load capacitance, compensation, ota
Hi airboss
Actually I have heard it before. Take a look at this paper, and consider the sentences below:
H. Yang and D. Allstot, "Considerations for Fast Settling Operational Amplifiers", TCAS 1990.
" Our results show that the previous techniques based on Miller-multiplied capacitance models are suitable only for those amplifiers in which the first-stage pole is dominant prior to compensation. In most SC circuits, the internal opamps are transconductance amplifiers whch drive on-chp capacitive loads, and thus for these opamps, the second-stage pole is dominant."
"As previously stated, on-chip CMOS and GaAs transconductance amplifiers are usually second-stage dominant-pole systems with R,'C,'< R2'C2' in the model of Fig. 6(a). Conventional application of the Miller-multiplied capacitance effect in developing the equivalent circuit of Fig. 6(b) predicts that the first-stage pole moves to a lower frequency for a nonzero value of cgd and will become dominant if C and/or g,, is large enough as indicated in Fig. 8(a). This commonly-held view (c.f. [13, p. 3771 is incorrect in terms of basic root locus theory wherein the poles of a two-pole system can never cross one another as pole-splitting negative feedback is applied [l]."