Construction Of Automatic Phase Changer

CHAPTER TWO
 COMPONENT DESCPRITION
COMPARATOR
The IC 741.e, the operational amplifier is used as a comparator in the circuit given below. As shown in the figure the IC 741 is a 8 pin IC in which the pin no.2 is known as the inverting terminal of the IC 741 because it is connected to the negative potential. The pin no.3 is known as the nom inverting terminal of the IC 741. The pin no.2 is connected to the reference voltage. The reference voltage is the voltage which we set as a standard voltage in the circuit. The pin no.2 is connected to the input voltage. Now if we applied the input voltage to the IC 741 then it will compare the input voltage to the reference voltage and if the input voltage is equal to the reference voltage then the output of the comparator is high.

                       ZENER DIODE
    A zener diode is a type of diode that permits current not only in the forward direction like a normal diode but also in the reverse direction if the voltage is larger than the voltage Breakdown voltage. The breakdown voltage of an insulator is the minimum voltage that causes a portion of an insulator to become electrically conductive. The breakdown voltages to make the diode is the minimum reverse voltages to make the diode conduct in reverse known as ‘zener knee’’ or zener voltage’’.
The device was named after Clarence zener. Clarence Melvin Zener was the American physicist who first described the electrical property exploited by the zener diode, which Bell Labs then named after him, who discovered this electrical property.
A conventional solid state diode
    Diode in electronics, is a two terminal electronic component that conducts electric current in only one direction. The term usually refers to a semi conductor diode, the most common type today . This is a crystalline block of semi conductor material connected to two electrical terminals will not allow significant current if it is reverse-biased below its reverse breakdown voltage. When the reverse bias breakdown voltage is exceeded, a conventional diode is subject to high current due to breakdown . Unless this current is limited by circuitry, the diode will be permanently damaged. In case of large forward bias [current in the direction of the arrow]. The diode exhibit a voltage drop due to its junction built in voltage and internal resistance. The amount of the voltage drop depends on the semi conductor material and the doping concentrations.
        A zener diode exhibits almost the same properties, except the devices is specially designed so as to have a greatly reduced breakdown voltage, the so called zener voltage. By contrast with the conventional device, a reverse biased zener diode will exhibit a controlled breakdown and allow the current to keep the voltage across the zener diode at the zener voltage. For example, a diode with a zener breakdown voltage of 3.2V will exhibit a voltage drop of 3.2 V, if reverse bias voltage applied across it is more than its zener voltage. The zener diode is therefore ideal for application such as the generation of a reference voltage [e.g for an amplifier].
Generally, an amplifier is any device that changes, usually increases the amplitude of a signal. The relationship of the input to the output of an amplifier is usually expressed as a function of the amplifier, and the magnitude stage, or as a voltage stabilizer for low-current application. The zener diode’s operation depends on the heavy doping.