FET or Transistor switches not draining

[PrescottDan]

When FET's or Transistors are used as switches, in the Off or Open State the FET and Transistor should be fully off and has drained off to near ground.

What additional components do you need to use to make a FET or Transistor when used as a switch to drain off and get to ground?

How do you know when a FET or Transistor when used as a switch is a Normally Closed or Normally Open Switch when looking at a schematic?

 

[chuckey]

You have to make sure that the gate has a DC return to earth. The NO or NC operation is totally dependent on the gate driving signal.
Frank

 

[betwixt]

I'm not sure what you mean by 'drained to near ground'. If you mean 'completely non-conducting', if there is no active driving voltage/current to force removal of bias, it is usually done with a resistor across the base/emitter or gate/source to leak away residual charge that might be enough to partially turn the device on.

It is very difficult to give an answer about any particular schematic as it depends on the configuration and if the switch has an obvious purpose. For example, a microprocessor driving a switch would give no clues as it would depend on the software it is running and from that, possibly the state of other pins or software states.

Brian.