2N7000

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The 2N7000 is a N-channel, enhancement-mode MOSFET used for small-signal switching applications.

Packaged in a TO92 enclosure, the 2N7000 is a 60 volt, device capable of switching in the 200-350 milliamp range with an on-resistance of 0.3-5 ohms.

The main use of the 2N7000 is as a switch for low voltages and currents. In switching circuits, the 2N7000 can be used much like an NPN Transistor, but has advantages:

low threshold voltage means no gate bias required
high input impedance of the insulated gate means almost no gate current is required
consequently no current-limiting resistor is required in the gate input

The main disadvantages of the 2N7000 over a bipolar transistor in switching are the following:

susceptibility to cumulative damage from static discharge prior to installation
circuits with external gate exposure require a protection gate resistor or other static discharge protection
Non-zero ohmic response when driven to saturation, as compared to a constant junction voltage drop in a bipolar junction transistor

The circuit symbol for the 2N7000 generally does not show the internal Diode formed by the substrate connection source to drain.