Electronic Devices and Circuits – EET2222

 

 

Lab 9 – JFET Amplifier

 

 

References:

·        Floyd, Thomas L., Electronic Devices, 7th Ed., Chapter 7 and
      Sections 8-1 and 8-2.

 

·        Fairchild Semiconductor Data Sheet for 2N5484 / 2N5485 / 2N5486
      N-Channel RF Amplifier

 

 

 

Objectives:

After completing this experiment, you will be able to:

 

·        Demonstrate the operation and characteristics of a self-biased common-source amplifier.

 

 

 

Procedure:

 

1.      Determine the values of VGS(off), IDSS and gm0 of the JFET you will be using for this lab.  (Hint: use the techniques from Lab 8 to find VGS(off) and IDSS, then use Equation 7-3 to determine gm0.)

 

2.      Construct the circuit in Figure 1 using a 2N5486 JFET.  Measure the quiescent drain current ID, gate-to-source voltage VGS and the drain voltage VD.  Use Equation 8-5 to determine if the measured value of ID is consistent with the calculated value (Hint: calculate the right side of Equation 8.5 and see how close it matches the left side).

 

3.      Calculate the JFET’s transconductance gm at the quiescent point.  (Hint: use Equation 7-2).

 

4.      Calculate the voltage gain and expected Vout of the circuit (Hint: use Equation 8-6 for the AC portion of Vout).

 

5.      Apply Vin and measure Vout.  Compare the measured and calculated values of Vout.

 

6.      Use the Agilent 54621A Oscilloscope to capture the display of Vin and Vout.  Print the image, label appropriately, and attach to your lab report.  Consult the User’s Guide for how to accomplish this.

 

The report for this lab is due at the end of the lab period.  Please use the green engineering paper.  Remember to show your calculations!

 

 

 

Figure 1: