6.002 Demo# 06 ( Load set up Demo#06.set) S/SR/SCS models Agarwal Fall 00 Lecture 6 (and 8) Oscilloscope Setup CH V/DIV OFFSET MODE FUNC MATH VERTICAL HORIZONTAL Horizontal: 2 m Acquisition: AUTO AUTO 4 Trigger: CH1 Waveform Generator Setup Power Supply Setup UNIT WAVE AMP OFFSET FREQ +6 +25 -25 OUTPUT FG1 DCV 0 2 & 5 V 1 k Hi Z OFF6.002 Demo# 06 ( Load set up Demo#06.set) S/SR/SCS models Agarwal Fall 00 Lecture 6 (and 8) Purpose: This demo illustrates the various models of the MOSFET, namely the S, SR, and SCS models. The models are displayed on the scope by plotting the current iD (taken as a voltage across a load resistor) versus the voltage vDS, with a sinusoidal drive on VS to display a line rather than simply a point. The S and SR models are shown by switching vGS between voltages above (ON state) and below (OFF state) the MOSFET threshold voltage. The SCS model is shown in a similar manner, by incrementally increasing vGS from just below vT to some amount above it. This shows the saturation (current source) region of the MOSFET not visible when larger values of vGS are used. Steps: 1. To show the switch model, vIN is set to a large value, and switched on and off. The i-v characteristic as seen from the drain to the source is shown on the scope. The curve looks like an open circuit (horizontal line) and a short circuit (vertical line) accordingly. 2. To show the switch-resistor model, vIN is set to a slightly smaller value, and switched on and off. The i-v characteristic as seen from the drain to the source is shown on the scope. The curve looks like an open circuit (horizontal line) and a resistor (sloped line) accordingly. 3. To show the switch-current source model, vIN is set just below vT and increased incrementally, to show a family of curves. S model SR model SCS model Description: MOSFET Switch ( S ) ; switch resistor ( SR ) ; Switch Current Source (SCS) ; models 1) Set FG2 @ High Z mode, frequency @ 500 HZ Sine, Amp @ 3 v p-p, Offset @ 1.5 v p-p 2) Set FG1 @ High Z mode ( DC offset only ) press DC offset button and hold it until you hear the click! a) To show S model, set FG1 dc offset to 5 v, ( NOT MORE THAN 5 V IT WILL DAMAGE THE FET) turn the switch (S1) on the pc board to FG1 to show VGS>VT and off to show VGS<VT. See Fg1 pictorial graph! b) To show SR model, set FG1 dc offset to 2.6 v, turn the switch on the pc board to FG1 to show VGS>VT and off to show VGS<VT. See Fg1 pictorial graph! c) To show SCS model, making various curves, do the following: The switch on the pc board should be set on FG1 ON, roll FG1 dc offset voltage between 2 &2.4 v by tenths ( i.e. 2.0, 2.1, ….2.4). See Fg1 pictorial graph! *Note: See below the sequence of button to change from 50 Ohm termination to High Z mode! Cite as: Anant Agarwal and Jeffrey Lang, course materials for 6.002 Circuits and Electronics, Spring 2007. MIT OpenCourseWare (http://ocw.mit.edu/), Massachusetts Institute of Technology. Downloaded on [DD Month YYYY].Oscilloscope Setup CH V/DIV OFFSET MODE FUNC MATH VERTICAL HORIZONTAL 1 off 1 0 DC off CH1− CH2 2 off 1 0 DC off F1 ÷ 500 m 3 off 1 -1.0 DC on F2 vs CH2 1 2 500mv 999 mv 4 off 2 6.0 DC off CH2-CH3 Horizontal: 2 m Acquisition: AUTO AUTO 4 Trigger: CH1 Waveform Generator Setup Power Supply Setup UNIT WAVE AMP OFFSET FREQ +6 +25 -25 OUTPUT FG1 DCV 0 2 & 5 V 1 k Hi Z OFF FG2 SIN 3 1.5 500 HZ Hi Z Trigger: INT, INT • See the sequence of buttons to be pressed > >0 > 0.4v v < High > 50 Ohm Cite as: Anant Agarwal and Jeffrey Lang, course materials for 6.002 Circuits and Electronics, Spring 2007. MIT OpenCourseWare (http://ocw.mit.edu/), Massachusetts Institute of Technology. Downloaded on [DD Month YYYY].7 100 Ohm CH2 2N70005FG2FG1 (14)*(2)(2)Fg1 VGS > VtVGS < VT VGS > VT VGS<VTIDID VDS IDVDSS/SR/SCSMODELS*Note # of pinson the PCboard and BNCconnectorsS117 (17) * (2) *(2) *BNC ( ) Pins14 S1 ( 7 ) * (5) * Cite as: Anant Agarwal and Jeffrey Lang, course materials for 6.002 Circuits and Electronics, Spring 2007. MIT OpenCourseWare (http://ocw.mit.edu/), Massachusetts Institute of Technology. Downloaded on [DD Month
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