display ww ee 65 Measurements §. 2... 6 1 ee ee ee ek kk 68 INCASE OF DIFFICULTY ........ 0.0.0 2 we ee ee eee ee 88 Troubleshooting Chart . 2... 6 2 ee ee 89 SPECIFICATIONS . 1... ee 91 CIRCUIT DESCRIPTION . 2... ee ee a 93 CIRCUIT BOARD X-RAY VIEWS .......0 00 6 eee ee ew ww § 97 CHASSIS PHOTOGRAPHS ...... eee 100 IDENTIFICATION CHARTS ... 2... ee a 101 SCHEMATIC. . .(fold-out from page) 2. 1 1 we 103 WARRANTY .. 1. 1 we ee ee ee ee Inside front cover CUSTOMER SERVICE ...... 2... pee ee ee ee Inside rear cover INTRODUCTION The Model {T-1121 Heathkit Semiconductor Curve Tracer is a versatile and sophisticated instrument. It accurately measures the operating parameters of virtually all types of discrete semiconductors — gain (beta), leakage, breakdown voltage, saturation, forward conduction voltage, output admittance, linearity, capacitance effects, temperature effects, etc. The Curve Tracer also can be used to select devices for specific design applications; for sorting, inspecting, and testing semiconductors; and for troubleshooting. ° ~ os Any oscilloscope with’ horizontal sensitivity of .5 volt/division and vertical sensitivity of 1 volt/division can be used with the Curve Tracer. Connecting the Curve Tracer to the oscilloscope is easy with the plug-in cables supplied, and a calibration switch permits fast and accurate oscilloscope calibration. The following features make the Curve Tracer very versatile: e Accurate current steps from 2 wA/step to 10 mA/step in a 1, 2, 5 sequence — the steps-are variable from 0 to 9. e Accuraté voltage steps from .05 volt/step to 1 volt/step in a 1, 2, 5 sequence — the steps are variable from 0 to 9. e Two-range sweep supply — 0 to 40 volts at currents up to 1 ampere, and O to.200 volts at currents up to 200 milliamperes. e Monitored sweep voltage can be displayed from .1 volt/division to 50 volts/division in a 1, 2, 5 sequence. e Monitored sweep current — from .5 mA/division to 200 mA/division ina 1, 2, 5 sequence. e Switch selectable NPN (N channel) or PNP (P channel) testing. e Eleven current limiting resistors from 10 2 to 1 MQ to protect the device being tested. e Many internal protection devices to protect the Curve Tracer and components being tested from improper operation. Low profile styling and the sloped front panel permit the Curve Tracer to set in front of most oscilloscopes without blocking the CRT. A convenient handle provides. portability, and extra leads (included) allow you to test large devices or make in-circuit tests. The versatility, accuracy, and reliability of this test instrument make it a valuable addition to your work bench for years to come. Refer to the “Kit Builders Guide’’ for complete information on unpacking, parts identification, tools, wiring, soldering, and step-by-step assembly procedures. leh BLACK BANANA JACK (G) Figure A TESTS AND ADJUSTMENTS INITIAL CHECKS The purpose of this section of the Manual is to make sure your Curve Tracer operates Properly and will not be damaged as the result of a wiring error. A transistor or integrated circuit, for example, could be destroyed instantly by a short circuit that Causes excessive current. (_ ) Inspect the Curve Tracer for improperly soldered connections, or connections that may have been missed and not soldered. Also check for solder bridged across two or more circuit board foils, which would cause a short circuit. (_ ) Examine the chassis-mounted parts to make sure they are properly mounted and connected. (_) Besure no bare wires are touching any components or the chassis. NOTE: If a VTVM is available, make the following “Resistance Checks.” If a meter is not available, proceed to “Oscilloscopes.” RESISTANCE CHECKS These resistance checks are to make sure there are no short circuits in any of the three power supply branches. DO NOT plug in the line cord until you are instructed to do so. (. ) Set your ohmmeter on the RX100 scale. (_ ) Connect the common lead of your ohmmeter to the black banana jack (G) shown in Figure A. NOTE: The resistances in the following steps are the minimum desired. If the resistance readings are significantly less, the reason (such as a short circuit caused by a solder bridge between foils) must be determined and corrected before you proceed. As some ohmmeters use the “common” lead as the positive lead, try reversing your ohmmeter leads if you do not get the designated resistance readings. (_ ) Refer to Figure A and touch the ohmmeter probe to the foil at point @). The meter reading should be 10 kQ or more. (_.) .Touch the ohmmeter probe to the foil at point @). The meter reading should be 100 kQ or more. (_) Touch the ohmmeter probe to the black banana jack (G) and the ohmmeter common lead to point . The meter reading should be 10 kQ or more. : ( ) Disconnect the meter. CAUTION: High voltage are exposed in the Curve Tracer when the line cord is plugged into an AC outlet. Refer to the “Chassis Pho tographs” on Page 100 for the location of these high voltage areas. ©) Figure 1-7 LEFT TRANSISTOR SOCKET FLAT INSET Figure 1-8 (eee areas) OSCILLOSCOPES This section of the Manual contains special considerations for ‘Heath Oscilloscopes” and all kinds of ““AC-coupled oscilloscopes.” Therefore, if you intend to use a DC oscilloscope other than a Heath one with your Curve Tracer, you may proceed to “Oscilloscope Calibration.” HEATH OSCILLOSCOPES NOTES: 1. In the following material, X means horizontal and Y means vertical. 