The gain of MOS tube will be worse when bias is applied to the source end.
Because there is an optimal operating point when the source end of the MOS tube is grounded, if the biased voltage is added, the optimal operating point will be offset, resulting in the working state of the entire MOS tube deteriorates and the gain decreases.
And bias will introduce a leakage current, reducing the input resistance of the MOS tube.
At the same time, it will increase power consumption, resulting in adverse energy efficiency for the entire system.
If it is necessary to use bias voltage to control the operation of the MOS tube, it can be optimized through circuit design, such as adding negative feedback and other methods.
In short, it is necessary to flexibly select according to the specific situation to avoid unnecessary influence.