#20 shows what I meant. The transistor is acting as a "saturated" switch. With a logic-level FET, only 3 to 4 V are needed on the gate to switch amperes of load current.

The possible issue is that when the switch is off, the load GND is now floating. Depending on what the device is and its electrical environment, this can be a problem. If it is a completely stand-alone device or system, it shouldn't care.

Another possible issue is that the load system still has a connection to a power source that is not GND. Accidental contact between a circuit element (such as a resistor lead) and an external GND or some other potential can cause a current that might damage the system (or a human).

Note that both of these issues are rare. Personally, I've never had a problem with switching the GND. I mention them here so you can make an informed decision.

ak

 

#20 shows what I meant. The transistor is acting as a "saturated" switch. With a logic-level FET, only 3 to 4 V are needed on the gate to switch amperes of load current.

The possible issue is that when the switch is off, the load GND is now floating. Depending on what the device is and its electrical environment, this can be a problem. If it is a completely stand-alone device or system, it shouldn't care.

Another possible issue is that the load system still has a connection to a power source that is not GND. Accidental contact between a circuit element (such as a resistor lead) and an external GND or some other potential can cause a current that might damage the system (or a human).

Note that both of these issues are rare. Personally, I've never had a problem with switching the GND. I mention them here so you can make an informed decision.

ak

Would it be an issues for this devices, as shown on the Figure below. So there would be a single power, which I want to switch ON or OFF and there would be a RS-232 signal from PC or the other one on the left, where you have a DC power and Signals MOD IN from function generator?