f V in Microsoft Office Printer ECC200 in Microsoft Office f V .NET EAN13

f V using none toprint none on web,windows applicationc# ean 13 generator g V Microsoft Visual C# (1.10). Given a set of noise none for none sources, we can derive the minimum signal swing necessary for the system to be operational, 2. V sw -----------------------1 2 gj f V (1.11). This makes it clear t none none hat the signal swing (and the noise margin) has to be large enough to overpower the impact of the fixed sources (f VNf). On the other hand, the sensitivity to internal sources depends primarily upon the noise suppressing capabilities of the gate, this is the proportionality or gain factors gj. In the presence of large gain factors, increasing the signal swing does not do any good to suppress noise, as the noise increases proportionally.

In later chapters, we will discuss some differential logic families that suppress most of the internal noise, and hence can get away with very small noise margins and signal swings. Directivity The directivity property requires a gate to be unidirectional, that is, changes in an output level should not appear at any unchanging input of the same circuit. If not, an output-signal transition reflects to the gate inputs as a noise signal, affecting the signal integrity.

In real gate implementations, full directivity can never be achieved. Some feedback of changes in output levels to the inputs cannot be avoided. Capacitive coupling between inputs and outputs is a typical example of such a feedback.

It is important to minimize these changes so that they do not affect the logic levels of the input signals.. Page 30 Friday, January 18, 2002 8:58 AM INTRODUCTION 1 . Fan-In and Fan-Out Th none for none e fan-out denotes the number of load gates N that are connected to the output of the driving gate (Figure 1.16). Increasing the fan-out of a gate can affect its logic output levels.

From the world of analog amplifiers, we know that this effect is minimized by making the input resistance of the load gates as large as possible (minimizing the input currents) and by keeping the output resistance of the driving gate small (reducing the effects of load currents on the output voltage). When the fan-out is large, the added load can deteriorate the dynamic performance of the driving gate. For these reasons, many generic and library components define a maximum fan-out to guarantee that the static and dynamic performance of the element meet specification.

The fan-in of a gate is defined as the number of inputs to the gate (Figure 1.16b). Gates with large fan-in tend to be more complex, which often results in inferior static and dynamic properties.

. M N (b) Fan-in M (a) Fan-out N Figure 1.16 Definition of fan-out and fanin of a digital gate. The Ideal Digital Gat none none e Based on the above observations, we can define the ideal digital gate from a static perspective. The ideal inverter model is important because it gives us a metric by which we can judge the quality of actual implementations. Its VTC is shown in Figure 1.

17 and has the following properties: infinite gain in the transition region, and gate threshold located in the middle of the logic swing, with high and low noise margins equal to half the swing. The input and output impedances of the ideal gate are infinity and zero, respectively (i.e.

, the gate has unlimited fan-out). While this ideal VTC is unfortunately impossible in real designs, some implementations, such as the static CMOS inverter, come close..

Example 1.5 Voltage-T ransfer Characteristic Figure 1.18 shows an example of a voltage-transfer characteristic of an actual, but outdated gate structure (as produced by SPICE in the DC analysis mode).

The values of the dc-parameters are derived from inspection of the graph.. Page 31 Friday, January 18, 2002 8:58 AM Section 1.3 Quality Metrics of a Digital Design Vout g = - . Ideal voltage-transfer characteristic. VOH = 3.5 V; VIH = 2.35 V; VM = 1.64 V VOL = 0.45 V VIL = 0.66 V NMH = 1.15 V; NML = 0 none for none .21 V The observed transfer characteristic, obviously, is far from ideal: it is asymmetrical, has a very low value for NML, and the voltage swing of 3.

05 V is substantially below the maximum obtainable value of 5 V (which is the value of the supply voltage for this design)..
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