Distributed amplifiers are a very resourceful example of distributed circuit design that incorporate transmission line theory into traditional amplifier design in order to arrive at an amplifier with a larger gain-bandwidth product than is realizable by conventional circuits. The process of circuit design can cover systems ranging from national power grids all the way down to the individual transistors within an integrated circuit. ... A transmission line is the material medium or structure that forms all or part of a path from one place to another for directing the transmission of energy, such as electromagnetic waves or acoustic waves, as well as electric power transmission. ... Gain bandwidth product for amplifier is a result of multiplication of product of gain, a constant for an amplifier, and designed bandwidth. ... There are many kinds of circuit An electric circuit interconnects electrical elements or electronic elements together usually to perform some useful function. ...

N Stage Traveling Wave Amplifier

History

The design of the distributed amplifiers was first formulated by William S. Percival in 1936 [1]. In that year Percival proposed a design by which the transconductances of individual vacuum tubes could be added linearly, thus arriving at a circuit that achieved a gain-bandwidth product greater than that of an individual tube. Percival's design did not gain widespread awareness however, until a publication on the subject was authored by Ginzton, Hewlett, Jasberg, and Noe in 1948 [2]. It is to this later paper that the term distributed amplifier can actually be traced. Traditionally, DA design architectures were realized using valve technology. Transconductance, also known as mutual conductance, is a property of certain electronic components. ... In electronics, a vacuum tube (U.S. and Canadian English) or (thermionic) valve (outside North America) is a device generally used to amplify, or otherwise modify, a signal by controlling the movement of electrons in an evacuated space. ... There are many kinds of circuit An electric circuit interconnects electrical elements or electronic elements together usually to perform some useful function. ... A valve is a device that regulates the flow of fluids (either gases, fluidised solids, slurries or liquids) by opening, closing, or partially obstructing various passageways. ...

Current technology

More recently, III-V semiconductor technologies, such as GaAs [3]-[5] and InP [6],[7] have been used. These have superior performance resulting from higher bandgaps (higher electron mobility), higher saturated electron velocity, higher breakdown voltages and higher-resistivity substrates. The latter contributes much to the availability of higher quality-factor (Q-factor or simply Q) integrated passive devices in the III-V semiconductor technologies. A semiconductor is a material with an electrical conductivity that is intermediate between that of an insulator and a conductor. ... In solid state physics and related applied fields, the band gap is the energy difference between the top of the valence band and the bottom of the conduction band in insulators and semiconductors. ... Properties The electron is a lightweight fundamental subatomic particle that carries a negative electric charge. ... Electrical resistivity (also known as specific electrical resistance) is a measure of how strongly a material opposes the flow of electric current. ... The Q factor or quality factor is a measure of the rate at which a vibrating system dissipates its energy into heat. ... Integration may be any of the following: Usually integration is the construction of an object, a theory, etc. ... Passive has several meanings: In grammar it describes a grammatical voice. ...

To meet the marketplace demands on cost, size, and power consumption of monolithic microwave integrated circuits (MMICs), research continues in the development of mainstream digital bulk-CMOS processes for such purposes. The continuous scaling of feature sizes in current IC technologies has enabled microwave and mm-wave CMOS circuits to directly benefit from the resulting increased unity-gain frequencies of the scaled technology. This device scaling, along with the advanced process control available in today's technologies, has recently made it possible to reach an fT of 170 GHz and a maximum oscillation frequency (fmax) of 240 GHz in a 90nm CMOS process [8]. Something that is monolithic is something created in one piece, resembling a monolith such as an obelisk. ... Microwave image of 3C353 galaxy at 8. ... An integrated circuit (IC) is a thin chip consisting of at least two interconnected semiconductor devices, mainly transistors, as well as passive components like resistors. ... A digital system is one that uses discrete numbers, especially binary numbers, or non-numeric symbols such as letters or icons, for input, processing, transmission, storage, or display, rather than a continuous spectrum of values (an analog system). ... A gigahertz is a billion hertz or a thousand megahertz, a measure of frequency. ... Oscillation is the periodic variation, typically in time, of some measure as seen, for example, in a swinging pendulum. ... Sine waves of various frequencies; the lower waves have higher frequencies than those above. ...

Theory of Operation

The operation of the DA can perhaps be most easily understood when explained in terms of the traveling wave amplifier (TWA). The DA consists of a pair of transmission lines with characteristic impedances of Z₀ independently connecting the inputs and outputs of several active devices. An RF signal is thus supplied to the section of transmission line connected to the input of the first device. As the input signal propagates down the input line, the individual devices respond to the forward traveling input step by inducing an amplified complementary forward traveling wave on the output line. This assumes the delays of the input and output lines are made equal through selection of propagation constants and lengths of the two lines and as such the output signals from each individual device sum in phase. Terminating resistors Z_g and Z_d are placed to minimize destructive reflections. A transmission line is the material medium or structure that forms all or part of a path from one place to another for directing the transmission of energy, such as electromagnetic waves or acoustic waves, as well as electric power transmission. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... The term input has a variety of uses in different fields. ... // Information processing In information processing, output is the process of transmitting information by an object (verb usage). ... An electrical circuit consists of various components or devices or elements, which may be active or passive. ... The word propagation can mean: Multiplication or increase, as by natural reproduction. ... The word propagation can mean: Multiplication or increase, as by natural reproduction. ... Phase is an overloaded word used for: instantaneous phase: the current position in the cycle of something that changes cyclically phase shift: a constant difference/offset between two instantaneous phases, particularly when one is a standard reference Waves are amplitudes that change cyclically, often modeled as sinusoidal functions of time... Look up reflection in Wiktionary, the free dictionary. ...

