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Unformatted text preview: PROBLEM 1 A) Calculation for maximum current for NMOS in velocity saturation regime. Saturation occurs for Vds > Vgs-Vt, 6 , 2 225 10 0.68 n s a t n A k V V V 2 , ' , 2 6 2 2 A 0.3 0.71 226 10 1.8 0.37 0.71 257 V 0.2 2 D SAT d g s T D S A T d V W I k V V V L m I A m Maximum drive strength for a minimum size device is 227uA (sim)vs. 257uA (calc) Do not use PCLM for the channel length modulation. This parameter is unfortunately not the same as lambda and grossly overestimates of the actual channel length modulation. To calculate lambda, you might consider running the id vs vds sweep and calculating the small signal resistance, rds. This value is around 7k for the NMOS device. At a drain current of Id = 257uA and Vds of 1.8 volts, then be 1 1 0.55 7 257 ds d r I k A B) Calculation of the equivalent resistance. The equation in 3.42 will give an incorrect value because of the large channel length modulation. Estimate the on-resistance from the drain current at the beginning of the output voltage swing to the drain current when the output voltage reaches Vdd/2. In both cases, the drain current remains basically constant; 1 3...
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- Spring '09
- Trigraph, PMOS device, equivalent resistance, Channel length modulation, minimum size device