# DC-Gain from bode plot

I have the following bode plot and I am trying to determine the DC-Gain and the Gain at high frequencies How do I calculate the DC-Gain from this plot? Matlab's function dcgain() says that it is equal to 2. How do determine this?

• If the gain, in terms of output signal magnitude divided by input signal magnitude, is $G$ then the gain in dB is $20log_{10} G$ – Chu Apr 6 '17 at 19:04
• From the graph 6dB----> 6/20 = 0.3;---->10^0.3 = 2[V/V] – G36 Apr 6 '17 at 19:06

## 1 Answer

Gain(dB) = 20 x log(amplitude Gain)

amplitude Gain = 10 ^ (Gain(dB)/20)

In your case it is 6dB -> amplitude Gain of ~2

• This assumes the Bode plot captures all the important behavior and there isn't some low frequency pole or zero at a frequency lower than the left edge of the graph. – The Photon Apr 6 '17 at 19:19
• If there was a pole at lower frequency, the phase could not be zero. The only scenario where the DC gain would be different would be because of a combination of a pole AND a zero at lower frequency, not because of a single pole. – Claudio Avi Chami Apr 7 '17 at 5:06