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Does a switch cause a voltage drop?
Resistance anywhere in a current path causes a voltage drop. If the resistance of the switch contact surfaces becomes great enough, a voltage drop across the contacts that was not engineered appears. This voltage drop robs voltage, intended for the load, because it is in series with the load.
What happens to voltage during a voltage drop?
Voltage drop is the loss of voltage caused by the flow of current through a resistance. Voltage drop (VD) occurs when the voltage at the end of a run of cable is lower than at the beginning. This condition causes the load to work harder with less voltage pushing the current.
What is the voltage drop specification for ground?
The voltage drop between the power and ground side of a particular circuit will generally be 0.1 volts or less. Expect a voltage drop of 0.2 volts or less from one end of a particular copper wire or cable to the other. A switch will usually create a voltage drop of 0.3 volts or less.
When does a MOSFET have a positive voltage?
The resistance is less when the MOSFET is more enhanced, so a more positive voltage on an n-channel MOSFET gate relative to the source. The equivalent resistor might be tens of ohms for a small MOSFET down to milliohms for a large power MOSFET.
How does gate threshold voltage affect MOSFET conduction?
The Gate threshold voltage determines the voltage difference you need to apply to the gate to make the mosfet conduct. The Gate to Source max voltage (max Vgs) is a critical factor that must not be exceeded (even for a few nS) or the MOSFET can be destroyed.
How does a low value resistor work on a MOSFET?
Using a low value resistor between the MOSFET driver and the MOSFET gate terminal dampens down any ringing oscillations caused by the lead inductance and gate capacitance which can otherwise exceed the maximum voltage allowed on the gate terminal. It also slows down the rate at which the MOSFET turns on and off.
How is a double enhanced MOSFET used in a switch?
A double enhanced mosfet incorporates two diodes cathode to cathode. A MOSFET only requires gate current during the switching edge, to charge the GS capacitance. This gate current can be high. Use a N-Channel MOSFET with Source connected to 0V (either directly or via a current limiting resistor) and the load connected to Drain.