2. The 10-10, 10-12, 10-17, 10-18, and 10-21 will produce backward traces. That is, an NPN transistor display will be from right to left instead of from left to right, etc. 10-10 — Use the X and Y input channels. 10-12 — This oscilloscope is AC coupled. Read ‘‘AC-Coupled Oscilloscopes.” 10-14 —. This oscilloscope may not have enough horizontal gain for proper calibration. If necessary, when you perform the ‘Oscilloscope Calibration,”’ calibrate the horizontal dots on every division. Note that, in this case, all the horizontal sensitivity readings will be off by a factor of two. (Example: When the Curve Tracer is set for 1 V/division, the oscilloscope will display 2 V/division.) 10-17 — This oscilloscope is AC coupled. Read ““AC-Coupled Oscilloscopes.” 10-18 — This oscilloscope is AC coupled. Read ‘‘AC-Coupled Oscilloscopes.”” 10-21 — This oscilloscope is AC coupled. Read ‘‘AC-Coupled Oscilloscopes.” 10-102 — The horizontal input of this oscilloscope is AC coupled. To obtain DC coupling for use with the Curve Tracer, place a jumper wire from the horizontal input to TP (Test Point) on the horizontal amplifier circuit board | inside the 10-102. However, for normal oscilloscope operation, remove this jumper wire, as it interferes with the internal sweep. Note also that the horizontal portion of the trace should not extend over 10 cm or the input may be overloaded and produce distortion. 10-103 — No special considerations. 10-104 — Use the X10 position of the TIME/CM switch. If this does not provide enough gain, pull out X5 MAG knob. Do not use the X1 switch position. In some cases, you may not be able to position the dot all the way into the upper right-hand corner of the screen. 10-105 — Use the X-Y mode. AC-COUPLED OSCILLOSCOPES Oscilloscopes that are AC coupled on one or both inputs (vertical and/or horizontal) are usable with the Curve Tracer but have certain limitations. Calibration of the oscilloscope will be more difficult as the dots will ‘“‘smear’’ somewhat (see Figure 1-3 on Page 53). However, this can be reduced by using only two or three dots. When you position the dot on the oscilloscope screen, before you apply any sweep voltage, position the dot one or two divisions toward the center of the screen. When the sweep voltage is applied, the display will expand in both directions from the dot. (That is, both ways horizontally if that input is AC coupled, and both ways vertically if that input is AC coupled.) To get better looking displays, use only 2 to 5 steps/family instead of all 9. The following show the difference between displays of DC-coupled and AC-coupled oscilloscopes. { See ER ATHEITS|| —— iia) DC COUPLED 4 Figure 1-1 DC COUPLED e Figure 1-3 AC COUPLED DUE TO VERTICAL AC— COUPLING DUE TO HORIZONTAL AC = COUPLING AC COUPLED DOTS ARE BLURRED, z H Figure 1-2 Figure 1-4 Ea EIPATHEIT® OSCILLOSCOPE CALIBRATION Turn on your oscilloscope and set the controls as follows: () Set the oscilloscope for approximately .5V/division horizontal, and 1 V/division vertical. (If you have a dual trace oscilloscope, place it in the X-Y mode.) () If the vertical and horizontal inputs are switchable, place them in their DC positions. (_) Use the vertical and horizontal position controls and move the dot to the lower left-hand area of the screen. ( ) Keep the trace intensity low to protect the screen from being burned by the dot. Refer to Figure 2-1 (fold-out from Page 48) for the following steps. Set the Curve Tracer controls as follows: SWEEP VOLTAGE — Fully counterclockwise and OFF. HORIZONTAL SENSITIVITY — 1. VERTICAL SENSITIVITY — 10. POLARITY — NPN. SWEEP RANGE — 0-40V. STEP SELECTOR — CURRENT. STEPS/FAMILY — Fully counterclockwise. () STEP RANGE — 1. LIMITING RESISTOR — 100. LEFT-RIGHT — LEFT. LOOP — Center of rotation. NORM-CAL — CAL. Refer to Figure 1-5 (fold-out from Page 48) and connect the H, G, and V outputs of the Curve Tracer to the horizontal, ground, and vertical inputs of the oscilloscope. Use one black lead and two red leads with banana plugs on both ends as shown in the Figure. + e Deena Onno COE ee Oe eee Gaadn GRA RRR Pee a r HORIZONTAL e + le“ GRATICULE £ LINE [ ) aelbene FIRST DOT VERTICAL . GRATICULE Figure 1-6 LINE f HEATHEITS| SssSSSa9BMMS NOTE: In the following steps, if the Curve Tracer does not operate as described, immediately unplug the line cord and refer to the “In Case of Difficulty”’ section of the Manual on Page 88. Then correct the problem before proceeding with the “Initial Tests.’’ CAUTION: High voltages are exposed in the Curve Tracer when the line cord is plugged into an AC outlet. Refer to the “Chassis Photographs” on Page 100 for the location of these high voltage areas. (_ ) Plug the line cord plug into an AC outlet of the proper voltage (120 or 240 VAC, depending upon the wiring of the power transformer). (_ ) Turn on the Curve Tracer (until the SWEEP VOLTAGE control just clicks) and slowly turns the STEPS/FAMILY control clockwise until four to six dots appear in a diagonal row and fill the oscilloscope screen, as shown. See Figure 1-6. NOTE: Adjust the HORIZONTAL and VERTICAL SENSITIVITY controls on the oscilloscope if the dots are too widely spaced. (_ ) Use the oscilloscope horizontal and vertical positioning controls to place the first dot on the line in the lower left-hand corner as shown. (_ ) Adjust the vertical sensitivity and vertical position of the oscilloscope so each dot appears on the next higher horizontal graticule line as shown. (_ ) Adjust the horizontal sénsitivity and horizontal position so the dots appear on every other vertical graticule line as shown. (_) Make sure the first dot is still in the position shown. The Oscilloscope is now calibrated. DO NOT readjust the oscilloscope vertical and horizontal sensitivity controls. (_) Position the NORM-CAL switch to the NORM position. A single dot should appear within 1/2 division of the first dot of the calibration dots. NOTE: Condensed calibration instructions are on the rear panel of the Curve Tracer for future reference. See ETE ATELIER ITS OFFSET ADJUSTMENT Figure 1-9 Refer to Figure 1-7 (fold-out from Page 52) and turn circuit board control R84 fully counterclocksise. Refer to Figure 1-8 (fold-out from Page 52) and install the extra MPSA20 transistor in the left transistor socket as shown. Be sure the flat of the transistor is toward the rear of the cabinet. Adjust the STEPS/FAMILY control fully counterclockwise. Adjust the STEP RANGE control to .05. Adjust the SWEEP VOLTAGE control to produce a line across the bottom of the screen as shown in Figure 1-9. Turn the VERTICAL SENSITIVITY control counterclockwise until the display is near the top of the screen as shown in Figure 1-10. Adjust circuit board control R84 until the base line just becomes straight and flat. See Figure 1-11. NOTE: If you turn the control any farther than this, the base line may be distorted when you make very sensitive tests on PNP transistors and P channel FET’s. Figure 1-10 Figure 1-11 ( ) Turn the VERTICAL SENSITIVITY control to .5 and make the above adjustment again. { Gee timarrkire ] TRANSISTOR TESTS Again use the extra transistor (MPSA20, #417-801) that was supplied with your kit. NOTE: The following steps assume your oscilloscope is DC coupled. If your oscilloscope is AC coupled, you may have to make oscilloscope adjustments not listed “Set the Curve Tracer controls as follows: (See Figure 2-1 on fold-out from Page 48). in the steps. However, do not change the oscilloscope vertical and horizontal ; sensitivity controls. If necessary, again refer to ‘‘AC-Coupled Oscilloscopes’’ on Page SWEEP VOLTAGE — Fully counterclockwise and OFF. 52. HORIZONTAL SENSITIVITY — 1. (_ ) Position the dot in the lower left-hand corner of the graticule. See Figure 1-12. VERTICAL SENSITIVITY — 5. (_) Turn the SWEEP VOLTAGE control clockwise until ‘a line appears across the POLARITY — NPN. bottom of the display. Then turn the control counterclockwise until only a dot remains. , SWEEP RANGE — 0-40V. STEP SELECTOR — CURRENT. STEPS/FAMILY — Fully counterclockwise. STEP RANGE — .01. LIMITING RESISTOR — 100. LEFT-RIGHT — LEFT. _ Searicule) tt NORM-CAL — NORM. a (_ ) Turn the SWEEP VOLTAGE control only far enough clockwise to turn the DoT Curve Tracer on. LINE Figure 1-12 SSM eee Again turn the SWEEP VOLTAGE control clockwise until the bottom horizontal line is across the full length of the graticule. Turn the STEPS/FAMILY control fully clockwise. A set of nine curves plus the base line should appear. If some of the curves are off the screen, set the VERTICAL SENSITIVITY control to 10 mA/division. If they appear crowded at the bottom, set the switch to 2 mA/division. Slowly turn the STEPS/FAMILY control counterclockwise. Note that one by one, from the top down, the steps disappear until only the base line is left. Now adjust the control until three steps plus the base line appear. See Figure 1-13. If the display does not fill the screen, turn the VERTICAL SENSITIVITY switch of the Curve Tracer