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High Swing Bias
A high swing bias scheme for a cascode transistor is shown in Figure 1.
Assumptions

Figure.1 High swing bias generation circuit for cascode transistor
- Transistors M1-M5 are in saturation and Mx1-Mxn are in triode region
- Square law model of MOST is considered for analysis
Consider the general case where M3 and M4 have different aspect ratios. But M3 & Mx and M4 & M5 have same aspect ratios hence same . In such a case from square law model the channel current is given by,
(1)
From Eq.1,
(2)
If M4 and M5 are matched, and
.
From Eq.2
(3)
Substituting Eq.3 in Eq.1, we get
(4)
Solving for , we get,
where
- Mx1-Mxn devices replace quarter-size device
- Less sensitive to body effect[?][?]