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Unformatted text preview: of input voltages increases with increasing resistance. The unloaded condition is the equivalent of infinite resistance open circuit and has the largest range (97.9mV)
and the 98Ω has a range of 37.9mV. The output resistance is approximately 56.76Ω. To calcule this a voltage division relation was setup. The output voltage with a load of
986.5Ω (5.04V) is equal to to the output voltage of no load (5.33V) times the ratio of the load resistance to the load resistance in series with the output resistance. Solving for the
output resistance yields 56.76Ω. [Vout(loaded)=Vout(unloaded)*(Rload/(Rload + Routput))] Comments on Voltage Transfer Function - Open vs. Closed Loop:
The differences in the open and closed loop responses lies in the linear range of the two voltage transfer functions. The open loop response has a a slope in the linear range of
approximately ∞, while in the closed loop response the gain is 38.81 decibals. This results from the feedback network containing the a feedback resistor which is used to control
the amount of gain yielded by the Op Amp. Lower resistance in the feedback network results in lower gain. Open loop Op Amps are not reliable amplifiers because a small
voltage offset results in maximum gain. The closed loop Op Amps have controllable gain and allows the user to control the amplification of the incoming signal.
The other major diffence is the sign of the slopes. The open loop response has a positive slope because the voltage sweep is applied to the non-inverting terminal, and the opposite for closed loop. Inverting Amplifier Test Circuit (AC) Inverting Amplifoer 1 kHz Waveforms
Func.Generator: 50mV pk-pk, Sine Wave, zero offset, 1KHz
Scope: DC coupling and Time Div 500microseconds (place 1 kHz closed loop waveforms here) G a in ( d B) |Vout/Vin| =92.96 Phase Shift = 180 °
ECE2100 Lab #4 - Operational Amplifier Circuits Page 3 of 4
Inverting Amplifier Frequency Sweep(Note:Did not enable 50Ω load, Vout is apporx. half) Amplifoer : Bode Magni...
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This note was uploaded on 01/22/2014 for the course ECE 2100 taught by Professor Kelley/seyler during the Fall '05 term at Cornell University (Engineering School).
- Fall '05