one step counterclockwise. Turn the LIMITING RESISTOR switch from 100 (ohms) to 50 (ohms). Note that the upper curves have increased slightly horizontally. la LOOPING UNCOMPENSATED kn on saat 3 Ld. q t —— ~ mes te ae i és abe £ Pee 5 £ ee Eudombonds Pp Pe Z BASE LINE Figure 1-13 (_) Turn the same switch to 500 (ohms). Note that the upper curves have shortened. ( ) (One or two may have disappeared entirely.) Then return the switch to 100 (ohms). Turn the HORIZONTAL SENSITIVITY switch to 2 volts/division. Note that the curves have all shortened by a factor of two. LOOPING COMPENSATED Figure 1-14 Gee HEATHEIT® ( ) Turn the HORIZONTAL SENSITIVITY switch to. .5 volts/division. Note that the curves are now twice as long as they originally were and that they may extend off the CRT. Return the HORIZONTAL SENSITIVITY switch to 1. ( ) Turn the VERTICAL SENSITIVTY control to the .5 mA/division range. (Remember where the switch was set.) One or two curves may go off the screen. (_ ) Adjust the LOOP control so the curves have a minimum of looping. See Figure 1-14. Then return the VERTICAL SENSITIVITY switch to its original position. (_ ) Turn the STEP RANGE switch to .02 mA/division and note that the steps have doubled in value. (Some steps may go off the screen.) (_) Turn the STEP RANGE switch to .005 mA/division and note that the steps are one half their original value. Then return the switch to .01 mA/division. ( ) Turn the SWEEP VOLTAGE control fully counterclockwise but not OFF. (_) Switch the SWEEP RANGE switch to 0-200 V. CAUTION: On this range dangerous voltage can be available at the ‘‘C”’ output. (_) Slowly turn the SWEEP VOLTAGE control clockwise until you obtain the same curves as before. (DO NOT turn the control further. The transistor is only rated to 40 volts.) Note that the curves have a less polished appearance. ( ) Turn the control back counterclockwise and set the SWEEP RANGE switch to 0-40 V. OBSERVATION: Use the 0-200 V range only when voltages greater than 40 are required. The 40 V range provides cleaner and more precise displays, and the exposed operating voltages are safer. (_ ) Position the dot in the upper right-hand corner of the screen. See Figure 1-15. ( ) canaen t PF “DOT i 3 tft car ae — . Ec dendewds rey 3 t ere aa i or ae ae OO ee PoE Tr Figure 1-15 Set the LIMITING RESISTOR to 1000. Set the HORIZONTAL SENSITIVITY switch to 2 volts/division. Change the POLARITY switch to PNP. Turn the STEPS/FAMILY control fully counterclockwise. Turn the SWEEP VOLTAGE control clockwise until a line appears as in Figure 1-15. This is reverse breakdown of the C to E junction. Turn the SWEEP VOLTAGE control fully counterclockwise and OFF. This completes the ‘Tests and Adjustments.” FINAL ASSEMBLY Refer to Pictorial 4-1 for the following steps. ( ( ( ( ) ) ) ) Unplug the line cord, disconnect all leads, and remove the test transistor. Carefully turn the Curve Tracer upside down. Then lower the cabinet shell into position and secure it with six #6 x 3/8" sheet metal screws and two 8-32 x 3/8” screws. Remove the protective backing from the CAUTION label and apply it to the cabinet shell as shown. ‘ Remove the protective backing from a plastic foot and press it in a corner 1/4” from the edges of the cabinet shell. Ina similar manner, install. plastic feet at the three remaining corners. Turn the Curve Tracer right side up. This completes the ‘Final Assembly” of your kit. CABINET SHELL gE 1 ? N77 “. : PLASTIC FOOT 8-32 x 3/8" g SCREW N PICTORIAL 4-1 OPERATION CONTROL FUNCTIONS Refer to Figure 2-1 (fold-out from Page 48) as you read the description of each control function. 1. PILOT LAMP (PL1) — Indicates when the Curve Tracer is plugged in and turned on. SWEEP VOLTAGE (R6, SW1) — Combination ON—OFF switch and SWEEP VOLTAGE control. Turns the unit on and off,-and sets the value of the sweep voltage at “’C” terminals. HORIZONTAL SENSITIVITY (SW6) — While the oscilloscope monitors the sweep voltage on the device under test, this switch selects one of the nine voltage ranges for a proper display. VERTICAL SENSITIVITY (SW7) — Selects one of nine current ranges so the oscilloscope can monitor the current (produced by the sweep voltage) passing through the test device. POLARITY (SW3) — Selects either NPN or PNP (N-channel or P-channel). Sweep Voltage | Current Steps Voltage Steps NPN positive positive negative PNP negative negative positive 10. 11. 