ds u2248 u03b2 u2061 v gs v t u2062 where u2062 u2062 u03b2 u03bc u2062 u2062 c u2062 w l i out v ds g ds u03b2 v gs u2212 v t v ds which shows that i out may be a linear function of the input signal leading to an increase in linearity the amount of linearity achieved may be controlled by adjusting the ratio of the upper mosfet size to the lower mosfet size a load resistor 39 may be connected to the upper mosfet 34 another way of looking at it is to view the lower mosfet 36 as a normal mosfet which has its own transconductance gm the following derivation illustrates that the linearity of g m may be dependent on vds for a mosfet operated in the triode region i d u03bc u2062 u2062 c u2062 w l u2061 v gs v th u2062 v ds 1 2 u2062 v ds 2 the sensitivity of gm to variations in the input signal may be reduced by reducing the sensitivity of vds to variations in the input signal thereby increasing the linearity of the amplification however since u03b2 is function of process and temperature variation the gain of the amplifier may vary too one way to reduce that sensitivity is to bias the input stage so that u03b2vds is less sensitive to environmental variations fig3 shows an aspect of a bias circuit 50 for a linear input stage the bias circuit 50 may control the variation of the linear input stage transconductance to reduce sensitivity to process.