The transconductive gain of each device is g_m and the output impedance seen by each transistor is half the characteristic impedance of the transmission line. So that the overall voltage gain of the DA is: In electronics, gain is usually taken as the mean ratio of the signal output of a system to the signal input of the system. ... In electrical engineering, Impedance is a measure of opposition to a sinusoidal electric current. ... Assorted transistors The transistor is a solid state semiconductor device that can be used for amplification, switching, voltage stabilization, signal modulation and many other functions. ...

,

where n is the number of stages.

Neglecting losses, the gain demonstrates a linear dependence on the number of devices (stages). Unlike the multiplicative nature of a cascade of conventional amplifiers, the DA demonstrates an additive quality. It is this synergistic property of the DA architecture that makes it possible for it to provide gain at frequencies beyond that of the unity-gain frequency of the individual stages. In practice, the number of stages is limited by the diminishing input signal resulting from attenuation on the input line. Means of determining the optimal number of stages are discussed below. Bandwidth is typically limited by impedance mismatches brought about by frequency dependent device parasitics. In its simplest form, multiplication is a quick way of adding identical numbers. ... A cascade is a term for a waterfall, or series of waterfalls, and is applied abstractly to many different concepts involving a series of steps or effects that follow one after the other. ... For the British rock band of the same name, see Amplifier (band) An amplifier can be considered to be any device that uses a small amount of energy to control a source of a larger amount of energy, although the term today usually refers to an electronic amplifier. ... Look up Additive in Wiktionary, the free dictionary When used as a noun, additive refers to something that is introduced to a larger quantity of something else, usually to alter characteristics of the larger quantity. ... This page is a candidate to be copied to Wiktionary. ... Sine waves of various frequencies; the lower waves have higher frequencies than those above. ... Bandwidth is a measure of frequency range, measured in hertz, of a function of a frequency variable. ... In electrical engineering, Impedance is a measure of opposition to a sinusoidal electric current. ... A parasite is an organism that lives in or on the living tissue of a host organism at the expense of it. ...

The DA architecture introduces delay in order to achieve its broadband gain characteristics. This delay is a desired feature in the design of another distributive system called the distributed oscillator. Delay is: In sound effects, any of a class of effect that adds one or more delayed versions of the original signal, to create effects such as echo or flanger. ... Broadband in general electronics and telecommunications is a term which refers to a signal or circuit which includes or handles a relatively wide range of frequencies. ...

References

• [1] W. S. Percival, “Thermionic Valve Circuits,” British Patent Specification no. 460,562, filed 24 July 1936, granted January 1937.
• [2] E. L. Ginzton, W. R. Hewlett, J. H. Jasberg, and J. D. Noe, “Distributed Amplification,” Proc. IRE, pp. 956-69, August 1948.
• [3] E. W. Strid and K. R. Gleason, “A DC-12 GHz Monolithic GaAsFET Distributed Amplifier,” IEEE Trans. Microwave Theory and Techniques, vol. MTT-30, no. 7, pp. 969-975, July 1982.
• [4] Y. Ayasli, R. L. Mozzi, J. L. Vorhaus, L. D. Reynolds, and R. A. Pucel, “A Monolithic GaAs 1-13-GHz Traveling-Wave Amplifier,” IEEE Trans. Microwave Theory and Techniques, vol. MTT-30, no. 7, pp. 976-981, July 1982.
• [5] K. B. Niclas, W. T. Wilser, T. R. Kritzer, and R. R. Pereira, “On Theory and Performance of Solid-State Microwave Distributed Amplifiers,” IEEE Trans. Microwave Theory and Techniques, vol. MTT-31, no. 6, pp. 447-456, June 1983.
• [6] R. Majidi-Ahy, C. K. Nishimoto, M. Riaziat, M. Glenn, S. Silverman, S.-L. Weng, Y.-C. Pao, G. A. Zdasiuk, S. G. Bandy, and Z. C. H. Tan, “5-100 GHz InP Coplanar Waveguide MMIC Distributed Amplifier,” IEEE Trans. Microwave Theory and Techniques, vol. MTT-38, no. 12, December 1990.
• [7] S. Kimura, Y. Imai, Y. Umeda, and T. Enoki, “Loss-compensated Distributed Baseband Amplifier for Optical Transmission Systems,” IEEE Trans. Microwave Theory and Techniques, vol. MTT-44, no. 10, pp. 1688-1693, October 1996.
• [8] D. Linten, S. Thijs, W. Jeamsaksiri, J. Ramos, A. Mercha, M. I. Natarajan, P. Wambacq, A. J. Scholten, and S. Decoutere, “An Integrated 5 GHz Low-Noise Amplifier with 5.5 kV HBM ESD protection in 90 nm RF CMOS,” 2005 Symp. on VLSI Circuits Digest of Technical Papers, pp. 86-89, July 16-18 2005.

External Links

• Microwaves101.com - Distributed amplifiers