Question:
A very useful way to characterize the stability of the bias current ID is to evaluate the sensitivity of ID relative to a particular transistor parameter whose variability might be large. The sensitivity of ID relative to the MOSFET parameter K ≡ 1 2 kΩ (W/L) is defined as
![1964_Parameters.jpg](https://secure.tutorsglobe.com/CMSImages/1964_Parameters.jpg)
and its value, when multiplied by the variability (or tolerance) of K, provides the corresponding expected variability of id
![1658_Variability.png](https://secure.tutorsglobe.com/CMSImages/1658_Variability.png)
The purpose of this problem is to investigate the use of the sensitivity function in the design of the bias circuit of
Fig. 7.48(e).
Show that for Vt constant,
![1760_Bias circuit.jpg](https://secure.tutorsglobe.com/CMSImages/1760_Bias circuit.jpg)
For a MOSFET having K = 100 μA/V2 with a variability of ± 10% and Vt = 1 V, find the value of RS that would result in ID = 100 μA with a variability of ± 1%. Also, find VGS and the required value of VSS
(c) If the available supply VSS = 5 V, find the value of RS for ID = 100 μA. Evaluate the sensitivity function, and give the expected variability of ID in this case.