Op amp level shifter amplifier classes
An electronic amplifier , amplifier , or informally amp is an electronic device that increases the power of a signal. It does this by taking energy from a power supply and controlling the output to match the input signal shape but with a larger amplitude. In this sense, an amplifier modulates the output of the power supply. Numerous types of electronic amplifiers are specialized to various applications. An amplifier can refer to anything from a electrical circuit that uses a single active component, to a complete system such as a packaged audio hi-fi amplifier.
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What is an IC 741 Op Amp : Pin Diagram & Its Working
A class AB operational amplifier includes an input stage, an output stage and a level shifter stage to control the quiescent current of the output stage and to transfer the signal from the input stage to the output stage, and a control circuit of the level shifter stage. The control circuit includes a transistor differential pair having a differential input terminals and the differential voltage at the differential terminals of the differential pair controls the level shifter stage.
The present invention is a continuation of U. The present invention relates to a high performance class AB operational amplifier.
The design of high-accuracy analogue circuits is becoming a difficult task with the scaling down of supply voltages and transistor channel lengths of the current mixed-signal integrated circuits. Most of these circuits require the use of high performance active cell: the operational amplifier OpAmp. Furthermore, some low-IF transceivers make use of complex filters which require operational amplifier with a very high gain-bandwidth product in order to have enough loop gain at the higher band limit.
Ultra low power circuit imposes a current reduction in order to increase the battery life-time in mobile handsets. The class-AB output stage topology allows driving a large load capacitor with a small output stage bias current. Despite to its property, the most important problem designing class AB OpAmps is the accurate control of the output current which depends on process and supply voltage variations.
To solve this problem it is necessary to introduce control circuits. The drain terminals of the transistor of the differential pair are connected to the output terminals OUT P , OUT M by means of the compensation network constituted of a series of a capacitor C c and a resistance R c.
The circuit in FIG. A practical implementation of the circuit in FIG. The gate terminals of the transistors M 5a , M 5b are connected to the output terminals of the differential pair while the gate terminals of the transistors M 4a , M 4b are connected to the bias voltage VB p. The circuit topology in FIG. Unfortunately, this topology has many drawbacks to be solved; the output-stage current is not controlled and depends on the process, mismatch of the MOS transistors and on the supply voltage.
Furthermore, this topology is not at low voltage. Another circuit topology used is shown in FIG. This circuit solution comprises the use of a circuit 1 to control the output current Iout of the class AB output stage in FIG.
The gate terminal of the transistor M 4 is not connected with the bias voltage VB P but with the circuit 1 , more precisely the gate terminal of the transistor M 4 is connected with the gate terminal and the drain terminal of a PMOS transistor M 4r and with the gate terminal of a PMOS transistor M 3r so that the transistor M 4r and M 3r form a current mirror.
Another current mirror comprises the transistor M 1r and M 6r adapted to mirror the bias current I B in the PMOS transistor M 7r having the gate terminal connected with the drain terminal of the transistor M 31 and with the source terminal of a PMOS transistor M 5r the drain terminal of which is connected to ground GND and the gate terminal is connected with the gate terminal of the transistors M 7r and M 6r.
Loop consists of transistors M 3r , M 7r , M 2r and M 4r. The gate-source voltage of the transistor M 5r will be adjusted corresponding to the currents flowing through the transistors M 7r and M 6r The current flowing through the transistor M 5r is copied in the transistor M 4 by the transistor M 3r and the gate-source voltage of the transistor M 5 is adjusted to a right level forcing the output stage current to the controlled level.
Aslanzadeh, S. Mehrmanesh, M. Vahidfar, A. This solution is not suitable for very low current consumption application; in the case of low bias current the output current depends on the process variation of the transistor and the performances of the class AB output stage of the operational amplifier are reduced. In view of the state of the art, the object of the present invention is to provide a high performance class AB operational amplifier which overcomes the above-mentioned drawbacks. According to the present invention, this object is achieved by means of a class AB operational amplifier comprising an input stage, an output stage and a level shifter stage adapted to control the quiescent current of the output stage and to transfer the signal from the input stage to the output stage, a control circuit of the level shifter stage, characterized in that the control circuit comprises at least one transistor differential pair having differential input terminals, said control circuit being configured so that the differential voltage at the differential terminals of the transistor differential pair controls the level shifter stage.
