Espelho de Corrente MOS Cascode

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Step 8 8.082P Refer to Figure 7.32 in the textbook for cascode MOS current mirror Write the expression for the Substitute 20 for I,, 160 for 4 for W1, and for 4 in order to find the overdrive voltage, 40 =0.25 V Step The overdrive voltages, Hence the overdrive voltage, = 0.25 V Find the ratio, by substituting 2 W. and W. in the ratio 2 4 {since W, 2 W L = W Substitute 20 for 40 for W2, 4 W1, and1 for L to calculate the W L 40 = 4 200 Therefore, the output current is, Step 8 It is known that the current Since, the output current, as indicated in the circuit diagram for a cascade MOS current mirror is same as the current, the output current is also obtained as 200 The expression for the gate source voltage is, Substitute 0.6 V for V, and 0.25 V for (since, =0.25 V in order to find the value of =0.25+0.6 Hence, the value of is obtained as 85 V. Step It is known that Since the currents I, and are equal and the widths and are equal, the gate source voltage, of the first component and the gate source voltage of the fourth component, are equal, Substitute the relation between the gate source voltages, in the expression, Since rearrange the Substitute 0.85 V for to find the value of =2(0.85) =1.7 V Therefore, the voltages and are, 1.7 respectively. Step The lowest possible voltage at the output is when satisfies the condition, The lowest possible output voltage is, Since the gate source voltages, GS2 and the currents, =1, assume equal magnitude in their relation, the gate source voltage of the third component becomes same as the gate source voltage of the first one, The lowest possible output voltage is, Substitute 1.7 V for 0.85 V for and 0.25 V for in order to obtain the value of =1.7-0.85+0.25 =1.1V Hence, the current-source operation is possible at the lowest voltage is. Step 8 Write the expression for trans conductance, of the components & and 8m The trans conductance of the first and the third components are equal, 8ml Substitute 200 for and 0.25 V for to get the value of 2(0.2) 0.25 mA/V Step of 8 Write the expression for the output resistance, for the first and the third components, and Substitute 10 V for and 200 for 10 200x10 Hence, the values of and of and are, and respectively. Step Write the expression for the output Substitute 1.6 mA/V for 20 for and 20 for Hence, the output resistance, R, of the mirror