12. SWEEP RANGE (SW2) — Selects sweep voltage of either 0-40 V (at up to 1 ampere maximum) or 0-200 V (at up to 200 milliamperes maximum). Always use the lower range unless more voltage is needed. STEP SELECTOR (SW9) — Selects either VOLTAGE or CURRENT steps, and the polarity of the signal supplied to the B output terminals. STEPS/FAMILY (R47) — Adjusts the number of steps from zero to nine. STEP RANGE (SW8) — Selects either current steps or voltage steps, depending on the setting of the STEP SELECTOR switch. Provides 12 values of current steps or 5 values of voltage steps. LIMITING RESISTOR (SW4) — Selects one of 11 resistors plus zero ohms. These current limiting resistors protect the device under test. Use the highest value that gives a consistent display. LEFT TRANSISTOR SOCKET — For testing small transistors out of circuit. Active when the LEFT-RIGHT switch is at LEFT. LEFT BANANA JACKS — Use these jacks with the supplied cables to test large semiconductors in and out of circuit. Active when the LEFT-RIGHT switch is at LEFT. (GegumarinxiT 13. 14. 15. 16. —= Eee LEFT-RIGHT (SW5) — Selects either the left or right socket and jacks. RIGHT BANANA JACKS — Use with the supplied cables to test large semiconductors in or out of circuit. Active when the LEFT-RIGHT switch is at RIGHT. RIGHT TRANSISTOR SOCKET — For testing small transistor out of circuit. Active when the LEFT-RIGHT switch is at RIGHT. H, G, V TERMINALS — Provide output connections to an oscilloscope. 17. 18. H connects to the horizontal input. G connects to ground. V connects to the vertical input. LOOP (R5) — Compensates for circuit capacitance to minimize looping in the display. NORM-CAL (SW10) — In the CAL position, dots resulting from a precision staircase waveform are applied to the oscilloscope for calibration. The NORM position provides normal operation. CURVE TRACER CHARACTERISTICS Because of the great versatility of this Curve Tracer, in a few instances the display may be other than ideal. These can be caused by the limitations of the device being tested, interaction between the tested device and the Curve Tracer, and, in some cases, the Curve Tracer itself. Refer to Figure 2-2 as you read the following information. A coil-like loop may occur here with sweep voltages higher than 30 volts. Higher limiting resistance will minimize this effect. Looping (double line) may occur with low sweep currents (.5 mA/div) and high sweep voltages (above 30 volts). Use the LOOP control to minimize this effect. This hump may occur with certain transistors. Use a higher value of limiting resistance to minimize the hump. A faint line at higher sweep voltages (above 30 volts) is more noticeable with less steps and can be minimized by adding more limiting resistance. E. § dnadannds ee ae AY U 4 Be Grevedaands 4 L \ $rdumbed os an 7 whe ; + : he Ow h ¢ eS ») l | ae i ——_ oe ne VA OC, ~N E / va) £ rar Zl nM . v Figure 2-2 Some reverse voltage sweep will.appear here on the .1 volts range for the low sweep range, and on the .1 volt/div through the 5 volt/div on the 200 volt sweep range. APPLICATIONS GENERAL INFORMATION PRECAUTIONS TESTING BIPOLAR TRANSISTORS To protect the device being tested, always observe the following precautions. The most common use of the Curve Tracer is to test NPN and PNP transistors. The family of curves of an NPN transistor is in a positive direction. That is, zero volts is at — Keep the SWEEP VOLTAGE below the collector breakdown level except during the left and zero current is at the bottom of the display. The curves sweep upward and the short time of a collector voltage breakdown test. Although the limiting to the right as collector voltage and current increases, and the sweep voltage is positive. resistors prevent destruction of the transistor, high internal temperatures from long periods of operation may cause the transistor to fail. The curves of a PNP transistor, however, are in the negative direction. Zero volts is at the right and zero current is at the top of the display. The curves sweep downward and — Limit the testing of power transistors without heat sinks to a few seconds — just to the left as collector voltage and current increase, and the sweep voltage is negative. long enough to make an accurate reading. Excessive temperatures in the test device may result from longer periods of operation. Start and stop the tests by Any test of an NPN transistor can be performed on a PNP and vice versa. The displays using the LEFT-RIGHT switch. are merely inverted. — Before you make a test, be sure the following controls are set as follows: Transistors can be tested for: SWEEP VOLTAGE Fully counterclockwise Current gain (DC and AC beta) SWEEP RANGE 0-40 V Collector-to-emitter breakdown LIMITING RESISTOR 5 k or higher Collector-to-base breakdown STEP RANGE .02 mA/Step or less Output admittance Saturation voltage Saturation resistance Cutoff current ‘Leakage current Linearity and distortion Temperature effects Identifying germanium or silicon Matching Sorting and substitution Return the controls to these positions after each test. This will insure that no device will be accidentally destroyed. — Completely remove power from the unit under test. The Curve Tracer supplies the complete test signal. Any additional signal or DC current may make the test inaccurate and could damage the unit. (Gg sr=arrxiT)]} 2 ee) TRANSISTOR IDENTIFICATION To test a transistor you need to know three things. 