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V DD 2 in Microsoft Office Access barcode data matrix in Microsoft Office V DD 2

V DD 2 generate, create data matrix none in microsoft projects Office Word 1 = ------------------ V DD 2 V DD V 7 3 VDD ------------------ Microsoft DataMatrix ---------------- dV -- ------------ 1 -- V DD I DSAT ( 1 + V ) 9 4 I DSAT . 2 V DSAT (3.43). W with I DSAT = k" ---- ( VDD VT )V DSAT -------------L 2 A similar result can be obtained by just averaging the values of the resistance at the end points (and simplifying the result using a Taylor expansion): VDD 2 V DD 1 5 3 VDDR eq = -- ----------------------------------------- + ------------------------------------------------ -- ------------ 1 -- V DD I DSAT ( 1 + V DD ) I DSAT ( 1 + VDD 2 ) 4 I DSAT 2 6 A number of conclusions are worth drawing from the above expressions: The resistance is inversely proportional to the (W/L) ratio of the device. Doubling the transistor width halves the resistance. For VDD >> VT + VDSAT/2, the resistance becomes virtually independent of the supply voltage.

This is confirmed in halves, which plots the simulated equivalent resistance as a function of the supply voltage VDD. Only a minor improvement in resistance, attributable to the channel-length modulation, can be observed when raising the supply voltage. Once the supply voltage approaches VT, a dramatic increase in resistance can be observed.

. (3.44). chapter3.fm Page 108 Friday, January 18, 2002 9:00 AM THE DEVICES 3 . x 10. R eq (Ohm). 0 0.5. Figure 3.27 Simulated equiva lent resistance of a minimum size NMOS transistor in 0.25 m CMOS process as a function of VDD (VGS = VDD, VDS = VDD VDD/2).

. Design Data Equivalent Resistance Model Table 3.3 enumerates the equ ivalent resistances obtained by simulation of our generic 0.25 m CMOS process.

These values will come in handy when analyzing the performance of CMOS gates in later chapters.. Table 3.3 Equivalent resista Data Matrix 2d barcode for None nce Req (W/L= 1) of NMOS and PMOS transistors in 0.25 m CMOS process (with L = Lmin).

For larger devices, divide Req by W/L. VDD (V) NMOS (k ) PMOS (k ) 1 35 115 1.5 19 55 2 15 38 2.

5 13 31. Dynamic Behavior The dynamic response of a MO Microsoft Office barcode data matrix SFET transistor is a sole function of the time it takes to (dis)charge the parasitic capacitances that are intrinsic to the device, and the extra capacitance introduced by the interconnecting lines (and are the subject of 4). A profound understanding of the nature and the behavior of these intrinsic capacitances is essential for the designer of high-quality digital integrated circuits. They originate from three sources: the basic MOS structure, the channel charge, and the depletion regions of the reverse-biased pn-junctions of drain and source.

Aside from the MOS structure capacitances, all capacitors are nonlinear and vary with the applied voltage, which makes their analysis hard. We discuss each of the components in turn..

chapter3.fm Page 109 Friday, January 18, 2002 9:00 AM Section 3.3 The MOS(FET) Transistor MOS Structure Capacitances T barcode data matrix for None he gate of the MOS transistor is isolated from the conducting channel by the gate oxide that has a capacitance per unit area equal to Cox = ox / tox. We learned earlier that from a IV perspective it is useful to have Cox as large as possible, or to keep the oxide thickness very thin. The total value of this capacitance is called the gate capacitance Cg and can be decomposed into two elements, each with a different behavior.

Obviously, one part of Cg contributes to the channel charge, and is discussed in a subsequent section. Another part is solely due to the topological structure of the transistor. This component is the subject of the remainder of this section.

Consider the transistor structure of Figure 3.28. Ideally, the source and drain diffusion should end right at the edge of the gate oxide.

In reality, both source and drain tend to extend somewhat below the oxide by an amount xd, called the lateral diffusion. Hence, the effective channel of the transistor L becomes shorter than the drawn length Ld (or the length the transistor was originally designed for) by a factor of L = 2xd. It also gives rise to a parasitic capacitance between gate and source (drain) that is called the overlap capacitance.

This capacitance is strictly linear and has a fixed value.
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