Absorptive options of the ADG901, ADG918, ADG936, and ADG904 switches are available. What are these and where would they be used?
The ADG901 (SPST), ADG918 (SPDT), ADG936 (dual SPDT), and the ADG904 (SP4T) parts are described as absorptive (matched) switches, because they have on-chip 50-ohm-terminated shunt legs. The figure below shows the internal configuration of the ADG918 absorptive switch.
An absorptive switch has a good impedance-match and thus a good return loss (or voltage standing-wave ratio (VSWR)), on each port, regardless of the switch mode. It should be used when there is a need for proper back-termination in the off channel, to maintain a good return loss. An absorptive switch is therefore ideal for applications that require minimum reflections back to the RF source. It also ensures that the maximum power is transferred to the load in a 50-ohm system. It is also worth noting that a series-shunt switch configuration also helps to improve the off-isolation.