2. The type (NPN or PNP). This information can come from the circuit, schematic, manufacturer’s handbook, or from the Curve Tracer as described on Page 66. 1. The basing configuration (E, B, C, or S, G, D). Figure 2-3 shows some of the more common configurations. If the transistor type number is available, the 3. The power class. See Figure 2-3. (Signal, intermediate power, or power.) basing configuration can be found in the manufacturer’s handbook. Also, a schematic may provide this information. SIGNAL TRANSISTORS POWER A _\ C_-) ( HEAT SINK =) coy) a a HEAT SINK ECB ECB @ am a i 2h ywe [lL or Ps ZIV AR INTERMEDIATE POWER HEAT, SINK HEAT SINK Figure 2-3 COLLECTOR (MOUNTING FLANGE) COLLECTOR (MOUNTING FLANGE) Swe SEE ATHEIT® INITIAL DISPLAY To obtain an initial display, set the Curve Tracer controls as shown below. Note that the switches marked with an asterisk are always in these positions for transistor tests. Refer to Table 1 and make other control settings according to the power rating of the transistor. Also, if the oscilloscope is not connected and calibrated, see ‘Oscilloscope Calibration’ on Page 54. SWEEP VOLTAGE — Fully counterclockwise and off. HORIZONTAL SENSITIVITY — See Table 1. VERTICAL SENSITIVITY — See Table 1. POLARITY — Set for type of transistor. SWEEP RANGE — 0-40 Vv. STEPS/FAMILY — Fully clockwise. *STEP SELECTOR — Current. STEP RANGE — See Table 1. LIMITING RESISTOR — See Table 1. LEFT-RIGHT — Left. LOOP — Fully clockwise. *NORM-CAL — Norm. Base HORIZONTAL VERTICAL LIMITING SWEEP Step SENSITIVITY SENSITIVITY RESISTOR | RANGE SIGNAL .002 1 Vidiv. 5 mA/div. 5k 0-40 V INTERMEDIATE POWER .02 1 V/div. 5 mA/div. 500 0-40 V POWER 2 1 Vidiv. 50 mA/div. 50 0-40 V TABLE 1 Turn the SWEEP VOLTAGE control clockwise only far enough to turn the unit (_) Set the LEFT-RIGHT switch to RIGHT. on. Connect the transistor to be tested to the right socket, or to the E, B, C terminals with test leads. | ‘PNP ee) J cd ebnnnd, pose Sebemduund, Beoefooo$. ss Pte eee ee eee ee ett tt ad £ \ NPN x . DON'T KNOW TYPE Figure 2-4 () If the transistor is an NPN, place the dot in the lower left-hand corner of the screen. If it is a PNP, place it in the upper right-hand corner of the screen. If you don’t know if it is NPN or PNP, place the dot in the middle of the screen as shown in Figure 2-4. NOTE: Perform the following numbered steps only if you don’t know if the transistor is an NPN or PNP. whe Fa awd cy Senndeenbened, Bdefarabeeafunflmdmnfered Saban ia ae we i deans pe ee ee ee LO i a a a es Sa a a ae a) PEP Ep ry eT Te T yore Ge UG Figure 2-5 ae ee ee Prey Jen Gwecboond Pet fae ae) con a ae ae we rans Pe §. Srenhadh $2 FE Badenbrend: Pree Figure 2-6 Figure 2-7 Slowly turn up the SWEEP VOLTAGE control. If the transistor is an NPN, curves will appear as shown in Figure 2-5. If it is a PNP, no curves will appear and breakdown, as shown in Figure 2-6, may appear. If this happens, switch the Polarity control to PNP. Then curves as shown in Figure 2-7 should appear. Refer again to Figure 2-4, turn the SWEEP VOLTAGE control fully counter- clockwise, and place the dot in the appropriate corner of the screen for NPN or PNP. NPN (Gea rrmarrrrrs] lS eh) PNP Figure 2-8 Figure 2-9 Figures 2-8 and 2-9 show typical displays of NPN and PNP transistors. They are identical — only inverted. NOTE: If some curves go off the screen, switch the VERTICAL SENSITIVITY control to the next higher range (clockwise). Also, you may have to lower the LIMITING RESISTOR value. If the curves are to close together, select a more sensitive current range. Table 2 gives ranges of operating parameters for transistors with different power ratings. Use Table 1 as a starting point to ensure that the device will be operated within its specifications. Always be cautious when you use ranges listed in Table 2 so that the device ratings are not exceeded. BASE CURRENT RANGE COLLECTOR CURRENT RANGE VOLTAGE RANGE SIGNAL (Audio, RF, IF, etc.) .002 through .1 mA/step -5 through 5 mA/div. STAY BELOW DEVICE BREAKDOWN INTERMEDIATE POWER STAY BELOW (Audio, Switching) ‘| .02 through 1 mA/step 2 mA through 50 mA/div. DEVICE BREAKDOWN POWER STAY BELOW (Audio, Output, .2 through 10 mA/step 20 mA through 200 mA/div. DEVICE BREAKDOWN Regulator) TABLE 2 fae PIE ATHEITS MEASUREMENTS In-Circuit Tests — Many times these can only be made by comparing results with those known to be proper: If no curves can be obtained at all, remove the device from the circuit and then test the device. Matching Transistors — It is often desirable to match transistors for gain, linearity, saturation, Output