# Bode plot finding K

I have no issue finding a and b. However to find K, I would like to know if I'm taking the right approach. I found $$a = 1/24$$ and $$b = 4$$ So how I'm planning on calculating K is as followed: $$2k/a = 8$$ since $$a = 1/24$$ then $$k = 1/6$$ Am I right? if not, please explain why this approach is wrong. Thank you. • This question appears to be unrelated to electronics design – Chetan Bhargava Apr 30 '14 at 4:45
• Where did you get the 8 for (2K/a) = 8 from? I'm pritty sure you shouldn't include the a. It's because your trasfer cunion should be normalized in the form of (s/a),(s/b). Then you take 20log(constant), which in your case 20log(2K) and determine where the graph starts from. – Adel Bibi Apr 30 '14 at 4:58
• @ChetanBhargava drawing bode plots is quite a basic EE thing actually. – Vladimir Cravero Apr 30 '14 at 5:02
• @VladimirCravero more towards mathematical side if you agree. – Chetan Bhargava Apr 30 '14 at 5:15
• "By signing this document, you are pledging to adhere to the honor system stating that all work performed here is strictly your own effort", the irony is too much for me. – hesson Apr 30 '14 at 5:21

You are given only the "unity frequency" or better "unity pulsation" (hope that's correct in English). You should take your transfer function and approximate it appropriately, then fill in the informations you have, i.e. at pulsation 8 gain is 1. The TF you are looking for is the TF stripped of all its poles and zeroes except the "origin pole" (again, hope that's correct), i.e.: $$G(s)=\frac{2K}{s}$$ that's because you are assuming $s\ll s_l$ where $s_l$ is the lowest singularity. Solving the previou equation for k: $$K=\frac{s\cdot G(s)}{2}=\frac{8\cdot 1}{2} = 4$$ that's about 12dB.