1. Define on-resistance on the conducting source-drain path

On-resistance describes the analog switch while its source-drain path is conducting. TI's TMUX1101 explanation defines it from the voltage and current associated with that path. The parameter is therefore about the selected conduction route, not a description of the switch's off-state isolation or its behavior when supply is absent.

TI also states that on-resistance varies with input voltage and supply voltage. Those conditions belong to the resistance description. An apparently simple comparison between resistance headlines can conceal different positions within the signal and supply context. Identifying the quantity first prevents a low-resistance label from becoming an unexplained statement about every operating condition of the switch.

This gives the review a useful starting point: determine which conducting path is being described and retain the applicable signal and supply conditions. Then examine how that resistance behaves as the intended signal changes. The normal on-state question is distinct from the existing powered-off-isolation question. A documented absent-supply protection feature does not characterize the selected path's resistance, just as an on-resistance entry does not describe the path's behavior without power.

2. Separate nominal resistance from variation across signal voltage

A resistance headline and resistance flatness answer different questions. The headline describes a resistance under its stated basis; flatness concerns how that resistance changes across the relevant signal excursion. ADI's switch tutorial explains that a MOS device's conducting resistance depends on signal voltage. A single typical value cannot represent every part of that relationship.

The tutorial describes combining complementary MOS devices to reduce on-resistance and reduce its variation with signal voltage. This supplies a mechanism for understanding why a switch can have a different resistance profile from an individual transistor. The useful point is the behavior of the conducting path as the signal moves, rather than a numerical ranking of the historical products used as illustrations.

Keep magnitude and variation on separate comparison axes. A requirement concerned with path loss needs the applicable resistance basis, while a requirement concerned with changes during a signal excursion needs the relevant variation description. One favorable headline does not complete both reviews. This distinction remains useful without reconstructing a curve, adopting an illustrative value or assuming that every complementary switch provides the same flatness under all supplies and signal conditions.

3. Relate resistance variation to attenuation and distortion

The on-state path forms part of the connected signal network. ADI discusses the switch resistance together with the source and load resistance as an attenuator. Thus the effect of a given conducting-path resistance depends on what surrounds it. The switch cannot be assigned a complete signal-loss meaning while the connected impedance relationship is omitted.

Resistance variation adds another question. If the conducting resistance changes with the applied signal, the attenuation changes with that signal as well. The tutorial distinguishes this modulation from a fixed gain error and connects it with distortion. A correction addressing a constant gain relationship does not, by itself, remove a relationship that changes over the signal excursion.

Consequently, compare attenuation and distortion separately even though both involve the conducting path. The first concerns the divider relationship at the condition under consideration; the second concerns how that relationship varies with signal level. A load description helps identify which mechanism matters. Neither a small nominal resistance nor a convenient calibration label supplies a distortion result for an unspecified circuit, and no numerical attenuation or distortion calculation is needed to preserve the distinction.

4. Keep high-impedance leakage error separate from low-resistance loss

Leakage supplies an additional error mechanism with a different impedance dependence. ADI's tutorial separates low-resistance circuits, where on-resistance effects are important, from high-resistance circuits, where leakage becomes significant. Reducing the conducting resistance therefore does not settle every precision-switching concern. The surrounding impedance changes which contribution deserves attention.

This explains why a resistance-focused comparison can be incomplete even after its signal variation is understood. A high-impedance receiving path can turn leakage into a voltage error through a different relationship from the low-impedance attenuator. The parameter being compared must match the mechanism of concern, rather than inheriting importance solely because on-resistance appears prominently in a switch description.

Bring the comparison together by retaining conducting resistance, its signal dependence and the connected impedance context. These identify why fixed attenuation, signal modulation and leakage need distinct evidence. The tutorial provides the qualitative relationships without approving a particular network or ranking switch technologies universally. The useful outcome is a defined on-state transfer question, separate from off-state leakage specifications, missing-supply protection and any claim that the selected switch behaves like an ideal connection.

Sources and further reading

TI TMUX1101/TMUX1102 SCDS410D on-resistance definition and ADI MT-088 Rev. 0, physical pages 2-5 qualitative mechanism prose. Historical product numbers, equations, curves and circuit examples are not used.