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0. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. Linear scale. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. Logarithmic scale. A logarithmic scale compresses large values and allows a large range to be covered without losing resolution for the smaller values. 40. 30. Cutoff Frequencies -3dB.
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0 1 2 3 4 5 6 7 8 9 10 Linear scale 1 2 3 4 5 6 7 8 9 10 Logarithmic scale A logarithmic scale compresses large values and allows a large range to be covered without losing resolution for the smaller values.
40 30 Cutoff Frequencies -3dB 20 Av db Linear scale AvMid 10 0 -10 20 db per decade rolloff -20 -30 -40 10 100 1k 10k 100k 1Meg 10Meg Frequency in Hz (log scale)
Ideal Bode plot of a dc amplifier with two break frequencies. 50 dB 40 dB 20 dB/decade 30 dB 20 dB 40 dB/decade 10 dB 0 dB 10 Hz 100 Hz 1 kHz 10 kHz 100 kHz fb1 fb2
R 1 1 f2 = AV = 2pRC ( ) 2 f 1+ f2 C Amplitude response of RC lag circuit f2 10f2 100f2 1000f2 0 dB -20 dB -40 dB -60 dB
f f2 R Angular response of RC lag circuit C f = -arctan 0.1f2 f2 10f2 0o -45o -90o Phase angle is between 0 and 90 degrees
Cutoff Frequencies -3dB (f2) 90 Angle(Av) degrees 45 0 -45 Change at -45degrees/decade -90 10 100 1k 10k 100k 1Meg 10Meg Frequency in Hz (log scale)