Computer Aided Engineering and Programming ENGD1025 Operational Amplifier Filter

Computer Aided Engineering and Programming (ENGD1025)

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Title: Operational Amplifier Filters

Inverting High Pass OpAmp Filter

The High pass filter has a cut-off frequency of fH=12πR1C1

Figure 1. An Inverting opamphigh pass filter with “Vsin” as input signal, Vac = 1

Procedure

1. Design the circuit as seen in Figure 1 by following the same procedure as in previous lab session. 

2. Make the “AC” component of the Vsin input source equal to 1. This is required for doing the AC sweep.

3. Open a new simulation profile and run “AC Sweep” analysis with the following parameters:(Simulation settings –> AC sweep –> logarithmic -> from 10Hz to 10kHz, point/decade =1000)

4. Insert single voltage probe at the output terminal. Run the simulation and capture the frequency response and phase shift curves using the procedure mentioned in the “RC filter” experiment.

5. Calculate the cut-off frequency using the expression provided and verify this on the frequency response curve. Vout = 9V, Vin = 1V, therefore the gain is 9. The cutoff frequency is determined when the gain is 70.7% of this value.

6. Simulate the input and output sinusoidal waveforms using “Time Domain” analysis and comment on the phase shift between the waveforms. Separate plots for 100 Hz and 10KHz. Apply simulation settings accordingly.

Inverting Low Pass OpAmp Filter

In the Low Pass filter, the capacitor is placed in parallel to the feedback resistor as shown in Figure 2.The Low pass filter has a cut-off frequency of fL=12πR2C1

Repeat the above procedure for (steps 1 to 6) for this filter.

Figure 2. An Inverting opamplow pass filter with “Vsin” as input signal, Vac = 1

Extra:

• Repeat the above procedure for the non-inverting amplifier, i.e., high pass and low pass non-inverting opamp filters.

• Simulation settings for AC sweep: 1Hz to 10KHz, 1000 points/dec.

• Create an inverting band pass opamp filter with appropriate cut off frequencies.