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 […]
LDR – Light Dependent Resistor – Photoresistor LDR (light dependent resistor) is a resistor that has a value that varies depending on the amount of light it has on it. Photoresistor is manufactured with crystalline structure materials using its photoconductive properties. The most common crystal used are: cadmium sulphide and cadmium selenide. The photoresistor (LDR) symbol is: LDR’s range values goes from […]
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 […]
Seven Segments Display, 7-segment Display The 7-segment display, is a component that is used to represent numbers in many electronic devices. Today, it is very common to find LCDs in many electronic equipments (due to its very low energy demand), but there are many that still use the 7-segment display for its simplicity. This element is made in a way […]
LED – Light-emitting diode Light-emitting diode (LED) is a special type of diode, that emits light when it is forward biased. There are LEDs of various colors. LED colors depend on the material with which they were built. There are red, green, yellow, amber, infrared, etc. If a current flows through a semiconductor diode, there are electrons and holes […]
The SCR (Silicon Controled Rectifier) The SCR is a 4 layers semiconductor device which behaves almost as an ideal switch. Thyristor symbol and structure are shown at right. A = anode, G = gate and K = cathode. Basic Operation of a SCR To understand the SCR operation, the following picture shows an equivalent circuit. An IG current is applied to […]
Darlington transistor The Darlington transistor is a special type of transistor which has a high current gain. It consists of two internally bipolar transistors being connected in cascade. The T1 transistor delivers on its emitter terminal, a current that goes to the base of the T2 transistor. The current gain equation of a typical transistor is: IE = ßxIB (collector current is […]