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Transistors, Darlington Transistor, Mosfet Transistor



The history of the transistor—also known as the “transistor—began back in the days when tubes were used in computers. The focus of research at the time was precisely the improvement and reduction in the size of the valves, in addition to increasing their

efficiency, as they consumed a lot of energy.

Therefore, it was necessary for the valves to be replaced with a new, smaller and cheaper component. Military research began to become more and more complex and demanded that computers be reduced in size and could work at higher frequencies. The valves were not capable of this, leading electricians to look for other components.

In November 1947, scientists at the Bell Telephone laboratory discovered the transistor, although their research tried to go in another direction. They found that when a certain voltage was applied to one of the component's terminals, the signal that was output at the other terminal was amplified. Thus, the transistor became responsible for signal amplification, in addition to serving as a controller that interrupts or releases the passage of electrical current.

Its low cost allowed it to become an almost universal component for non-mechanical tasks. Transistors today have replaced almost all electromechanical devices in most control systems, and appear in large quantities in everything from electronics to cars.

Darlington Transistor Operation

Every transistor has three terminals, Collector, Base and Emitter. One of the terminals receives the electrical voltage (Base), and the others send the amplified signal (Collector to Emitter). The Base terminal is responsible for controlling this process, since the electrical current that enters and leaves the Collector and Emitter only when electrical voltage is applied to the Base terminal.

For simplicity, we can think of the transistor as a faucet.


The side of the pipe coming from the street is the inlet terminal (Collector) and the side from which it exits to the water is the outlet terminal (Emitter). When you turn the faucet on or off, your hand acts as the terminal (Base). However, we must remember that in Darlington transistors there are only two stages, it will either be on or off, comparing again with the tap, or it will be fully open or fully closed.

How to Test a Darlington Transistor?

NOTE: Use the multimeter on the Semiconductor scale.

1st test: the red tip must be on the BASE as a reference and when measuring it should not be removed, place the black tip on the COLLECTOR the measurement should be 0.3V to 0.8V. Then place the black tip on the SENDER and the measurement will be greater than 0.7V.

2nd test: put the black tip on COLLECTOR or on the carcass, and the red tip on the BASE and the measurement will be from 0.3 to 0.8v. Then put the red on theISSUER the measurement should also be from 0.3v to 0.8V. None of the terminals should be shorted.

Mosfet Transistor Operation

Physically it is the same as the Darlington transistor, but internally it has changes. The Mosfet transistor controls the current flowing between the “Source and Drain” terminals, through the voltage applied to the Gate terminal. Application codes for Mosfet Transistors usually have the initials IRF, 2SK and BUZ.

When voltage is applied to the Gate terminal, it allows electrical current to flow through the other Source and Drain terminals. The amount of voltage applied to the Gate (or control terminal) will determine how much current will be output through the terminal. If no voltage is applied to the control terminal, there is no electric current flowing.

Comparing again to a faucet, the more you open the register, the more water tends to come out, as with the Mosfet transistor, the greater the voltage applied to the Gate terminal, the greater the electric current that will flow from the Source to the Drain.

How to Test a Mosfet Transistor?

With the multimeter on the semiconductor scale, place the red tip into the SOURCE terminal and the other black tip into the SOURCE terminal. DRAIN the measurement will be 0.3V at 0.8v. None of the terminals should be shorted.

REMINDER: To identify the component's function, it must be verified through datasheet (data sheet), because physically we have several equal components, the only difference (visual) is the numbering.


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