# 21.6: Procedure


1. The circuit of Figure 21.5.1 is a second order band pass filter. Calculate and record the center frequency $$(f_0)$$ and mid-band voltage gain in Table 21.7.1

2. Assemble the circuit of Figure 21.5.1 using the medium speed op amp.

3. While monitoring the filter output with the dB meter, sweep the generator frequency about the expected $$f_0$$ until a peak is found. Record this frequency in Table 21.7.1. Measure the output amplitude, determine the gain and record this in Table 21.7.1 as well.

4. In Table 21.7.2, record the dB gain of the filter at 5 frequencies between 0.1 $$f_0$$ and $$f_0$$, and at 5 frequencies between $$f_0$$ and 10 $$f_0$$. Using these data, plot a graph of the filter response, and determine the bandwidth and Q of the filter.

5. Replace the capacitors with the 100n F units and repeat steps 3 and 4 using Tables 21.7.3 and 21.7.4.

6. The circuit resistors set the Q of the filter. To alter the Q of this circuit, replace the 2k2 with 1k2, the 22k with 39k, and the 47k with 75k.

7. Repeat steps 3 and 4 using Tables 21.7.5 and 21.7.6.

## 21.6.1: Computer Simulation

8. Build the circuit of Figure 21.5.1 in a simulator and run an AC Analysis. Be sure to run the plot from 10 Hz to approximately 100 kHz and use a decibel scale for the gain amplitude. Compare the plot to the graph generated from Table 21.7.2.

This page titled 21.6: Procedure is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by James M. Fiore via source content that was edited to the style and standards of the LibreTexts platform; a detailed edit history is available upon request.