EL  250
Advanced Analog Circuits
Lab #3: Common Source JFET Amplifier
Andrew Buettner
Objective
The objective of this lab is to determine the characteristics of a JFET, then to use that JFET in an audio amplifier to test it's operation by measuring the output and input voltages to calculate the theoretical and actual gain for a comparison.
Equipment Used
No equipment necessary for this experiment. All data taken from computer simulations.
Procedure
I: Part A
1) Assemble the following circuit:
2) Run the simulation ensuring that the results are similar
3) Set V_{GS} to .5V and record the results
II: Part B
1) Using the values obtained from part A to determine the V_{P} for the theoretical JFET
2) Use the value calculated for V_{P} to calculate I_{DSS}
3) Using V_{GS} and the calculated I_{DSS} calculate I_{D}
III: Part C
1) Assemble the following circuit:
2) Determine ID, gm, the voltage gain, and the voltage output
IV: Part D
1) Load CSJFAMP.CKT in CircuitMaker©
2) Run the simulation and determine V_{out}
3) Compare the result with that of part C
Data
1) Table 1: Results from Part A
V_{GS} 
V_{RD} 
I_{D} 

1V 
1.832V 
1.832mA 
.5V 
8.362V 
8.362mA 
2) Table 2: Results from Part B
V_{GS} 
V_{P} 
I_{DSS} 
I_{D} 

1V 
1.44V 
19.62mA 
1.83mA 
.5V 
1.44V 
19.62mA 
8.36mA 
3) Table 3: Results from Part C
V_{OUT} 
I_{D} 
gm 
A_{V} 

8.232V 
1.968mA 
90.6mS 
205.8 
4) Table 4: Comparison between Part C and Part D results

Part C: 
Part D: 
% error: 

V_{OUT} 
8.232V 
8.050V 
2.211% 
5) Diagram 1: Schematic, 1 Enlarged View
6) Diagram 2: Schematic 2, Enlarged View
Conclusions
From this lab, it is shown how to use a JFET in an audio amplifier circuit and perform a small signal analysis. I would like to comment that the final voltage on the simulation may not be accurate as the voltmeter and oscilloscope were not giving accurate readings, either that or I was not reading them correctly as this is the first time I've ever used circuit maker. I was able to overcome all other problems as I feel that my calculations are fairly accurate (< 3% error from simulation.)
Attachments
1) Original Lab Handout
2) Original Lab Data
3) Calculations