Comparison of demodulation RFI in inverting operational amplifier circuits of the same gain with different input and feedback resistor values

Author

Ghadamabadi, Hamid ; Whalen, James ; Coslick, R. ; Hung, C. ; Johnson, T. ; Sitzman, W. ; Stevens, J.

Author_Institution

Dept. of Electr. & Comput. Eng., State Univ. of New York at Buffalo, NY, USA

fYear

1990

fDate

21-23 Aug 1990

Firstpage

145

Lastpage

152

Abstract

The magnitude of the voltage gain for each circuit is equal to 10. The two op amp circuits are identical with the exception of the values for the input and feedback resistors. In one circuit the value of the input resistor is 10 kΩ, and the value of the feedback resistor is 100 kΩ. For the other circuit, corresponding values for input and feedback resistors are 100 kΩ and 1 MΩ, 50% amplitude modulated (AM) signals were injected into the op amp signal input terminal to produce an undesired demodulated response at the 1 kHz AM-frequency. The RF frequency was varied over the range 0.1 to 400 MHz. Four op amp types were tested. Experimental results show that increasing the values of input and feedback resistors improves the RFI (radio frequency interference) immunity of the inverting op amp circuit. The improvement is caused by the parasitic capacitances of input and feedback resistors

Keywords

demodulation; interference suppression; operational amplifiers; radiofrequency interference; 0.1 to 400 MHz; 1 Mohm; 1 kHz; 10 kohm; 100 kohm; AM-frequency; RFI immunity; amplitude modulated signals; demodulation RFI; feedback resistors; input resistor; input terminal; inverting operational amplifier; op amp circuits; radio frequency interference; voltage gain; Amplitude modulation; Circuit testing; Demodulation; Feedback circuits; Operational amplifiers; Parasitic capacitance; Radio frequency; Radiofrequency interference; Resistors; Voltage;

fLanguage

English

Publisher

ieee

Conference_Titel

Electromagnetic Compatibility, 1990. Symposium Record., 1990 IEEE International Symposium on

Conference_Location

Washington, DC

Print_ISBN

0-7803-7264-6

Type

conf

DOI

10.1109/ISEMC.1990.252748

Filename

252748