Keithley 7015-S Instruction Manual

Contents

Keithley 7015-S Instruction Manual Manual pdf 56 page image

Operation4-104.4.3 Transistor current gain testingThe DC or static common-emitter current gain of a transistorcan be determined by biasing the transistor for a specific val-ue of base current, IB, and then measuring the collector cur-rent, IC. The DC common-emitter current gain, β, of thetransistor is then determined as follows:Figure 4-7 shows the test configuration and equivalent circuitfor the current gain test. The Model 224 Current Source isused to source the base current, IB. The Model 230 VoltageSource supplies the collector-emitter voltage, VCE, and thecollector current, IC, is measured by the Model 2001 Multi-meter. Switching among the transistors being tested is, ofcourse, performed by the Model 7015 multiplexer card.In order to perform the current gain test, the voltage sourceis first set to the desired value of VCE. The current source isthen set to a base current value that will result in the desiredvalue of IC as measured by the DMM. The current gain canthen be calculated as outlined above.Because of the 130Ω (typical) channel resistance of theModel 7015, collector current values should be kept as smallas possible to minimize voltage drops across the relay con-tacts. For example, a 1mA collector current will result in anominal 0.1 to 0.2V voltage drop across the relay contacts.4.4.4 Testing with matrix cardsThe Model 7015 can be added to a matrix switching systemto enhance the test capabilities of that system. The followingparagraphs discuss an overall multiplexer/matrix switchingsystem.Multiplexer and matrix card connectionsFigure 4-8 shows a typical system using Model 7012 and7015 cards together. In this instance, the multiplexer card isconfigured as four 1 × 10 multiplexers. Note that rows of thematrix card are connected to the banks of the multiplexercard through the analog backplane of the mainframe; no ex-ternal wiring is necessary to connect the two cards together.In this application, the DUTs are connected to the bank in-puts on the multiplexer card, allowing a large number ofDUTs to be switched through the matrix card. Also, the in-struments are connected to the columns on the matrix card.This particular configuration is best suited for applicationsrequiring a large number of DUTs to be connected to severalinstruments. In other cases, the test configuration may callfor a large number of instruments and few DUTs. In thosesituations, the instruments would be connected to the multi-plexer inputs, and the DUTs would be connected to the col-umns.β I CI B-----=Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com