A MOS current source of the type shown in Fig. 4.4 is to be designed to achieve minimum output current noise. The two transistors must be identical and the total gate area of the two transistors combined must not exceed 10 µm². Choose the W and Lof the devices under two different assumptions:

(a) 1/f noise dominates.

(b) Thermal noise dominates.

Assume that L_d and X_d are zero. The minimum allowed transistor length or width is 0.6 µm. Verify your design using SPICE.

Fig. 4.4:

VDD IIN IOUT = ID2 VOUT M2 M1 VIN