Figure 851
the Modified Wilson Current Mirror of Fig $V_{t}=$ $0.4 \mathrm{~V}, \mu_{n} C_{o x}=400 \mu \mathrm{A} / \mathrm{V}^{2}$

Essay

Figure 8.5.1
The modified Wilson current mirror of Fig. 8.5.1 utilizes four matched transistors for which $V_{t}=$ $0.4 \mathrm{~V}, \mu_{n} C_{o x}=400 \mu \mathrm{A} / \mathrm{V}^{2}$ , and $V_{A}=3 \mathrm{~V}$ . It is required to design the circuit so that $I_{O}=0.2 \mathrm{~mA}$ with all transistors operating at $V_{O V}=0.2 \mathrm{~V}$ .
(a) Find the required value of $R$ .
(b) Find the required value of the $W / L$ ratio for each of the four transistors.
(c) Find the value of the output resistance $R_{O}$ .
(d) What is the minimum voltage permitted at the output?