The 2N7000 is housed in a TO92 package, with lead 1 connected as the source, lead 2 as the gate, and lead 3 as the drain. The BS170 has the source and drain leads interchanged.The 2N7002 variant is packaged in a TO-236 surface-mount package.
The 2N7000 and BS170 are two different N-channel, enhancement-modeMOSFETs used for low-power switching applications, with different lead arrangements and current ratings. They are sometimes listed together on the same datasheet with other variants 2N7002, VQ1000J, and VQ1000P.[1]
The 2N7000 is a widely available and popular part, often recommended as useful and common components to have around for hobbyist use.[2]
The BS250P is "a good p-channel analog of the 2N7000."[3]
Packaged in a TO-92 enclosure, both the 2N7000 and BS170 are 60 V devices. The 2N7000 can switch 200 mA. The BS170 can switch 500 mA, with a maximum on-resistance of 5 Ω at 10 V Vgs.
The 2N7002 is a part with similar (but not identical) electrical characteristics as the 2N7000 but different package. The 2N7002 is in a TO-236 package, also known as "small outline transistor" SOT-23 surface-mount, which is the most commonly used three-lead surface-mount package.[4]
Applications
The 2N7000 has been referred to as a "FETlington" and as an "absolutely ideal hacker part."[5] The word "FETlington" is a reference to the Darlington-transistor-like saturation characteristic.
A typical use of these transistors is as a switch for moderate voltages and currents, including as drivers for small lamps, motors, and relays.[1] In switching circuits, these FETs can be used much like bipolar junction transistors, but have some advantages:
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
MOSFETs, unlike PN junction devices (such as LEDs) can be paralleled because resistance increases with temperature, although the quality of this load balance is largely dependent on the internal chemistry of each individual MOSFET in the circuit
The main disadvantages of these FETs over bipolar transistors 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
