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Is is possible to use a NPN transistor as a normal switch?

If I put 5 V on the transistor base the switch is closed and if there is 0 V on the base the switch is open.

Does the transistor need to be connected to Vdd or GND? I want this switch to be in the middle of a circuit.

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    \$\begingroup\$ The answer depends a lot of parameters. Will it be a series switch? What are the DC voltage levels of source and target? The amount of current flowing? Frequency? \$\endgroup\$ Oct 21, 2018 at 20:50
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    \$\begingroup\$ Is is possible to use a NPN transistor as a normal switch? Probably yes but answering your question properly goes too far for an answer here as there are simply too many unknowns. What you should do is look at examples where a transistor is used to switch something on/off. If what you need cannot be found then very likely you cannot use a transistor as a direct replacement for a switch. If a transistor can be used as a switch depends entirely on the circumstances and that then dictates how the transistor can be used. Also show your circuit ! \$\endgroup\$ Oct 21, 2018 at 20:50

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No, an NPN transistor is not the same as a "normal switch".

A mechanical switch will conduct current equally well in either direciton but a transistor will not.

A mechanical switch has almost no voltage across it when it is closed, but a transistor will have 0.2V to 0.5V across it when it is saturated.

The transistor requires that the base terminal be about 0.7V higher than the emitter terminal, which limits the voltage range over which the transistor can conduct current. A mechanical switch has no such limits.

By the way, applying 5V directly to the base of an NPN transistor may damage it. You need a resistor in series with the base to limit the base current.

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