Variable Gain Amplifier

1
Variable Gain Amplifier

• Team Members
• Pamela Danner
• Daniel Jackson
• George Varghese
• Advisor
• Dr. Bredeson

2
Presentation Overview

• Project overview
• PSpice design
• Implementation
• Final testing
• Gantt chart
• Budget
• Conclusions

3
Project Overview

• Design a variable gain instrumentation amplifier
  using commonly available op amps
• Input
• Function generator
• Output
• Amplified signal
• Oscilloscope
• Required Features
• Gain Control
• J2N4391 JFET
• DC to 10kHz signal amplification
• TL082 op amp

4
Schematic
5
Schematic Peak Output
6
Circuit
7
50 mV 10 Hz Input
8
Amplified Output 10 Hz
9
50 mV 50 Hz Input
10
50 Hz Input Distortion
11
Amplifier Output 50 Hz
12
50 Hz Output Distortion
13
50 mV 100 Hz Input
14
100 Hz Input Distortion
15
Amplified Output 100 Hz
16
100 Hz Output Distortion
17
146mV 1 kHz Input
18
1 kHz Input Distortion
19
High Gain 1 kHz Output
20
1 kHz Output Distortion
21
50 mV 10 kHz Input
22
10 kHz Input Distortion
23
2.37 V 10 kHz Output
24
10 kHz Output Distortion
25
50 mV 20 kHz Input
26
2.31 V 20kHz Output
27
20 kHz Output Distortion
28
Distortion w/ Balancing Resist.
29
Distortion w/o Balancing Resist.
30
W/ DC Capacitors
31
W/O DC Capacitors
32
Upper 3-dB Point
33
(No Transcript)
34
Budget Overview
35
Equipment Budget
36
Labor Budget
37
Parts Budget
38
Expected Budget
39
Final Expenditures
40
Final Thoughts

• A lower noise function generator would have
  allowed for more accurate testing of THD as would
  a Spectrum Analyzer

41
References

• Dr. Bredeson, Dr. Neuber, Scott McClure
• http//www.allaboutcircits.com
• http//www.orcadpcb.com
• "Op-Amp Handbook" by Fredrick W. Hughes, 1993
• "Amplifier Applications of Op Amps" by Jerald
  Graeme, 1999

42
Any Questions?

• ?