What is the main difference between JFET and MOSFET transistors? Here I will talk about the difference from a practical point of view, and the theory can be found in various sources
MOSFET transistors are used mainly in high-power equipment as an electronic key and it is quite easy to find such transistors in equipment. But it will be difficult to find JFET transistors, since they are used in low-power equipment and can be found in electret microphones.I took apart one of the microphones and here it is, a 2sk1227 transistor, 2sk596 is also often used, these are JFET transistors
So, what is the difference between these transistors? MOSFET transistors are initially open and JFETs are initially closed and this can be checked with a simple ohmmeter.
As a MOSFET I used the IRFZ46N transistor. At the drain-source terminals the ohmmeter will show infinite resistance.The JFET transistor will show some resistance on the drain-source terminals, in my case it is 1.3 kOhm.
In practice, it will look like this. I connected a load-LED to the drain of the transistors through a current-limiting resistor of 320 Ohm and supplied power of about 7 Volts. With a MOSFET transistor, the LED will not initially light, since the transistor is open.
To close the transistor, you need to touch the positive terminal of the power source and the gate of the transistor with two fingers. The LED lights up.
To open the transistor, touch the negative terminal of the power supply and the gate with your fingers. The LED will now not light.
Now I will do the same with the JFET transistor. When power is supplied, the LED will light and if you touch the gate and the power supply terminals with your fingers, the LED will still light and there will be no reaction. The transistor will be permanently closed.
How to open a JFET transistor? You need to supply negative power to the gate relative to ground (we are talking about n -ch).
Now the transistor is open and the LED is out.
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