Undergraduate student projects on determining demodulation RFI statistics for operational amplifiers

A team of five undergraduate Electrical Engineering students under the supervision of a graduate student have measured RFI effects in an inverting operational amplifier (op amp) circuit with a voltage gain equal to ten for two sets of input and feedback resistor values. For the first case, the input resistor R1 is 10 k Omega , and the feedback resistor R2 is 100 k Omega . For the second case, R1 is 0.1 M Omega and R2 is 1 M Omega . Measurements were made with and without the RFI suppression capacitor C2=27 pF shunting R2. Each student was assigned 25 to 30 op amps of one type. The five op amp types tested and their input transistor type are the following: (1) 741 (bipolar NPN); (2) LM10 (bipolar PNP); (3) LF355 (JFET); (4) CA081 (MOSFET); (5) OP27 (NPN bipolar).<
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