difference between two transistors

[chalani]

Can anybody explain what is the difference between BSS138 N-Channel Logic Level Enhancement Mode Field Effect Transistor and the 2N7000 / 2N7002 / NDS7002A N-Channel Enhancement Mode Field Effect Transistor? and the various applications

[AJISH ALFRED]

Hi Chalani,

I haven’t used these transistors, but I’ve gone through their datasheet and found that they are almost similar regarding their features. Compare their electrical characteristics, their availability in the market and then decide which one to select ? Would you like to share the details of your application using this transistor with us?

[Ken]

 

Hi, Chalani.

 

Good question.

 

Generally, a logic device is on or off, whereas a standard mosfet acts 

as a variable resistor (between the drain and gate).

 

A general purpose mosfet gate may have a range (4-6) volts to saturate,

this may be a problem when driving with ttl or cmos logic (4.8 – 5v supply) 

 

It may not have sufficient gate voltage to saturate or completely turn on.

(if you are driving a relay or solenoid = possible device overheating) 

 

By using a logic version mosfet, you will get full saturation at logic level.

 

Of course, You must still consult the datasheet to see of  both TTL or CMOS levels are supported.

 

 

[Author]

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