We can now revert to the study of the transimpedance amplifier of Fig. 4.11, analyzing the stability issues with the feedback concepts just discussed. We first consider a more idealized case in which the output buffer is modeled as an ideal voltage-controlled voltage source. The open-loop amplifier has thus only two poles, one located at the input and one associated with the internal high impedance node. We then relax the hypothesis considering more realistic output stages.