This is called Wilson current source. The presence of MC4 is to boost output resistance of cascoded current source formed by MC5 and MC6 by gm4*(rc4//rc7).
The current goes through MC5 may not equal to Ibias, but is set by Vbias.
This is called Wilson current source. The presence of MC4 is to boost output resistance of cascoded current source formed by MC5 and MC6 by gm4*(rc4//rc7).
The current goes through MC5 may not equal to Ibias, but is set by Vbias.