International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395 -0056
Volume: 04 Issue: 05 | May -2017
p-ISSN: 2395-0072
www.irjet.net
Design and Analysis of High Gain Differential Amplifier Using Various Topologies SAMARLA.SHILPA1, J SRILATHA2 1Assistant
Professor, Dept of Electronics and Communication Engineering, NNRG, Ghatkesar, Hyderabad, India. Dept of Electronics and Instrumentation Engineering, CVRCE, Ibrahimpatnam, Hyderabad, India. ---------------------------------------------------------------------***--------------------------------------------------------------------1.1 Differential Amplifier Abstract - The objective of this paper is to design a 2
differential amplifier using different topologies. Differential amplifiers are the basic building block in the analog circuit design. The characteristics of the differential amplifier are measured by Gain, Common mode Rejection Ratio, and GainBandwidth product. In this paper a high performance differential amplifiers are designed using different approaches and a comparison is made between them. A low pass filter is designed using a differential amplifier. This work presents the optimized architecture of a differential amplifier. The simulation results are verified by using virtuoso 6.1, 0.18um technology at supply voltage 1.8v. The design is implemented using cadenceEDA environment and simulated using Analog design environment. Key Words: Differential Amplifier, Low Voltage and High Gain, CMRR. 1. INTRODUCTION Over the past few years, the electronics industry has made tremendous changes in the in the era of VLSI technology. The major changes came through in the market are due to the invention of MOS transistors. Integration of IC’s from small scale, medium scale, large scale to over ultra large scale integration has lead many changes in the electronic industry. It consists of mainly memory, small or micro and logic sales, has contributed a worldwide sales of approximately 75% with the MOS transistors, which enhances the strength of CMOS technology. CMOS technology involves in mainly satisfying all the design constraints like power, area, and speed by minimizing the feature size and using the optimization techniques by lowering the supply voltage, using VTCMOS and MTCMOS etc. CMOS technology has more advantage than an NMOS technology design due to the design flexibility and easily configurable. Hence CMOS has got a rapid acceptance in the upcoming technology in the area of analog, digital and mixed integrated circuits, like RF communication field, signal processing and biomedical applications etc.
Š 2017, IRJET
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The differential amplifier is the most important block in designing any analog circuit. The differential amplifiers are designed using bipolar transistors and MOS transistors. An amplifier is a circuit that amplifies any weak signal and strengthens it which is used mainly in communication to transmit a signal over long distance and the signal may be analog or digital. A differential amplifier circuit amplifies the difference of any two input signals and rejects any two common signals. The ideal characteristics of an amplifier are infinite gain, infinite bandwidth and infinite common mode rejection ratio, high input impedance and low output admittance, less distortion, sensitivity. Also it has less harmonic distortion and increased output voltage swing and the performance of the circuit is measured by its characteristics. Differential amplifiers are widely used due to less distortion in the output and are widely used in linear amplification circuits. A differential amplifier can be designed in many ways where the output may be single ended or double ended. The most commonly used amplifier is double ended means which has two inputs and which gives two outputs and is commonly known as fully differential amplifier. The advantages of fully differential amplifier over single ended are simple biasing, high immunity to noise, and high linearity. But the disadvantage is large area. The fully differential amplifier amplifies the difference of two input signals which are out of phase and rejects the signals which have common phase due to any noise induced. This is measured or termed as common mode rejection ratio (CMRR) and its offset voltage. An ideal amplifier circuit has infinite CMRR. A feedback circuit like common mode feedback circuit is used at the output of the amplifier which is used to adjust the bias current and hence rejects the common mode signals. Two types of offset voltages input offset voltage and output offset voltage, the output offset voltage is defined as the difference between the final output voltage to the ideal output voltage when a common signal is applied at both the ends of inputs, similarly when the output offset voltage is divided by the differential voltage gain then it is termed as input offset voltage. ISO 9001:2008 Certified Journal
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