admittance, etc. Use the LEFT-RIGHT switch to compare the curves. Matched devices have identical curves. Sorting Transistors — To sort transistors, use the oscilloscope controls and place the CRT dot (with no input signal) in the center of the screen. Then NPN transistors will produce curves in the upper right-hand quadrant of the screen and PNP transistors will produce curves in the lower left-hand quadrant of the screen as you flip the NPN-PNP switch back and forth. Integrated Circuits — Integrated circuits are often several transistors, diodes, etc. packaged together. These IC’s may be tested if the internal devices can be identified and isolated to specific terminals of the IC. Note, however, that other circuit elements may produce loops in the curves, or other variations, of the display. The following are examples of typical measurements and the control settings under which they were performed. Many of these use the extra MPSA20 (#417-801) transistor supplied with your kit; the control settings may vary widely for other devices. NOTES: 1. All of these tests, unless they are described otherwise, were made with the NORM-CAL switch in the NORM position, the LOOP control adjusted for minimum looping, the LEFT-RIGHT switch in the LEFT position, and the SWEEP VOLTAGE control adjusted clockwise for a proper display. 2. If a transistor is open, only the base line will appear on the display. If the transistor is shorted, there will be a vertical line as in Figure 3-2 but there will be no base line. Proceed to the heading of the test you are interested in. zs) SATURATION VOLTAGE [VE (sat)! MPSA20: HORIZONTAL SENSITIVITY -1 volts/Div. VERTICAL SENSITIVITY 2 mA/Div. POLARITY NPN STEPS/FAMILY 5 steps STEP RANGE .01 mA/Step LIMITING RESISTOR 0 12 SATURATION 1 REA / ~ 0 I “LINEAR / / se AREA a 5 6 7 8B Vc (VOLTS) Figure 3-1 The collector saturation region of a transistor is that portion of the family of curves in the area of low collector voltage and current below the knee of each curve. The knee of each curve occurs at approximately the same collector voltage (from .18 to .32 in Figure 3-1). Collector voltage above the knee has little effect on collector current; the base current controls collector current in this area. MPSA20: VceE (sat) = 0-25 VDC (MAX) @ Ig = 10 mA and Ip = 1 mA. HORIZONTAL SENSITIVITY VERTICAL SENSITIVITY .1 Volts/Div. 2 mA/Div. POLARITY NPN STEPS/FAMILY 1 Step STEP RANGE 1 mA/Step LIMITING RESISTOR 0 —=—— CURRENT LIMITING BY CURVE TRACER 12 10 (mA) Voglsat) = 04 VOLT AT SPECIFIED 4 ! LOMA.OF Le x | ae 2 | adios I SPECIFIED V.-(sat) max. (0) 1 2 3 A 5 6 7 8 9 +10 Vc Figure 3-2 Transistor data sheets specify VCE(sat) as a maximum voltage at a given base current . and collector current. In Figure 3-2 this value is .04 volt. Saturation resistance, ce(sat), can be calculated, if desired, by the Ve ns formula "ce (sat) “7 for a given value of base current in the saturation ‘region. In c 04V 40mvV Figure 3-2, tce(sat) “TOmA~ TOmA~ 4 & LEAKAGE CURRENT (IcEo) and (Ices) The leakage current is proportional to the collector-to-emitter voltage and becomes HORIZONTAL SENSITIVITY 5 Volts/Div. greatest as the breakdown voltage is approached. For a good transistor, IcEo i is always greater than IcgEs. VERTICAL SENSITIVITY 5 mA/Div. SPER ANILY iN NOTE: Silicon transistors typically have leakage currents in the nanoampere region _ and will not display any leakage on the Curve Tracer. Germanium transistors are /much STEP RANGE Any position more likely to show measurable leakage. LIMITING RESISTOR 5k IcEQ is the collector to emitter leakage current that flows when the base is open (not ‘connected). Icgs is the collector to emitter leakage current that flows when the base is shorted to the emitter. 3.0,- IcEO — Do not connect the transistor base lead to the Curve Tracer. 2.5 IcEs — Connect both the transistor base lead and emitter lead to the E connector of the transistor socket. See below. 20 Potted sabia GAahe GRGAAGAENG GARE SAEED UHRA 1.0 LEAKAGE (IF ANY) (0) 5 10 15 20 25 30 35 40 40 50 Ve Figure 3-3 f <—— Re HEATHEIT®| — a BREAKDOWN VOLTAGE MPSA20: Minimum 40 volts at 1 mA of lo HORIZONTAL SENSITIVITY 5 volts/Div. VERTICAL SENSITIVITY 2 mA/Div. POLARITY NPN STEPS/FAMILY 5 Steps STEP RANGE .005 mA/Step LIMITING RESISTOR 5k The breakdown voltage is where the collector current becomes independent of the base current and rises sharply until limited by the Curve Tracer. If it were not for this limiting, the transistor would be destroyed. Keep the test short so the transistor is not damaged by too much heat. Increase the sweep voltage until the collector breakdown point is reached. Most transistors can be tested for breakdown because of the high voltage capability _ (200 volts) of the Curve Tracer. 