vivkr
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We know that the gm/Id of a BJT is (1/Vt) where Vt = (kT/q) and at 300 K, (gm/Id) ~ 38. This gm/Id is independent of whether the BJT is PNP or NPN, made of Si, Ge or anything else.
We also know that the gm/Id of a MOS transistor is always less than the gm/Id for a BJT. At best, this can come within 0.8x - 0.9x of the BJT value, when the MOS transistor is in weak inversion. The above limitation cannot be surpassed for any given transistor.
My question: Is it possible in any way using circuit techniques to enhance the effective gm/Id of a transistor-based amplifier? If yes, then how? Naturally, if one were applying methods to boost effective gm, then Id is replaced by total current consumed by any blocks used in the process. I am wondering if positive feedback could be brought into play somehow.
Thanks & Regards Vivek
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