The Analog-to-Digital conversion is a quantizing process whereby an analog signal is represented by equivalent binary states. Analog-to-Digital converters can be classified into two general groups based on the conversion technique. One technique involves comparing a given analog signal with the internally generated equivalent signal. This group includes successive-approximation, counter, and flash-type converters. The second technique involves changing an analog signal into time or frequency and comparing these new parameters to know values. This group includes integrator converters and voltage-to-frequency converters. The trade-off between the two techniques is based on accuracy vs. speed. The successive-approximation and flash are faster but generally less accurate than the integrator and the voltage-to-frequency type converters. Furthermore, the flash type is expensive and difficult to design for high accuracy.The successive-approximation A/D converters are used in applications such as data loggers and instrumentation, where conversion speed is important. On the other hand, integrating-type converters are used in application such as digital meters, panel meters, and monitoring systems, where the conversion accuracy is critical.
The zero-crossing detector detects whether the cycle is positive or negative, in which the current through an electrical heater may be turned "ON" for a few cycles then turned "OFF" for a few cycles, to maintain a given desired temperature. If the turn-on is only allowed to take place when the voltage is zero, no rapid increase in current takes place, as it does if switching occurs during the cycle.
The buffer is a logic circuit that amplifies the current or power. It has one input line and one output line. The logic level of the output is the same as that of the input; logic 1 input provides 1 output. The buffer is used primarily to increase the driving capability of a logic circuit. It is also known as a driver. There are basically two types of buffer: Tri-State Buffer and Bidirectional Buffer. The Tri-State Buffer is also known as a line driver or line receiver.
In digital system there is a need for power conversion, because the digital systems are supposed to operate at the voltage level of 5V or 12V DC. The power that we have supplied is not useful to the system. There are many power converters available.
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