1. First Order Filter Circuit Section 14.1-14.3

2. First Order Filter Design LPF: RL HPF: RL LPF: RC HPF:RC

3. Filter Circuits High Pass Filter Low Pass Filter

4. Intuition

5. RL Low-Pass Filter

6. RL Circuit @ 100 Hz

7. RL Circuit @ 1000 Hz

8. RL Circuit @ 10,000 Hz

9. Summary Freq (Hz)Vout,mag/Vin,magPhase (deg) Approx imate (Phase) 1001.989/2=0.9945, (0dB)-5.7270 10001.459/2=0.7295, (-2.739 dB)-45.53-45 10,0000.269/2=0.1345, (-17.4 dB)-84.75-90

10. Rule of Thumb (1) Phase – The phase change starts one decade before the cut-off frequency – At the cut-off frequency, the phase change is 45 degrees. – At one decade after the cut-off frequency, the phase change is 90 degrees. – The phase change is complete one decade after the cut-off frequency.

11. Rule of Thumb (2) Magnitude – The magnitude change starts at the cut- off frequency. – The magnitude response is 0 dB at cut-off frequency. – 20 dB per decade after the cut-off frequency.

12. RL High Pass Filter

13. RL Circuit @ 1000 Hz

15. RL Circuit @ 10,000 Hz

16. Frequency: 1 KHz Low pass RL Filter Vout lags Vin High pass RL Filter Vout leads Vin