Question 15.4: PROVIDING DC PATHS TO A PASSIVE FILTER A passive filter is s...
PROVIDING DC PATHS TO A PASSIVE FILTER
A passive filter is shown in Figure 15.14. The output is taken from node 9. Plot the magnitude and phase of the output voltage separately against the frequency. The frequency should be varied from 100 Hz to 10 kHz in steps of one decade and 101 points per decade.
The nodes between C_{1} and C_{3}, C_{3} and C_{5}, and C_{5} and C_{7} do not have DC paths to the ground. Therefore, the circuit cannot be analyzed without connecting resistors R_{3} , R_{4} , and R_{5} as shown in Figure 15.14 by dashed lines. If the values of these resistances are very high, say 200 MΩ, their influence on the AC analysis would be negligible.
The PSpice schematic of a passive filter with DC paths is shown in Figure 15.15.
The listing of the circuit file is as follows:
Example 15.4 Passive filter
| SOURCE VIN 1 0 AC 1V ; Input voltage is 1 V peak CIRCUIT R1 1 2 10K R2 9 0 10K ANALYSIS * AC analysis for 100 Hz to 10 kHz with a decade * increment and 101 points per decade: * Plot the results of AC analysis for the magnitude .END |
The frequency response for Example 15.4 is shown in Figure 15.16.
