Power MOSFET Construction and Working Metal-oxide semiconductor field-effect transistors (MOSFETs) are a rather new addition to the unipolar transistor family. A distinguishing feature of this device is its gate construction. The gate is, for example, completely insulated from the channel. Voltage applied to the gate will cause it to develop an electrostatic charge. No current […]
There are two categories of SCR, the fast turn-off inverter grade SCR and relatively slow turn-off converter grade SCR. Some of the properties of these are interdependent and designers have aimed to combine them in most suitable manner. The application therefore decides what category is to be chosen. Once the category is chosen in each
A SCR (silicon-controlled rectifier) is a three-terminal semiconductor device that behaves like a diode but with an additional terminal. The additional terminal is called a gate, and when a small current flows into the gate, it allows a much larger current to flow from the anode to the cathode (provided that the voltage between the
Thyristor is a generic term for a broad range of semiconductor components used as an electronic switch. Like a mechanical switch it has only two states: on (conducting) and off (not conducting). Thyristors have no linear in-between state as transistors have. In addition to switching, they can also be used to adjust the amount of
Triac Working The triac is a three-terminal device essentially equivalent to two SCRs joined in reverse parallel (paralleled but with the polarity reversed) and with their gates connected together. The result is a bidirectional electronic switch that can be used to provide load current during both halves of the AC supply voltage. Triac connections, shown
Reverse Recovery Characteristics of Power Diode Ideally, a diode should have no reverse recovery time. However, the manufacturing cost of such a diode may increase. In many applications, the effects of reverse recovery time is not significant, and inexpensive diodes can be used. Depending on the recovery characteristics and manufacturing techniques, the power diodes can
TRIAC (Triode thyristor for alternating current) or triac is a bi-directional thyristor switch mainly used for AC control applications. It conducts in both directions, unlike the thyristors (SRCs) which conduct in one direction only. It can be considered to be equivalent to two thyristors connected in anti-parallel but having only three terminals. It has a
Static Characteristics of SCR Figure 1(a) shows the circuit symbol and the conventions for the different variables used in the V-I characteristics of the thyristor, shown in Fig. 1(b). The different modes describing the V-I characteristics are as follows: 1. Forward blocking mode: In Fig. 1(b), in forward blocking mode, when gate current IG =
Thyristors are a family of semiconductor switches having four or more layers, that is, p-n-p-n type of structure. Nowadays, thyrsitors with blocking voltage in excess of 6 kV and continuous current rating in excess of 4 kA are available. In a thyristor, if the ohmic connection is made to the first p-region and the last
The insulated gate bipolar transistor (IGBT) combines the advantageous features of MOSFET (such as voltage control, fast switching) and BJT (such as low ON-state losses and high OFF-state voltage capability. These devices have near ideal characteristics for high voltage (>100V) and medium frequency (<20 kHz) applications. The IGBT is a three terminal device with Like
Characteristics, Operation, & Construction of IGBT Read More »