Unipolar transistors measurement

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1 Unipolar transistors measurement 1. Important notice for students: Transistor s circuits works with frequency till hundredths MHz. For these frequency the interconnecting wires creates significant unwanted inductive and capacitive bindings, which cause oscillation of circuits. Oscillations are near limit values of V and I and disallow measurement of static characteristic, setting working points of amplifiers etc. Better, than using any RC filters is using suitable wiring. Solution is to prevent the rise of inductive loops. There exists simple rule. Each current have to return along the same way where to go there. This can be simply realised, when we twist connecting leads to measurement devices as A-meters V-meter. Powering of measuring kit uses flat double wire cable and scope probes uses coaxial cable connection. Better, than twisted pair wires, is coaxial cable, worse is flat double cable. Free non-arranged connection, realised according scheme, without its understanding is in communication, digital and power converter electronic functional nonsense. You should ensure that the area between free ends of connection leads must be minimal. Right example of connection of kit with transistor measurement is on following figure. 2. Important notice for students and teachers: Please, don t forget switch off multi-meters after measurement battery cells are expensive.

2 1. Measurement of static characteristics of Unipolar transistor N-MOS - type BS 107 or J-FET - type 2SK170 Task: 1) Measure dependence i C = f(u C, u G ) for given MOS or J FET transistor (N-channel). Plot the graphs. 2) Find transconductance (mutual conductance) y 21 and output admitance y 22 of transistor in working point according teachers instructions: v G =... V, v C =... (individual, as per teacher) i C i C y21 for vc 0 y22 for vg 0 v G v k Connection diagram for measurement output characteristic of N-MOS transistor. Table example for measured values of transistor characteristic: for BS107 select u g near +2V for 2SK170 select u g near +0,5V in such range, to be for v C = 10V i C in steps of 2mA from 0 to max 16 ma. u g V 0,5 1 2 u C V 3 i k ma BE CAREFULL! DO NOT OVERLOAD THE LIMIT HEAT DISSIPATION P Cmax = U C.I C

3 Parameter transistor limits: These valuet mustn t be in any case exceeded! BS107 (unip. transistor MOS-FET, N-channel): U C max = 200 V, I C max = 250 ma, P C max = 0,35 W 2SK170 (unip. transistor J-FET, N-channel): U C max = 60 V, I C max = 150 ma, P C max = 0,35 W Maximal power dissipation P Cmax = U C.I C in any measured point. During measurement limit P C <= 0,25W, e.g. I K <=20mA for V CE = 12V BS107, 2SK 170 Bottom terminal view D... drain... C collector G... gate... G gate S... source... E emitter 2. Measurement and calculation of transistor amplifier with N-MOS transistor. Connection diagram:

4 Measurement task: For all of A, B, C circuits (or according teacher instructions) do: 1) Connect given R K and R E into the kit and connect power supply. 2) Using potentiometer P working point, given by voltage between collector and emitter of transistor e.g. U CO = 5V (or U CO = 6V or U CO = 4V, according teachers instructions for all connections). In advance by calculation find current I CO and dissipation power P Cmax = U Co. I Co and verify, that it is less than 0,25 W. 3) Next to setting working point connect on input voltage v 1 of rectangular waveform of frequency cca. 1 khz from internal kit generator. Peak to peak voltage on input v 1 and voltage on output v 2 read using scope. Calculate amplifying coefficient A u using ratio v 2 and v 1 v2 A v v1 Tasks for calculations: For all of A, B, C connection do: 1) For given values of U A, R C, R E plot into diagram: Load line p, Dynamic transfer characteristic i C = f(v G ) Voltage transfer characteristic v C = g(v G ) 2) Plot into diagram working point P for given value of U CO (e.g. U CO = 5 V). And find : a) static values of v co, u go b) parameters y 21, y 22. c) dynamic transconductance S d d) Voltage amplifying coefficient A u 3) By calculations verify S d and A v using y 21, y 22. 4) Results of measurement and calculation compare and evaluate.

5 Possible combinations of parts (teacher can set another combination) U A = 12V (according power source on working place) connection A connection B connection C verse I II III IV I II III IV I II III IV R C [ ] 1k 2k2 1k 2k2 1k 2k2 1k 2k R E [ ] k 1k 2k2 1k 2k2 U C0 [V] Measurement of inverter Measure dependence v 2 = f (v 1 ) - transfer characteristic of inverter for BS107 and 2SK170 if enough time I II III IV R C [ ] 1k 2k2 1k 2k2 R 1 [ ] 10k M1 10k M1 R 1 [ ] k M1



8 Static characteristic for 2SK J-FET: