Left Navigation

Relay Basics

General Knowledge of Relays

Back to Relay Basics index
rybasic2-6 mos-fet

MOS FET Relays


MOS FET relays are semiconductor relays that use MOS FET for their outputs.

Non-contact relays, mainly used for switching and connecting signals, are used in a wide range of applications, including semiconductor test equipment, measuring instruments, and security equipment.

About MOS FET Relays


Ultra-small and lightweight SSOP, USOP and other new ultra-small packaging VSON are emerging, which contributes to miniaturization of the entire device.
Low drive current The drive current is about 2 to 15mA under the recommended operating condition (normal). We also have a minimum of 0.2 mA products which contribute to energy saving of whole device.
Longer-life Our MOS FET relays have a non-contact structure using an optical signal transmission method. We have achieved long durability without deterioration of life due to contact friction.
small leakage current Because of its high resistance to external surges and no added snubber circuit, the leakage current is extremely small, typically 1 nA or less in the off state. (G3VM-□GR□,-□LR□,-□PR□,-□UR□)
superior impact resistance Since the internal parts are completely molded and there are no mechanical parts such as movable parts, they are excellent in shock resistance and vibration resistance.
Quiet sound Since there is no switching noise caused by metal contacts unlike machine relays, it contributes to noise reduction of device.
High insulation Since there is no switching noise caused by metal contacts unlike machine relays, they contribute to noise reduction of device.
Precise control of small analog signals Since the dead band is extremely small compared to a triac etc, the input waveform of a small analog signal is converted into an output waveform with little distortion.


Product map by MOS FET relay type
Product map by MOS FET relay type


Basic structures and operating of MOS FET relays
Internal structure

MOS FET relays consist of following three chips:

  1. LED chips
  2. PDA (photodiode array) chip
  3. MOS FET chips
Operational principle

MOS FET relays operate according to the following principles.

  1. The LED lights when the current flows to the input side.
  2. The light from the LED is received by the photodiode array, which generates electricity to convert the light back to a voltage
  3. This voltage passes through the control circuit to become the gate voltage to drive the MOS FET.

Application example

FA/Industrial equipment

Machine tools, custom power supplies, FA devices (programmable controller/temperature controller/timer)

ApplicationStatus output, various signals, small solenoid valve,　power supply external output of small motor
  • Machine tools
    Machine tools
  • Control panel
Test measurement/testers

Semiconductor test equipment (ATE)/semiconductor test interface boards, oscilloscopes, data loggers, I/O boards

ApplicationMeasurement signal switching, power supply
  • ATE
    (Semiconductor test equipment)
  • Tester
Security devices

Smoke and gas detectors, home security panels, human body detection sensors and TV doorphones

Applicationstatus output, various signal output, small solenoid valve, power supply external output of small light
  • Smoke and gas detector
    Smoke and gas detector
  • Home security panel
    Home security panel
Amusement equipment

paper money discrimination units, game ball and medal lending machines (interposed machine), IT equipment

Applicationstatus output, various signals
  • Gaming machines
    Gaming machines