ADLINK PCI-7258 - Manual (Page 28)

20 • Operation Theory
4
Operation Theory
4.1 PhotoMos Relay Output
The PhotoMos relay has LED inputs and MOSFET outputs that provide input-
output isolation. When a signal current flows into the LED input pin, the
emitted light from the LED is detected by the photoelectric element (solar
cell), which is mounted opposite to the LED. The photoelectric element then
converts the received light to a voltage, which charges the MOSFET gate on
the output side. When the voltage reaches a preset voltage value, the
MOSFET begins to conduct and turns on the load. The simplified circuit of
PhotoMos relay is shown in figure 4 below.
Figure 5: PhotoMos relay schematic