...circuitry

This is often called mixed analog-digital design.

...a

8#8 denotes the standard deviation of parameters. Accepting parts within 7#7 of the target parameter will maximise the yield of the processing[WE92].

...resistors

A unit resistor is a resistor of a specific geometry. The unit resistor has resistance 13#13, and any multiples of this value may be realised using a (natural) number of unit resistors.

...gives

0.1dB corresponds to 1.16%: 20#20

...variations

The term local implies that the region affected by the variation is `small'. Typically , the affected area is less than 9#9.

...used

See [O'L91]. The data have been compiled for a 31#1 CMOS process. Note that such data are process dependent, but the above guidelines may be used in the absence of more precise data.

...processing

Anisotropic processing, i.e. the processing speed differs with the crystal orientation, is the rule rather than the exception for small geometry processes.

...layout

The first moment of area is equal for the components which are matched.

...possible

Any process gradient may be approximated by the Taylor series in a small region around the origin. If the region is small, the approximation holds the best.

...ADC

The resistor was not laid out using common centroid techniques, but still demonstrated worst case matching better than 0.2%. We believe that the errors due to contact impedance in a common centroid layout structure would have been comparable.

...areas

The differences in field oxide thicknesses drawn in Figure 2.10 are deliberately exaggerated to underline the effect.

...by

55#55 denotes the sheet resistance of the resistor.

...impedance

In a typical 57#57 CMOS process, the well is 58#58's deep. If the side diffusion is approximately 70%, the area of curvature is roughly 59#59 long. The doping concentration in the area of curvature is lower than in the rest of the well area.

...N+

First, the effect of the curvature on resistance value is eliminated by avoiding the corners. Second, extending the well sufficiently means that N+ is not over the area of curvature even in case of misalignment.

...dependence

Transistors, resistors etc. Almost any parameter shows temperature dependence.

...saturated

The small-signal equivalent diagram is formed by observing the changes in the currents caused by small changes in the terminal voltages (V_GS, V_BS and V_DS).

...complicated

A thorough analysis of the problem may be found in [Tsi93].

...V_GS-V_T

Note that for values of V_GS-V_T below 50-100mV, the transistor operates in the subthreshold region, and the usual expressions for the channel current no longer hold.

...1V

The dotted curves show what happens to the current, when the expression no longer holds.

...required

E.g. modem front ends.

...process

For a P-Well process, the V_DD must be common external to the circuit. For twin-well processes, the doping of the substrate must be carefully considered.

...supplies

A double bond is often desired for supplies. If a pad has already got a double bond, then a third bond is usually not permitted.

...is

Equation 6.2 can be used with relatively little error for almost all printed circuit board connections.

...nodes

E.g. the output nodes of an operational transconductance amplifier (OTA), or the compensation node of an internally compensated operational amplifier.

...capacitor

In a double poly-layer process.

...lines

The recommendation is for an N-well process.

...switches

This is often called clock feedthru.