2N7000

The 2N7000 and BS170 are two different N-channel, enhancement-mode MOSFETs 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]

2N7000 / 2N7002
TypeMOSFET Transistor
Working principleN-channel
Pin configurationG = Gate, D = Drain, S = Source. The symbol doesn't always show the internal diode formed between the substrate and the source/drain/channel.
Electronic symbol
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 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 another different part with different resistance, current rating and 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:

  • 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
  • MOSFETs, unlike PN junction devices (such as LEDs) can be paralleled because resistance increases with temperature

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

References
  1. "2N7000/2N7002, VQ1000J/P, BS170" (PDF). Vishay Siliconix datasheet. Retrieved 28 March 2011.
  2. H. Ward Silver (2005). Two-way radios & scanners for dummies. p. 237. ISBN 0-7645-9582-2.
  3. Lucio Di Jasio; Tim Wilmshurst; Dogan Ibrahim (2007). PIC microcontrollers. Newnes. p. 520. ISBN 0-7506-8615-4.
  4. Ray P. Prasad (1997). Surface mount technology: principles and practice (2nd ed.). Springer. p. 112. ISBN 0-412-12921-3.
  5. Lancaster, Don (February 1986). "Hardware hacker". Modern Electronics. Richard Ross. 3 (2): 115. ISSN 0748-9889.
Datasheets


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