FET (JFET)

Field effect transistor or FET is a particularly interesting transistor and it can be of two types: the Junction Field Effect Transistor or JFET and the Metal-Oxide Semiconductor Field Effect Transistor (MOSFET).

What is an Op Amp? What is an Op Amp Open Loop?

Op Amp Open Loop Gain – Operational Amplifier Open Loop gain is given when there is no feedback path between the output and one of the two inputs

TRIAC. Power control on alternating current (AC)

Triac is a semiconductor device that belongs to the family of thyristor control devices. It is essentially two SCR connected in parallel and backwards, sharing the same gate.

What is a Zener diode?

The Zener diode is a special type of diode that allows the flow of current on the opposite direction of the arrow of the diode. This diode does not conduct until the applied voltage reaches or is greater of the breakdown voltage. Zener diode is very popular as Voltage reference element.

How to use op amps with a single rail power supply?

– Method 1: Voltage divider using two resistors.
– Method 2: Voltage divider using two Zener diodes.

The Semiconductor Diode

The semiconductor diode is the simplest semiconductor device and can be found in almost any electronic circuit. Diodes are manufactured with germanium and silicon (the most common).

FET characteristics

The N-channel JFET consists of a silicon bar of N-type semiconductor with two P type regions on both sides. JFET is a tri-terminal device whose terminals are called drain, source and gate.

What is a Schottky Diode? The Schottky diode or Schottky Barrier Diode unlike the semiconductor diode that has a P-N juntion, has an N-Metal junction. These diodes are characterized by their switching speed and low voltage drop when they are forward biased (typically 0.25 to 0.4 volts). Its symbol is showed on the following diagram. This diode works allmost like the […]

A phototransistor is essentially the same as a common transistor, but it can work in two different ways:

– As a common transistor, using the base current (IB)
– As a phototransistor, using the light that illuminates this element and that acts as the base current. (IP).

JFET Saturation and Breakdown regions The JFET Saturation region In this region the JFET has some linear features that are used in amplification. These features are similar to those of a BJT in the linear region. The JFET behaves as a voltage controlled (VGS) current source which ID is virtually independent of the voltage VDS. The equation that relates the current ID with the […]

JFET Cutoff and Linear regions JFET Cutoff region In this region the current flowing from the Drain to the Source terminals of the JFET is zero (ID = 0). In this case, the voltage between the gate and the source terminals is sufficiently negative to block the flow of the current through the channel between the drain and the source […]

Optocoupler: LED and  phototransistor The Optocoupler is a device that consists of a LED (light-emitting diode) and a phototransistor. When the LED emits light, it illuminates the phototransistor causing a current to flow trought it. These two elements are coupled in the most efficient possible way. The Ic output current of the optocoupler (phototransistor`s collector current) is proportional to the input current IF (LED`s current). The relation […]