ENG 100 Lab 4 Report

Operational Amplifier

ENG 100, Lab 3

May 6, 2004

Thursday 1-4pm


The purpose of this experiment was to become familiar with operational amplifiers, which can be used to isolate different sections of a large circuit for analysis. The first circuit used was a unity gain op amp buffer isolating a low pass RC filter and a high pass RC filter. The second circuit used was a band pass audio filter, which consisted of a second order RLC filter and a second order high pass RLC filter separated by a non-inverting op amp. Once each circuit was built using calculated resistor, capacitor and inductor values, the amplitude and time delay were measured at various frequencies.


The theoretical and experimental plots of Circuit A are extremely consistent, which implies a high degree of accuracy and success in this lab. Even though the pre-lab frequencies were different from those used in the lab, a common curve is found in both the amplitude and phase plots. Unfortunately, only the experimentally measured values of Circuit A can be compared with theoretical values calculated in the pre-lab, which inhibits an objective observation of Circuit B’s accuracy. It would be fair to say both plots support our basic hypothesis, based on the circuit’s definition. The large sources of inconsistency in this lab should be attributed to human error. Bad connections with alligator clips, exposed op amp wires touching and inaccurate circuit construction are the main factors in this labs error.

Part I:

Plot of phase (Degrees) versus frequency (Hz):

Part II

Plot of measured magnitude (dB) versus frequency (Hz):