31
Projects, Designs, and Technical Stuff / Re: role of optocoupler for biasing drain of amplifiers
« Last post by RFDx on Yesterday at 11:07:10 pm »When we want to mosfet to be ON we have to put at least 10V Vgs.
That is correct. I have attached a simplified circuit with a similar optocoupler type driver which should make things clearer. The load (think MMIC amp) is shown here as a simple 50 Ohm resistor. When turned on, the gate-source voltage Vgs in this case is 13.4V (37.4-24V). All voltage probes are referenced to real ground. When the load is turned off all voltages and currents are zero.