The features and advantages of the present invention will become apparent from the following detailed description of an embodiment thereof, illustrated only by way of non-limitative example in the annexed drawings, in which:. The operational amplifier comprising an input stage 10 , an output stage 11 , a level shifter stage 12 adapted to control the bias current of the output stage and to transfer the signal from the input stage to the output stage, a control circuit 13 of the level shifter stage.
Specifically, FIG. The input stage 10 , similar to the input stage 1 in FIG. The output stage 11 comprises a couple of a first M 6 and a second M 7 output transistors, in series to each other, and arranged between a first voltage reference Vdd and a second voltage reference GND and being interconnected at an output terminal OUT of the operational amplifier; the first output transistor has a control terminal connected to an output terminal of the input stage The level shifter stage 12 comprises a couple of a first M 5 and a second M 9 intermediate transistors, connected in series to each other by means of an impedance, that is the parallel of a resistance R and a capacitor C, and coupled between a first voltage reference Vdd and a second voltage reference GND; specifically, the transistors of the level shifter stage 12 are MOS transistors and the source terminal A of the first transistor M 5 is coupled with the drain terminal B of the second transistor M 9 by means of the parallel of the resistance R and the capacitor C.
The first intermediate transistor M 5 has the control terminal connected with one output terminal of the input stage 10 and the second intermediate transistor M 9 has the output terminal connected with the control terminal of the second output transistor M 7 ; the second intermediate transistor M 9 has the control terminal connected to an output terminal of a control circuit The second intermediate transistor acts as a current generator.
Particularly, the level shifter stage 12 fixes the voltage V A while the voltage V B is varied by the control circuit The control circuit 13 comprises replica circuits based on transistors M 7r , M 6r and M 5r. This ratio of current in the stages 10 , 11 and 12 and in the replica-circuit branches is configured to reduce the current consumption of the control circuit The currents of the transistors M 7r , M 6r and M 5r are fixed through current sources to a scaled value of the desired current flowing through the transistors M 7 , M 6 and M 5.
This allows to evaluate the desired voltage on the node A and B with process and temperature variations. The control circuit 13 comprises first and second circuit branches 14 , 15 respectively formed by the transistor M 7r wherein the bias current Ioutr flows, and by the transistor M 6r wherein the bias current Ioutr flows and the transistor M 5r having the gate terminal connected with the gate terminal and with the drain terminal of the transistor M 6r.
A transistor M 9r forms a mirror with the transistor M 9 of the level shifter stage. The transistor M 9r has the gate and the drain terminals connected with the drain terminal of the transistor M 8a ; another transistor M 9r has the gate and the drain terminals connected only with the drain terminal of the transistor M 8b.
This current is mirrored in the transistor M 9 with a mirror factor k. The voltage V A is given by the sum of the gate-source voltages of the transistors M 6 and M 5 , that is. This configuration has the advantage to eliminate the dependency of the output stage quiescent current on transistor process variation and supply voltage while controlling this current in an open loop manner which does not affect the frequency response and stability of the amplifier.
These curves show a perfect two pole system. The operational amplifier exhibits a DC gain G of 50 dB and a unity-gain frequency of MHz and 60 degree of phase margin.
The montecarlo simulations show a very accurate control of the output-stage current. As above mentioned FIG. While the invention has been described by way of example and in terms of the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments.
To the contrary, it is intended to cover various modifications and similar arrangements as would be apparent to those skilled in the art. Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements. The operational amplifier according to claim 1, wherein said control circuit comprises circuitry coupled with the input terminals of the differential pair of transistors and wherein a first bias current flows, the control circuit being configured to control the quiescent current to be proportional to the amount of said first bias current.
The operational amplifier according to claim 2, wherein said circuitry of the control circuit comprises a first and a second circuit branch connected with the respective input terminals of the differential pair of transistors, said circuit branches being a replica circuit of the two circuit branches of the output stage and the level shifter stage which are connected at the respective terminals of the impedance.
The operational amplifier according to claim 2, wherein said differential pair of transistors comprises a MOS transistor and a resistance arranged between the source terminals of the differential pair of transistors, said impedance comprising a further resistance and said resistance being proportional to the further resistance, said differential pair of transistors being configured so that the voltage across the resistance is the differential voltage at the differential terminals of the differential pair of transistors.
