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EPDT — July 31, 2025
Featuring: Chris Keimel, Menlo Micro CTO
Switches are the backbone to sensing, communications and power control systems. They route critical diagnostic signals in medical equipment, control high-speed data buses, form the basis of phased array antenna implementations, give us control over our electrified homes and vehicles, as well as helping control and protect the supply of power from the grid right through to the point-of-load.
This diversity of possible applications is matched by a diverse range of switching solutions - from traditional electro-mechanical relays (EMRs) to more sophisticated semiconductor-based switches, alongside the recent entry of micro-electro-mechanical system (MEMS) devices into both the RF and power control markets.
While all 3 of these prospective technologies can provide the basic functions of signal and power control, they do so via very different approaches. Each provides certain benefits, as well as system design trade-offs too.
The following article explores all 3 options. It highlights why MEMS switch solutions are combining the benefits of both EMRs and solid-state devices with fewer drawbacks, particularly in the growing markets of high-speed digital test and power control.
Comparing switch types
2 primary categories of conventional switches exist. These are EMRs and solid-state switches. They have very different form factors, thermal profiles, mechanisms of control and performance characteristics. EMRs were never intended to meet the speed challenge.
They were designed with simple criteria in mind - namely to exhibit low losses when on and be isolated when open. EMRs rely on metallic moving parts to change states, however these parts wear with every operation and become less reliable over ongoing cyclic activity. In an era where energy efficiency is paramount, EMRs have another drawback besides lack of speed.
In many cases they require a few hundred mW of power to drive the coil that keeps their contacts closed. Because they are ohmic, EMRs are typically used in high-fidelity RF signal applications plus power control - where speed, size and weight are less important, but where performance is paramount.
EMRs are not the only way to control signal and power. Semiconductors can also be employed. Solid-state switch technology required multiple platforms to cover both RF and power products, resulting in different material sets and fabrication procedures.
While initial semiconductor devices were designed for signal amplification, PIN diodes and gallium-arsenide (GaAs) MESFETs brought chip-scale control to RF signal applications in the 1970s/80s.
These technologies were later joined by RF CMOS nodes and RF silicon-on-insulator (SoI) devices that helped usher in the age of handheld mobile communications.
