Lab6 Report Instructions

• Preparation:
  • 1- Use DC sweep in PSpice to get VI curve for JFET using DC voltage sources for drain-source (sweep from negative to positive values) and gate-source (sweep from 0 to negative values), no resistor is needed. Use the values in figure 6-1 for start.
  • 2- Compute resistance vales for obtained straight lines (VI curves). Use R = 1/slope. Label the calculated resistance and gate-source voltage for each line.
  • 3- Select the most vertical line (highest slope value) to be RJFET ON state, and the most horizontal line (slope ~ 0) to be RJFET OFF state. Select the gate-source voltages associated to those states to define voltage limits for control signal (square pulse).
  • 4- Build circuit in figure 6-3 with R1 10 times larger RJFET  ON state, use Vpulse (1 Khz, dc 50%) as control signal with levels from part 3, use Vsin (10 Khz) as input signal with amplitude for drain-source voltage from part 1, run transient analysis, plot output signal for 2 complete periods.
  • 5- Repeat part 4 with Vpulse (100 Khz, dc 10%) control signal.

• Procedure:
  • 1- Get VI curve for JFET using FET_Resistance.vi and Procedure Supplement sheet provided by TA, record drain-source voltage values for straight lines obtained.
  • 2- Compute resistance vales for obtained straight lines (VI curves). Use R = 1/slope. Label the calculated resistance and gate-source voltage for each line.
  • 3- Select the most vertical line (highest slope value) to be RJFET ON state, and the most horizontal line (slope ~ 0) to be RJFET OFF state. Select the gate-source voltages associated to those states to define voltage limits for control signal (square pulse).
  • 4- Build circuit in figure 6-3 with R1 10 times larger RJFET  ON state, use a DC source as control signal for gate-source (use selected values in part 3 for ON & OFF states), use the function generator  (10 Khz) as input signal with amplitudes pp = 50 mV for drain-source voltage, capture input and output signals with scopegrab.vi, and register pp voltage values for input and output.
  • 5- Repeat part 4 for input signal with amplitudes pp = 70 mV for drain-source voltage.
  • 6- Repeat part 4 for input signal with amplitudes pp = 100 mV for drain-source voltage.

• Analysis:
  • Plot Vout vs.Vin for ON state for all 3 input signal values, explain and comment on results.
  • Plot Vout vs.Vin for OFF state for all 3 input signal values, explain and comment on results.

   

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