Berti wrote on Aug 3rd, 2009, 12:00am:T4 might circumvent the problem by providing a levelshift. However, the bias current through T4 must be small compared to the main branch.
Cheers
Sorry for dominating these conversations, but I hope I'm being helpful.
The circuit on the right has been used for a long time. It is a wide swing regulated current source. As you guessed, M4 provides level shifting so that M1 has the minimal voltage across it without going linear. The current does not have to be small, but M1 must be sized to handle it. In fact, if the current is too small it will reduce the phase margin of the gain boosting circuit.
rg