A Unijunction Transistor (UJT) is a three-terminal semiconductor device. The main characteristics of UJT is when it is triggered, the emitter current increases re-generatively until it is limited by emitter power supply. Due to this characteristic feature, it is used in applications like switching pulse generator, saw-tooth wave generator etc.Construction of UJTThe UJT consists of an n-type silicon semiconductor bar with an electrical on each end. The terminals of these connections are called Base terminals (B1 and B2). Near to base B2, a pn-junction is formed between a p-type emitter and the n-type silicon bar. The terminal of this junction ... Read More

A transistor can be used as a solid state switch. If the transistor is operated in the saturation region then it acts as closed switch and when it is operated in the cut off region then it behaves as an open switch.The transistor operates as a Single Pole Single Throw (SPST) solid state switch. When a zero input signal applied to the base of the transistor, it acts as an open switch. If a positive signal applied at the input terminal then it acts like a closed switch.When the transistor operating as switch, in the cut off region the current ... Read More

Transistor as an AmplifierA transistor can increase the strength of a weak signal and hence it can be used as an amplifier in a circuit. The weak signal is applied between the emitter – base junction and output is taken across the load connected in the collector circuit.In order to achieve desired amplification, emitter – base junction must remain forward biased. For this, a DC voltage VBB is applied in the input circuit in addition to signal. This DC voltage is known as Bias Voltage and its magnitude is such that it always makes the emitter – base junction forward ... Read More

An SCR is a three-terminal, three-junction, and four-layer semiconductor device that is used to perform switching functions in power circuits.Sometimes the SCR is also called as Thyristor.Constructional Details of SCRThe SCR has three pn – junctions, and four layer of p and n type semiconductor joined alternatively to get pnpn device. The three terminals are taken – one from outer p – type layer called anode (A), second from the outer n – type layer called cathode (K) and the third from the internal p –type layer called gate (G).Working of SCRIn a SCR, the load is connected in series ... Read More

Important TermsAC Circuit − A closed path followed by alternating current is called as an AC Circuit.Resistance − The measure of opposition offered by a material in the path of electric current is known as resistance of that material. The element possessing the resistance is known as Resistor.Peak Value of Voltage or Current − It is the maximum value attained by an alternating quantity. It is also called as Amplitude.Average Value − The arithmetical average of all values of an alternating quantity over one cycle is called as average value. For sinusoidal voltage or current, $$\mathrm{I_{avg}=\frac{2I_{m}}{\pi}=0.637I_{m}}$$$$\mathrm{V_{avg}=\frac{2V_{m}}{\pi}=0.637I_{m}}$$Root Mean Square (RMS) value ... Read More

When a p–type semiconductor is suitably joined to n–type semiconductor, the contact surface of the semiconductors is called as pn–junction.Properties of pn – junctionThe p–type semiconductor has holes and the n–type semiconductor has free electrons as the majority charge carriers. When both p–type and n-type materials are suitably joined together to form pn–junction. At the junction, the free electrons from the n–side diffuse over to the p–side and the holes from the p–side to the n–side. Since both the materials are electrically neutral, so a positive charge is build up on the n–side of the junction and negative charge on ... Read More

A practical operational amplifier exhibits some limitations that should be considered in the design of instrument.The Physical Limitations of Operational Amplifier −Voltage Supply LimitationsFinite Bandwidth LimitationsInput Offset Voltage LimitationsInput Bias Current LimitationsOutput Offset Voltage LimitsSlew Rate LimitationShort Circuit Output LimitsLimited Common Mode Rejection RatioVoltage Supply LimitationsAn operational amplifier is power by an external DC power supply (+VCC and -VCC), which are symmetric and of the order of ± 10 V to ± 20 V. The effect of voltage supply limits is that amplifiers are able to amplify the signals only within the range of their power supply voltage. It is ... Read More

The operational amplifier (also known as Op-Amp) is a multi-terminal direct coupled high gain amplifier which consisting of one or more differential amplifiers and a level transistor and an output.The Op-Amp is a versatile device which can be used to amplify both DC and AC signals and these are mainly designed for performing mathematical operations like addition, subtraction, multiplication etc.Block Diagram of Operational AmplifierInput Stage − The input stage is the dual input, balanced output differential amplifier. This stage provides most of the voltage gain and introduces the input resistance of operational amplifier.Intermediate Stage − This stage is dual input, ... Read More

A Metal Oxide Semiconductor Field Effect Transistor (MOSFET) has four terminals − Source (S), Gate (G), Drain (D), Body (B). It is a semiconductor device which is used for switching and amplification applications in electronic circuits. In general, the body terminal is connected with the source thus forming a three terminal device just like an FET.The MOSFET is a voltage controlled device. Since its operation depends upon the flow of majority carriers only, hence MOSFET is a unipolar device.In other words, An FET that can be operated in the enhancement mode is known as MOSFET.Why the Name MOSFET? The gate ... Read More

An operational amplifier is a three-terminal device consisting of two high impedance input terminals, one is called the inverting input denoted by a negative sign and the other is the non-inverting input denoted with a positive sign. The third terminal is the output of the Op-Amp.Inverting Operational AmplifierIn the inverting operational amplifier circuit, the signal is applied at the inverting input and the non-inverting input is connected to the ground. In this type of amplifier, the output is 180⁰ out of phase to the input, i.e. when positive signal is applied to circuit, the output of the circuit will be ... Read More