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Switch Microloads

FAQ No. FAQ02152

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Are Solid-state Relays unable to switch microloads?


The minimum load currents in the following table can be switched using Solid-state Relays with Power MOS FET outputs (G3DZ/G3RZ).

Minimum Load Currents for G3DZ and G3RZ

Load voltageG3DZG3RZ
200 VAC100 μA100 μA
100 VAC10 μA100 μA

The following applies to AC Solid-state Relays with triac or thyristor outputs and to DC Solid-state Relays with power transistor outputs.

Solid-state Relays with AC Output:

At present, the minimum load current for most Solid-state Relays is 100 mA (50 mA at an ambient temperature of 25°C or higher) considering the degree of current (holding current) required because of problems with the load failing to reset due to leakage current and the output elements remaining ON.

Microloads below these values can be supported by connecting bleeder resistance in parallel with the load. By using MOS FETs, however, microloads can be directly switched without bleeder resistance.

Bleeder Resistance

100 VAC5 to 10 kΩ3 W
200 VAC5 to 10 kΩ15 W

Solid-state Relays with DC Output:

Leakage current may cause the load to fail to reset.

There is generally no problem for most microload switching with Solid-state Relay models with a leakage current of 0.1 mA or less. Caution is required, however, for G3CN-D Solid-state Relays, G3FD Solid-state Relays, G3HD Solid-state Relays and other models with large leakage current.

The following table provides a rough guide to bleeder resistance if reset failure occurs using the G3CN-D, G3FD, or G3HD.

Bleeder Resistance

5 VDC1.6 kΩ1/4 W
12 VDC620 Ω1 W
24 VDC330 Ω5 W