Hi I m designing a two stage ota using gm/id method. I have a problem in picking the length of the transistor. I have chosen a large length for large gain and good matching. And my ft is around 10 times the UGB of the ota. Are there any relationship between ft of the transistor and UGB of the amplifier. I mean is there any thumb rule that ft should be10 times the UGB ???
ft≥10×UGF is rather conventional relation, well working for 2st OTAs with all transistors biased in the same inversion region (usually with IC=1). It could be relaxed if load and 2nd stage mosfets are biased with higher IC than input pair.