The 2N7000 and BS170 are two different

N-channel The field-effect transistor (FET) is a type of transistor that uses an electric field to control the flow of current in a semiconductor. FETs (JFETs or MOSFETs) are devices with three terminals: ''source'', ''gate'', and ''drain''. FETs control ...

enhancement-mode In field-effect transistors (FETs), depletion mode and enhancement mode are two major transistor types, corresponding to whether the transistor is in an on state or an off state at zero gate–source voltage. Enhancement-mode MOSFETs (metal–o ...

MOSFET The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET) is a type of field-effect transistor (FET), most commonly fabricated by the controlled oxidation of silicon. It has an insulated gate, the voltage of which d ...

s 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. The 2N7000 is a widely available and popular part, often recommended as useful and common components to have around for hobbyist use. The BS250P is "a good p-channel analog of the 2N7000." 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 similar part with the same 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 Surface-mount technology (SMT), originally called planar mounting, is a method in which the electrical components are mounted directly onto the surface of a printed circuit board (PCB). An electrical component mounted in this manner is referred ...

, which is the most commonly used three-lead surface-mount package.

Applications

The 2N7000 has been referred to as a "FETlington" and as an "absolutely ideal hacker part." 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. 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

References

External links

Application Notes for Experimenters

demonstrates extremely high gate impedance with a simple LED circuit
Driving a single MOSFET
Detailed description of usage of a similar MOSFET ;Datasheets
2N7002, 300mA, SOT-23 case
NXP Semiconductors
NX7002AK, 300mA, SOT-23 case
NXP Semiconductors
2N7000, 200mA, TO-92 case
, On Semiconductor
BS170, 500mA, TO-92 case
, On Semiconductor {{DEFAULTSORT:2n7000 JEDEC standards Commercial transistors MOSFETs