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Analysis of differential amplifier with active load

Include Synonyms Include Dead terms. Peer reviewed Direct link. A differential amplifier composed of an emitter-coupled pair is useful as an example in lecture presentations and laboratory experiments in electronic circuit analysis courses. However, in an active circuit with zero input load V[subscript id], both laboratory measurements and PSPICE and LTspice simulation results for the output voltage V[subscript o] are considerably lower than one base emitter unit V[subscript BE on ] below the supply voltage V[subscript CC], as predicted by a textbook derivation.


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Design and Analysis of High Gain Differential Amplifier Using Various 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 Gain-Bandwidth 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. The design is implemented using cadenceEDA environment and simulated using Analog design environment. 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. 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.

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. Different types of differential amplifiers are studied, designed and analyzed in terms of its performance. A comparison is made to analyze the circuit by varying the design parameters.

Fig 1. Basic differential amplifier with passive load. The resistors RD are used as load to drive the transistors into saturation. The two input voltages Vin1 and Vin2 are applied at the gate terminal of the MOS transistors, which are equal in magnitude and opposite in phase. The output voltage is measured across two nodes X and Y. The differential signal is measured between these nodes which have equal magnitude and opposite phase to the inputs.

The major advantage of this circuit is it has greater output voltage swing. When two inputs Vin1 and Vin2 are applied with same magnitude and same phase i. If suppose the value of Vin,CM is low then it may turn off M1 and M2, hence no amplification but the output will be clipped off. Hence a minimum bias current is required to maintain the common mode level.

The problem of biasing is overcome by using a constant current source Iss in the circuit. The circuit shown in fig 2 uses a constant current source which is used to maintain a minimum bias current and also to avoid the effects of the common mode level changes in the output.

In this circuit the ideal current source is replaced by a transistor driven a constant voltage source and operated in saturation region and hence it acts as a constant current source. Fig2 : Differential Amplifier with Current Source. Here the circuit is designed by using different load using active components and they can be like diode-connected or current source loads.

The diode connected load has an advantage of overcoming the problem of lowering the voltage swing and effect on gain due to common mode. In this circuit we use PMOS transistors as load by selecting proper dimensions and proper bias current. In this circuit we replace the resistors by active devices NMOS M3 and M4 and driven by external source to be in saturation. The external bias affects the trans conductance of M1 and M2, so to avoid this effect the tail current by Iss is set properly.

We conclude that for. In this circuit the external biasing is removed and a differential pair with current mirror is configured as active load.

The main purpose of this configuration is it converts a fully differential input to single-ended output. Here the transistors T3 and T4 are similar to each other.

This is done due to the reduced drain current of T2 and increased drain current of T4. The T4 and T2 are paired such that T4 helps T2 for a change in output voltage. The frequency response of the basic differential amplifier and other circuits are presented. The magnitude and phase response are shown, and single side output voltage gain is measured. The design was implemented using cadence EDA tool, nm technology.

A detailed analysis like DC, transient and AC analysis are done and a comparison is made for all the circuits. In this paper, the different topologies of differential amplifiers have been designed and analyzed in terms of gain, gain bandwidth product, and CMRR. The designs are operated at 1. EE Term Project Report. Roberts, Sackinger andW. Grasso and S. ABSTRACT: In conventional boost converter like switched capacitor converter, switched inductor converter, cascaded boost converter maximum voltage gain is limited due to extreme duty.

Here a linear buck converter is designed and developed using the LM voltage regulator with a variable input voltage of V and constant output voltage of 5V.. The fuzzy inference system combines fuzzy IF—THEN rules for mapping from fuzzy sets in the input space X to the output space Y based on fuzzy logic principle.. In fuzzy.

In this work, an asymmetrical differential input circuit with active DC offset rejection circuit was implemented to minimize the systematic offset of the amplifier..

This paper represents a comparative study of three types of dynamic latched comparators in terms of offset voltages, speed , stability and power working in nm CMOS. The closed loop control of output voltage is done using fuzzy controller.. The performance of the controller is. In these proposed Sense Amplifiers which are as shown in Figure 3 and Figure 4, a latch is used as a load in the first stage for a large differential voltage for the second stage. Although some high performance current mirrors such as cascode, regulated cascade, and low voltage regulated cascode current mirrors can be used instead of simple one to improve the.