The operational amplifier according to claim 4, wherein said control circuit comprises a first transistor forming with an intermediate transistor of the level shifter stage a current mirror to mirror the current flowing through the differential pair of transistors into the level shifter stage, said first transistor being a replica of said intermediate transistor.
The class AB operational amplifier of claim 1 further comprising an additional input stage, output stage, level shifter stage, and control circuit. The class AB operational amplifier of claim 7 wherein the differential pair of transistors comprises PMOS transistors.
The class AB operational amplifier of claim 7 wherein the output stage comprises a first transistor and a second transistor, in series connection. The class AB operational amplifier of claim 9 wherein a series-connected resistor and capacitor are coupled between a gate and a drain of the second transistor.
The class AB operational amplifier of claim 7 wherein the level shifter stage comprises a first transistor and a second transistor, coupled together by an impedance. The class AB operational amplifier of claim 12 wherein the impedance comprises a resistor and a capacitor in parallel. The class AB operational amplifier of claim 12 wherein an intermediate node between the first transistor and the impedance is coupled to ground.
The class AB operational amplifier of claim 7 further comprising a first circuit branch and a second circuit branch coupled to the differential pair of transistors. SUMMARY OF THE INVENTION According to the present invention, this object is achieved by means of a class AB operational amplifier comprising an input stage, an output stage and a level shifter stage adapted to control the quiescent current of the output stage and to transfer the signal from the input stage to the output stage, a control circuit of the level shifter stage, characterized in that the control circuit comprises at least one transistor differential pair having differential input terminals, said control circuit being configured so that the differential voltage at the differential terminals of the transistor differential pair controls the level shifter stage.
A class AB operational amplifier comprising: an input stage; an output stage; and a level shifter stage and a control circuit coupled thereto and configured to control a quiescent current of the output stage and to transfer a signal from the input stage to the output stage, the control circuit comprising a differential pair of transistors having differential input terminals, an impedance, first and second intermediate transistors coupled in series by the impedance and arranged between a first and a second reference voltage, and the impedance having a voltage thereacross being a differential voltage at the differential input terminals that controls the level shifter stage.
A class AB operational amplifier comprising: an input stage having a differential pair of transistors; an output stage; a level shifter stage to control the bias current of the output stage and to transfer the signal from the input stage to the output stage; and a control circuit coupled to the level shifter stage, wherein the control circuit comprises replica transistors from the level shifter stage and the output stage, and generates a replica output current from the output stage.
A class AB operational amplifier comprising: two symmetrical circuits, each circuit comprising: an input stage; an output stage; a level shifter stage to control the bias current of the output stage and to transfer the signal from the input stage to the output stage; an impedance; first and second intermediate transistors coupled in series by the impedance and arranged between a first and a second reference voltage; and a control circuit coupled to the level shifter stage, wherein the control circuit comprises replica transistors from the level shifter stage and the output stage, and generates a replica output current from the output stage.
Referenced Cited. Patent Documents September 24, Sotelo et al. Patent History. Current U. Justia Legal Resources. Find a Lawyer. Law Students. US Federal Law. US State Law. Other Databases. Marketing Solutions.
For which of the following reasons, DC level shifting is required in op-amps
Operational Amplifier, also called as an Op-Amp, is an integrated circuit, which can be used to perform various linear, non-linear, and mathematical operations. An op-amp is a direct coupled high gain amplifier. You can operate op-amp both with AC and DC signals. This chapter discusses the characteristics and types of op-amps. An op-amp consists of differential amplifier s , a level translator and an output stage. A differential amplifier is present at the input stage of an op-amp and hence an op-amp consists of two input terminals.
Summing Amplifier
A class AB operational amplifier includes an input stage, an output stage and a level shifter stage to control the quiescent current of the output stage and to transfer the signal from the input stage to the output stage, and a control circuit of the level shifter stage. The control circuit includes a transistor differential pair having a differential input terminals and the differential voltage at the differential terminals of the differential pair controls the level shifter stage. The present invention is a continuation of U. The present invention relates to a high performance class AB operational amplifier. The design of high-accuracy analogue circuits is becoming a difficult task with the scaling down of supply voltages and transistor channel lengths of the current mixed-signal integrated circuits. Most of these circuits require the use of high performance active cell: the operational amplifier OpAmp. Furthermore, some low-IF transceivers make use of complex filters which require operational amplifier with a very high gain-bandwidth product in order to have enough loop gain at the higher band limit. Ultra low power circuit imposes a current reduction in order to increase the battery life-time in mobile handsets. The class-AB output stage topology allows driving a large load capacitor with a small output stage bias current. Despite to its property, the most important problem designing class AB OpAmps is the accurate control of the output current which depends on process and supply voltage variations.
