What I believe I am missing is that usually the stability is defined in terms of noise gain. When the blue curve hits -180 degrees at about 230 MHz the constructive interference condition is satisfied, however, the magnitude of the frequency response is below unity, therefore, there is no positive feedback that makes the circuit ring.Ģ. In the phase diagram of the Bode plot, the blue curve describes the difference between the voltage at the inverting input of the op-amp and the output of the op-amp. Is the presented front-end stable? If not, what part of the Bode plot tells me about the stability? What value do I need to adjust to stabilize the design?įrom my understanding, we need constructive interference at the inverting input of the op-amp as well as a gain larger than unity. In Multisim an AC sweep analysis gives the following Bode plot:ġ. I designed a front-end for the S5972 high-speed photodiode.