Like phase shifted pulse width modulation, in level shifted pulse width modulation more than one carrier signal is used to generate the multilevel voltage waveform.. Show more 4 Page. Show more Page. Download now 5 Page. Fig3: Differential amplifier with active load In this circuit we replace the resistors by active devices NMOS M3 and M4 and driven by external source to be in saturation.

Fig 5: Basic Differential amplifier Circuit with passive load. Fig 6: Transient Response of the basic Differential Amplifier. Fig Differential Amplifier with Diode Connected topology. Read more. Figure Fig 1. References Updating Download PDF - 5 Page - 1.

Related documents. Synthesis of the Output Voltage for Multilevel Inverters. Design and analysis of a novel multi input multi output high voltage DC transfor Analysis and Design of a Low offset high speed and low voltage double tail compa Voltage Range. Show more.


What is the voltage gain of differential amplifier with active load?

Electrical Engineering Stack Exchange is a question and answer site for electronics and electrical engineering professionals, students, and enthusiasts. It only takes a minute to sign up. Connect and share knowledge within a single location that is structured and easy to search. I completed the theoretical parts of DC and AC analysis.

transient analysis doesn't show the beginning of the The source cross-coupled differential amplifier with active loads is shown in Fig.

Active load


Skip to Main Content. A not-for-profit organization, IEEE is the world's largest technical professional organization dedicated to advancing technology for the benefit of humanity. Use of this web site signifies your agreement to the terms and conditions. Analysis of the CMOS differential amplifier with active load and single-ended output Abstract: The CMOS differential amplifier with active load and single-ended output is one of the most popular circuits used in analog and mixed signal applications owing to its amazing performances. Very often the analysis of the differential amplifier is simplified and its behaviour is not explained properly. In this paper the facts that the gate to source voltages and the current changes of the output transistors in the differential mode are not of equal amount are explained. The body-effect is also included into the analysis. Article :.

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analysis of differential amplifier with active load

Skip to Main Content. A not-for-profit organization, IEEE is the world's largest technical professional organization dedicated to advancing technology for the benefit of humanity. Use of this web site signifies your agreement to the terms and conditions. Analysis of the differential amplifier with an active load Abstract: The analysis and simulation of an emitter coupled differential amplifier with an active load is presented. In most books, the two halves of the differential amplifier are assumed to be identical.

Differential amplifiers are the basic building block in the analog circuit design.

L35. Differential Amplifier BJT Diff Amp with Active Load Small ...


Differential amplifier. The function of a differential amplifier is to amplify the difference between two signals. The need for differential amplifier arises in many physical measurements where response from DC to many MHz of frequency is required. This forms the basic input stage of an integrated amplifier. The basic differential amplifier has the following important properties of.

1.6: The Differential Amplifier

Forgot Password. Forgot User Name. Sign up. Basic Electronics View More Bodhbridge btechguru. Fully Differential Single Stage Opamp. Semiconductor Materials: Intrinsic and Extrinsic.

Fig3: Differential amplifier with active load. In this circuit we replace the resistors by active devices (NMOS) M3 and M4 and driven by external source to.

EE 420L Electronics II Laboratory Laboratory Exercise #6 Differential

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Active load is primarily used in the collector of the differential amplifier of an OPAMP


In this post, differential amplifier using BJT and differential amplifier using op-amps are explained in detail. Please go through both of them to get a better understanding. The circuit diagrams and detailed equations are provided along with the article. Please go through them. A differential amplifier is designed to give the difference between two input signals. The circuit is shown below.

The circuit diagram of a differential amplifier using one opamp is shown below. BJT Differential Amplifier using active loads: A simple active load circuit for a differential amplifier is the current mirror active load as shown in figure.

Lecture 13 MOSFET Differential Amplifiers Microelectronic circuits by

Most modern operational amplifiers utilize a differential amplifier front end. In other words, the first stage of the operational amplifier is a differential amplifier. This circuit is commonly referred to as a diff amp or as a long-tailed pair. A diff amp utilizes a minimum of 2 active devices, although 4 or more may be used in more complex designs. Our purpose here is to examine the basics of the diff amp so that we can understand how it relates to the larger operational amplifier. Therefore, we will not be investigating the more esoteric designs.

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