2N7002 MOSFET : Pin Configuration & Its Working

The 2N7002 MOSFET is designed by ON Semiconductor using DMOS technology and high cell density. These transistors play a key role in reducing on−state resistance by providing reliable, rugged & very fast switching performance. The main disadvantage of this MOSFET is its low drain current.

2N7002 MOSFET is used where 400 mA of DC is required and delivers 2A of pulse current and specially used in low current and low voltage based applications like switching, controlling of mini servo motor and gate drivers of power MOSFET. This type of MOSFET is available in an SMD package thus used in compact applications. This article discusses an overview of 2N7002 MOSFET, working with applications.

What is 2N7002 MOSFET?

2N7002 is one kind of N-channel MOSFET that is used to decrease on-state resistance. This type of MOSFET includes three terminals like source (S), gate (G), and drain (D) where these three terminals are equivalent to emitter, base & collector terminals of BJT.

This transistor is used in high efficiency-based power management applications due to its high switching performance capability. As compared to BJT, 2N7002 MOSFET is a voltage-controlled device. Once the voltage is applied at the Gate terminal, then it controls the conductivity in between two remaining terminals like drain & source which is known as a channel. This channel length is mainly controlled through the voltage provided at the gate terminal in the MOSFET.

2N7002 MOSFET is available in the surface-mount package and it includes low input capacitance and low gate threshold voltage. This transistor is reliable and rugged because of its high saturation current capacity.

In normal operating conditions like VGs =0, this MOSFET doesn’t conduct but it will conduct simply once the voltage is provided at the gate terminal. So the conductivity of this transistor can be carried out throughout the majority charge carriers (electrons) instead of minority charge carriers (holes).

Pin Configuration

The pin configuration of 2N7002 MOSFET and its symbol is shown below. This type of MOSFET includes three terminals which are discussed below.

• Pin1 (Gate): This terminal controls the transistor biasing
• Pin2 (Source): Current flows out from this terminal
• Pin3 (Drain): This terminal allows the flow of current

2N7002 MOSFET Working

MOSFET nature can be simply defined through the movement of charge carriers like electrons. So, conduction between two terminals like source and drain can be carried out with the help of electrons. Once the voltage is provided at the gate terminal of MOSFET, then the charge carrier’s flow will be from the source to drain terminals.

2N7002 is an N-Channel MOSFET, so both the terminals like source and drain are composed with N-type material whereas the substrate is with P-type material.

When the positive voltage is applied to the MOS structure then it will adjust the charge allotment within the semiconductor. So, negative charge carriers are associated with the acceptor atoms to form the depletion region.

Once the positive voltage is applied at the gate terminal then it controls the flow of electrons. Similarly, when the positive voltage is increased at the gate terminal then it will attract several electrons which helps in expanding the path of the channel in between source & drain terminals. Thus, the MOSFET conductivity mainly depends on the intensity of applied voltage at the gate terminal.

Features & Specifications

The features and specifications of 2N7002 MOSFET include the following.

• It is reliable & rugged.
• The package is surface-mounted.
• Cell design density is high.
• It is available with maximum switching performance.
• Appropriate for logic level gate drive sources.
• On state resistance of this MOSFET is < 5Ω.
• Constant drain current or ID is 200mA.
• Voltage from drain to source or VDS is 60V.
• The gate threshold voltage of VGS-th (Min) is 1V.
• Gate threshold voltage or VGS-th (Max) is 3V.
• Turn ON & OFF time is 15ns & 8ns each.
• It is available in SOT23-3L & To-92 package.

Alternative 2N7002 MOSFETs are NTR4003, FDC666, FDC558. Equivalent P-Channel 2N7002 MOSFETs are FDN358P, BSS84 &Other N-Channel MOSFETs are IRF3205, BS170N, 2N7000, IRF540N, IRF1010E, etc.

How to use 2N7002 MOSFET?

The LED as a light sensor with a 2N7002 MOSFET circuit is shown below. We know that light-emitting diodes are used as an alternative to light sensors. In most semiconductor devices, LEDs generate voltage. So this property is used in a switch circuit to control the LED by turning OFF once illumination goes beyond a fixed level. In the following circuit, we can observe the LED working.

There are different types of LEDs available in the market which generate voltage but Green color LEDs are best in generating voltage. The voltage range produced by most of the LEDs ranges from 0.5 volts to 1.8 volts but the only drawback is their internal resistance which ranges from 100 to 1000 kΩ.

This schematic diagram is very easy to design and understand. Once the four LEDs in the circuit are activated like D1, D2, D3 & D4, they generate voltage. Once the level of this voltage exceeds above 2 volts, then this transistor will be ON & the voltage at the ‘drain’ electrode will be reduced to 0V. So, the Q2 transistor will be turned OFF then D5 LED will stop blinking.

An R1 = 50 Mega-Ohms resistor decreases the sensitivity of the above circuit, otherwise, the circuit will turn very sensitive toward the level of light. Additionally, once illumination drops, it will take some time to switch the LED as the input of the transistor signifies like 1000 pF capacitor & requires a few seconds to discharge it. To test this circuit, the whole circuit has to be arranged within a box from a compact flash card.

For SMD components, the copper tape is used as a carrier because the values of the resistors are limited to 20M, so the R1 resistor includes three values of resistors like 10, 20 & 20M

Where to use 2N7002 MOSFET/Applications

The applications of 2N7002 MOSFET include the following.

• Used in eMobility and power management based applications
• Used in switching and power MOSFET gate drivers.
• DC to DC converters.
• Used where on-state resistance low is necessary.
• Used to control motors
• Used in low voltage & current switching based applications
• It is a perfect alternative to reduce on-state resistance.

Thus, this is all about an overview of the 2N7002 MOSFET datasheet. This MOSFET replaces bipolar junction transistor in several applications due to no biasing current at the gate terminal but the capacitance can be charged through a small surge current at the gate terminal. This MOSFET is designed through DMOS technology and is ideal for applications that require 400 mA DC & deliver up to 4 A of pulsed current. Here is a question for you, at the gate terminal, why this MOSFET doesn’t use a current limiting resistor?