ENS6156 : Analog Electronics Assignment
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Added on 2019-10-31
ENS6156 : Analog Electronics Assignment
Added on 2019-10-31
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Running head: ANALOG ELECTRONICS 0ANALOG ELECTRONICSName of StudentInstitution Affiliation
ANALOG ELECTRONICS 2DESIGNING OF INTERFACE CIRCUIT FOR CAPACITIVE SENSOR APPLICATIONAbstract This case study basically emphasizes the design of interface circuit for capacitive sensingapplication, this circuit is employed for doing the interfacing with the micro sensors where transducers (capacitive) are highly used[ CITATION Mic12 \l 1033 ]. These circuits are designed andfabricated using typical CMOS (Complementary Metal-Oxide-Semiconductor) processes and it is integrated into the design of a different system of sensors. The suggested circuit in this case study is categorized by high dynamic range, low rate of power consumption as well as variable sensing range. With the aforementioned features of the circuit, it hence promotes easy to use userinterface and is also having low cost at the same time[ CITATION Eri13 \l 1033 ]. The novel realization of a synchronous demodulation mechanism is one of the well-known interface circuits which is employed in this case study. Low power consumption of this portable sensing system is the most design standards considered for the designer[ CITATION Den13\l 1033 ]. This circuit employs the use of a switch based capacitance to voltage converter is fabricated and designed in 0.35μm using CMOS technique and it consumes a very low power of about 600μW. The circuit used in this case study is able to detect a very low capacitance of about 1pF. The suggested circuit in this case study is tested with several types of sensors including motion, humidity, and variable MEMS capacitors. Capacitive sensors basically are employed to help sense a change in distance (motion) and also a chemical stimulus[ CITATION Dan131 \l 1033 ]. Introduction
ANALOG ELECTRONICS 3Creating (MOS) Metal Oxide Semiconductor transistor (one of the essential building blocks) in the current electronic devices is one of the major achievements in the field of electronic engineering in the 20th century[ CITATION Ron13 \l 1033 ]. Over past few years, gradual transistor miniaturization has resulted in the integration of huge electronic components to very small devices in a single chip. Fabrication technologies for these IC later improved and were used to build very small features making these ICs to be very small until they can challenge human naked eyes[ CITATION Jos12 \l 1033 ]. The normal operation of a synchronous demodulation has been tried by constructing a prototype (a typical example) on a PCB (printed- circuit board). This is tailored for hand gesture observing for user electronic components like mobile phones. To enable expansion of the dynamic circuit range a new response mechanism is put to theinitial circuit. In this our case study, the circuit was designed in exactly 0.35μm CMOS mechanism and it was then tried using a humidity sensor[ CITATION SMS12 \l 1033 ]. The rate of power consumption is a very vital criterion in this design and it is highly monitored and it is reduced further by using an interface circuit with charge transfer mechanism. In our case study design, a converter of a capacitance to pulse width is constructed with the help of building blocks[ CITATION Jam136 \l 1033 ]. The designed circuit was then fabricated in 0.35μm by the help of the CMOS technology which makes it easier to build this circuit in a small single chip. The resultant small chip circuit was tested with a variable MEMS capacitor and a position sensor. Literature Review Capacitive sensing
ANALOG ELECTRONICS 4This micro sensor sense variation of chemical and physical stimulus, it achieves this by detecting the change in dielectric properties or sometimes displacement properties of a solid material. A lot of consideration is take in the designing of the structure of this sensing element todetermine how the stimulus impact on capacitance value. The vital concepts of the capacitive sensors are illustrated further as below;The basic configuration of capacitive sensors.A meek configuration of this sensor is to have two electrodes which are parallel to one another having a distance of g between them and an overlapping cross sectional area A[ CITATION Cre11 \l 1033 ]. Then we obtain the capacitance of this circuit as below; . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I Where; £0 is taken as vacuum’s permittivity, £r is dielectric relative permittivity between the two parallel electrodes. Capacitive sensing based on variation in the gap. The most common method of capacitive sensing is grounded on varying the plate’s distance of separation g. And this is easily analyzed from the fact that the separation gap is inversely proportional to the capacitance. When the impedance of the capacitor is taken the behavior is linear but the output will be nonlinear if a direct measurement of the capacitance is taken[ CITATION Bar111 \l 1033 ]. Thus the direct measurement always needs further conditioning of the signal to help compensate for that reciprocal (the inverse proportionality) between the motion of the electrodes and the capacitance. The diagram of this setup can be illustrated in the figure below:
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