sheldon
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Hi,
Still can't quite understand the circuit architecture, so it is difficult to answer in detail. One comment, is that open loop gain is relatively insensitive to bias current. For example, for a bipolar transistor: transconductance is gm = Ic/Vt and output resistance is ro= Va/Ic so the gain is Av = Va / Vt. To increase gain, alternative architectures are required. For example, using a cascode increases the output resistance, ro~Bo*Va/ Ic. So gain becomes Av = Bo * Va / Vt. MOS transistors have similar characterisitics, that is, increasing bias current does not usually increase gain. Since you are already using cascodes, the next step is to use regulated cascodes(gain boosting).
Sheldon
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