Audio Op Amp
Amplifiers and Comparators Minimize menu. Please log in to show your saved searches. ST's operational amplifier portfolio provides a unique choice of high performance, low power, precision op amps and tiny packages. It addresses voltages from 1. Get instant access for free to our recorded webinar, covering:.
Power amplifier classes
An operational amplifier , often called an 'op-amp', is a DC-coupled high-gain electronic voltage amplifier with differential inputs and, usually, a single output. Typically the output of the op-amp is controlled either by negative feedback, which largely determines the magnitude of its output voltage gain, or by positive feedback, which facilitates regenerative gain and oscillation. High input impedance at the input terminals and low output impedance are typical characteristics. Op-amps are among the most widely used electronic devices, used in a vast array of consumer, industrial, and scientific devices. Modern designs are electronically more rugged than earlier implementations and some can sustain direct short-circuits on their outputs without damage. An op-amp, defined as a general-purpose, DC-coupled, high gain, inverting feedback amplifier , is first found in US Patent 2,, "Summing Amplifier" filed by Karl D.
Op Amps-Operational Amplifiers
An amplifier is a two-port electronic device used to amplify the signal or increase the power of a signal with the help of a power supply. The power is supplied through the input terminal of the amplifier. The output of the amplifier can be the increased amplitude, etc. The gain of the amplifier determines its amplification. It is the major factor that determines the output of a device. Amplifiers are used in almost every type of electronic component. The gain is calculated as the ratio of the output parameter power, current, or voltage to the input parameter. Amplifiers are used in various applications, such as automation, marine, sensors, etc.
3. The Typical Op-amp
The short form of the operational amplifier is op-amp, which is one kind of solid-state IC. The first operational amplifier is designed by Fairchild Semiconductors in the year It is the basic building block of analog electronic circuits that accomplish different types of analog signal processing tasks. These ICs use exterior feedback to regulate their functions and these components are used as a multipurpose device in various electronic instruments.
High performance class AB operational amplifier
RELATED VIDEO: lec-6 Level Shifter Circuit Op-Amp - Op-Amp - LICA - R K Classes - Hindi+Eng -Today, digital circuit cores provide the main circuit implementation approach for integrated circuit IC functions in very-large-scale integration VLSI circuits and systems. Typical functions include sensor signal input, data storage, digital signal processing DSP operations, system control and communications. Despite the fact that a large portion of the circuitry may be developed and implemented using digital logic techniques, there is still a need for high performance analogue circuits such as amplifiers and filters that provide signal conditioning functionality prior to sampling into the digital domain using an analogue-to-digital converter ADC for analogue sensor signals. The demands on the design require a multitude of requirements to be taken into account. In this chapter, the design of the operational amplifier op-amp is discussed as an important circuit within the front-end circuitry of a mixed-signal IC. The discussion will focus on the design of the op-amp using different compensation schemes incorporating negative Miller compensation and designed to operate at lower power supply voltage levels.
An operational amplifier often op amp or opamp is a DC-coupled high- gain electronic voltage amplifier with a differential input and, usually, a single-ended output. Operational amplifiers had their origins in analog computers , where they were used to perform mathematical operations in linear, non-linear, and frequency-dependent circuits. The popularity of the op amp as a building block in analog circuits is due to its versatility. By using negative feedback , the characteristics of an op-amp circuit, its gain, input and output impedance , bandwidth etc. Op amps are used widely in electronic devices today, including a vast array of consumer, industrial, and scientific devices. The op amp is one type of differential amplifier. Other types of differential amplifier include the fully differential amplifier similar to the op amp, but with two outputs , the instrumentation amplifier usually built from three op amps , the isolation amplifier similar to the instrumentation amplifier, but with tolerance to common-mode voltages that would destroy an ordinary op amp , and negative-feedback amplifier usually built from one or more op amps and a resistive feedback network.
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