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I understand how to get curve 1,2,3 and 4. the last step is "The overall curve is shifted vertically by an amount determined by the multiplicative constant of the transfer function''. as you can see the multiplicative constant is 20dB but what I don't get is how does this result in curve 5? in other words how they got curve 5 from shifting everything by 20dB so that the gain is 60dB? can anyone explain this for me please?

enter image description here

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  • \$\begingroup\$ the bode bode is correct, but I don't understand how they got curve 5 \$\endgroup\$
    – user65652
    Commented Nov 7, 2015 at 16:46

1 Answer 1

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Curve 1 rises from a zero and ramps up to intersect the 100 rad/sec point at 40 dB. At this point curve 2 cancels the rise to a flat line remaining at 40 dB. Curve 3 comes along at 100,000 rad/sec and starts declining the "flat" to a 20dB/decade slope downwards.

Curve 4 raises the whole thing by 20 dB to coincide with curve 5 on the diagram.

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  • \$\begingroup\$ how do you know at 100 rad/sec you get 60 dB? \$\endgroup\$
    – user65652
    Commented Nov 7, 2015 at 16:59
  • \$\begingroup\$ Curve 1 gets flattened by curve 2 at 100 rad/sec therefore it remains at 40 dB but curve 5 lifts it up by 20 dB. \$\endgroup\$
    – Andy aka
    Commented Nov 7, 2015 at 17:03
  • \$\begingroup\$ where is the math? I understand the concept visually. how do you come up with these numbers? \$\endgroup\$
    – user65652
    Commented Nov 7, 2015 at 17:04
  • \$\begingroup\$ If you didn't have curve 5 what would you see ? \$\endgroup\$
    – Andy aka
    Commented Nov 7, 2015 at 17:04
  • \$\begingroup\$ 20 dB/decade is etched onto my soul. I've known it for so long that I don't need to prove it any more. Curve 1 rises at 20 dB/dec and curve 2 falls at 20 dB/dec - when both are applied together (100 rad/sec and above) a flat line results. \$\endgroup\$
    – Andy aka
    Commented Nov 7, 2015 at 17:06

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