12 “— BREAKDOWN 10 an LINEAR - AREA x X Be 8 \ Tv To 6 RH ete: (mA) shew 4 a xz SPECIFICATION 2 wan 0 5 0 8 20. 25 Vc (VOLTS) Figure 3-4 OUTPUT ADMITTANCE (hoe) MPSA20: . HORIZONTAL SENSITIVITY 5 volts/Div. VERTICAL SENSITIVITY 2 mA/Div. POLARITY NPN STEPS/FAMILY 5 Steps STEP RANGE .005 mA/Step LIMITING RESISTOR 5k The output admittance of a transistor is the change in collector current (Al,) that results from a specific change in collector voltage (AV,) at a constant base current. Admittance is measured in ~tmhos and its “h’ parameter in the common emitter Al Al A configuration is hog = a a -ome 32 umhos. c c The output impedance of the transistor (collector resistance) is the reciprocal of its output admittance and is measured in ohms. To calculate it, transpose the current and voltage values used to determine the admittance. Output impedance - ve - 25 __ 31,250 ohms EE Ng BMA 12 a 10 “- 8 ——" cs areas RRMA RAARARBAAS o>" onan Ree naee BARRA CORT t 2 ] 4 ae c > 4 2 + — ) 5 10 6«6 150i 20—é—«a Hs 380 35 40 45 £50 Vc A\Vc= 25V (VOLTS) Figure 3-5 SSM eee DC BETA (hre) MPSA20: 40-400, |, = 5 mA, V, = 10V HORIZONTAL SENSITIVITY 1 Volt/Div. VERTICAL SENSITIVITY 5 mA/Div. POLARITY NPN STEPS/FAMILY 3 Steps STEP RANGE .05 mA/Step LIMITING RESISTOR. 100 Beta (8) is the ratio of collector current to base current and is equal to current gain. That is, for a given base current, a proportionally larger collector current is produced. DC beta is dependent upon what collector voltage and current points are picked. Even at specific values, DC beta can vary greatly in the same type device. DC Beta is found by the formula: I DC beta =£ IB Therefore, the above example pioduces a beta of: Io 20 mA | B=", B= 4mA 8= 200 25 lA + se oc deasuseues | + c720mMA, Ve=4V 20 Ip =.1mA “ re 15 PYRE EE [ : 0 1 2 3 4 5 6 7 8 9 10 Ve (VOLTS) Figure 3-6 DC beta is indicated by capital FE in the term “he,,” while AC beta is indicated by lower case fe in the term “h,,.” | ne MPSA20: 25 \ ae HORIZONTAL SENSITIVITY 1 Volt/Div. 20 Iprylma VERTICAL SENSITIVITY 5 mA/Div. —_— + POLARITY NPN Ic |, + ~\ STEPS/FAMILY 3 Steps (mA) fa eee EE EEE EEE EPH SAH HEH STEP RANGE .05 mA/Step las osmat LIMITING RESISTOR 100 10 - AC beta, or gain, is the ratio of change in collector current to the change in base 5 a: current. This measurement is more useful because it is taken under actual operating | + conditions and performance can be more precisely predicted. re) 1 2 3 4 5 6 7 8 9 10 If the transistor data sheet is available, beta should be measured at the approximate Vee (VOLTS) collector current and voltage specified. If not, the STEP RANGE is usually adjusted for a display of the most evenly and widely spaced curves. . Figure 3-7 Gain is usually higher in the normal operating region of the transistor and is lower at collector currents above or below this region. Calculate AC beta as follows: 3. Then AC beta = Ale at Vce of 4 volts Alp 1. Measure the difference in collector current (A |.) between two curves at the same collector voltage. B= 9mA .05 mA 2. Note the change in base current (A Ih) from the STEP RANGE switch. (.05 mA in this case.) B= 180 eee arene] eaE=zs LINEARITY AND GENERAL DISPLAY-LOW I, LINEARITY AND GENERAL DISPLAY—HIGH I, MPSA20: MPSA20: To maximum of 100 mA of |, HORIZONTAL SENSITIVITY 2 Volts/Div. HORIZONTAL SENSITIVITY 1 Volt/Div. VERTICAL SENSITIVITY ° 2mA/Div, VERTICAL SENSITIVITY 20 mA/Div. POLARITY NPN POLARITY NPN STEPS/FAMILY 9 Steps SER Ae. er STEP RANGE .005 mA/Step y MITING RESISTOR <0. tep LIMITING RESISTOR 1k ITIN . , Nonlinearity increases with an increase in collector current. (Note the closer spacing of Linearity is a measure of the transistor’s ability to amplify, in exact proportion, a the upper curves.) signal that appears at its base. , The step generator in the Curve Tracer produces precise steps. Therefore, if the device being tested is perfect, the spacing between curves will be constant — similar to the curves in Figure 3-8. These curves can be used to check both gain and linearity. 120 Linearity is usually better with a low collector current. ; 100 ; ss _— — 80 ai 12; - Te 60 Voy 10 | ae . (mA) | : 40 8 ae 20 6 bibs fafefebebeeped [ (¢) 4 1 2 3 4 5 6 7 8 9 10 £ (VOLTS) (mA) oa . ~. Figure 3-9 oO 2 4 6 8 10 12 14 16 18 20 (VOLTS) Figure 3-8 (age arearry SSM To measure nonlinearity: NONLINEARITY 1. Plot an imaginary line along the ends of the curves. This is the ‘test load line.” MPSA20: 2. Plot an “operating load line” in parallel with the test load line but intersecting HORIZONTAL SENSITIVITY 1 Volt/Div. the zero IC line at the desired operating Ve for the transistor VERTICAL SENSITIVITY 5 mA/Div. 3. Measure and compare the changes in collector current (A |,) between the curves POLARITY NPN on the operating load line. If the changes are the same, the transistor is linear at STEPS/FAMILY 3 Steps this p