RF power amplifier

<h2 id="amplifier-classes">Amplifier classes</h2>
Main article: <a href="/facts/Power_amplifier_classes/ocDIVQ73">Power amplifier classes</a>
The operation of RF amplifier circuits is classified based on the proportion of the cycle of the sinusoidal radio signal the amplifier (transistor or vacuum tube) where current is conducting. <a href="/facts/Power_amplifier_classes/ocDIVQ73">Class-A</a>, <a href="/facts/Power_amplifier_classes/ocDIVQ73">class-AB</a> and <a href="/facts/Power_amplifier_classes/ocDIVQ73">class-B</a> are considered the linear amplifier classes in which the active device is used as a controlled current source, while <a href="/facts/Power_amplifier_classes/ocDIVQ73">class-C</a> is a nonlinear class in which the active device is used as a switch. The <a href="/facts/Bias_(electrical_engineering)/lK0e6hbK">bias</a> at the input of the active device determines the class of the amplifier.
A common trade-off in power amplifier design is the trade-off between efficiency and linearity. The previously named classes become more efficient, but less linear, in the order they are listed. Operating the active device as a switch results in higher efficiency, theoretically up to 100%, but lower linearity.<a class="footnote-ref" id="fnref:2" href="#fn:2">2</a> Among the switch-mode classes are <a href="/facts/Class-D_amplifier/s5yyWFmo">class-D</a>, <a href="/facts/Power_amplifier_classes/ocDIVQ73">class-E</a> and <a href="/facts/Power_amplifier_classes/ocDIVQ73">class-F</a>.<a class="footnote-ref" id="fnref:3" href="#fn:3">3</a> The class-D amplifier is not often used in RF applications because the finite switching speed of the active devices and possible charge storage in saturation could lead to a large I-V product,<a class="footnote-ref" id="fnref:4" href="#fn:4">4</a> which deteriorates efficiency.

<h2 id="solid-state-vs-vacuum-tube-amplifiers">Solid state vs. vacuum tube amplifiers</h2>
Modern RF power amplifiers use <a href="/facts/Power_semiconductor_device/5c22S6E6">solid-state devices</a>, predominantly <a href="/facts/MOSFET/eTDJT2Km">MOSFETs</a> (metal–oxide–semiconductor field-effect transistors).<a class="footnote-ref" id="fnref:5" href="#fn:5">5</a><a class="footnote-ref" id="fnref:6" href="#fn:6">6</a><a class="footnote-ref" id="fnref:7" href="#fn:7">7</a> The earliest MOSFET-based RF amplifiers date back to the mid-1960s.<a class="footnote-ref" id="fnref:8" href="#fn:8">8</a> <a href="/facts/Bipolar_junction_transistor/9BMcGv5Q">Bipolar junction transistors</a> were also commonly used in the past, up until they were replaced by <a href="/facts/Power_MOSFET/rfT6MMTf">power MOSFETs</a>, particularly <a href="/facts/LDMOS/kofkoEMt">LDMOS</a> transistors, as the standard technology for RF power amplifiers by the 1990s,<a class="footnote-ref" id="fnref:9" href="#fn:9">9</a><a class="footnote-ref" id="fnref:10" href="#fn:10">10</a> due to the superior RF performance of LDMOS transistors.<a class="footnote-ref" id="fnref:11" href="#fn:11">11</a> Generally speaking, solid-state power amplifiers contain four main components: input, output, amplification stage and power supply.<a class="footnote-ref" id="fnref:12" href="#fn:12">12</a>
MOSFET transistors and other modern <a href="/facts/Solid-state_(electronics)/US0Qbq28">solid-state</a> devices have replaced <a href="/facts/Vacuum_tube/VHd1BNLq">vacuum tubes</a> in most electronic devices, but tubes are still used in some high-power transmitters (see <a href="/facts/Valve_RF_amplifier/6vh5WNRB">Valve RF amplifier</a>). Although mechanically robust, transistors are electrically fragile – they are easily damaged by excess voltage or current. Tubes are mechanically fragile but electrically robust – they can handle remarkably high <a href="/facts/Overvoltage/LsVwLvVQ">electrical overloads</a> without appreciable damage.

<h2 id="applications">Applications</h2>
The basic applications of the RF power amplifier include driving to another high-power source, driving a transmitting <a href="/facts/Antenna_(radio)/pGlcXBvc">antenna</a> and exciting <a href="/facts/Microwave_cavity/WY23zCqz">microwave cavity</a> resonators. Among these applications, driving transmitter antennas is most well known. The <a href="/facts/Transceiver/S6HSzRPf">transmitter–receivers</a> are used not only for voice and data communication but also for weather sensing (in the form of a <a href="/facts/Radar/jk9BTbFA">radar</a>).<a class="footnote-ref" id="fnref:13" href="#fn:13">13</a>
RF power amplifiers using <a href="/facts/LDMOS/kofkoEMt">LDMOS</a> (laterally diffused <a href="/facts/MOSFET/eTDJT2Km">MOSFET</a>) are the most widely used <a href="/facts/Power_semiconductor_device/5c22S6E6">power semiconductor devices</a> in <a href="/facts/Wireless_telecommunication/GfDoFwfo">wireless telecommunication</a> networks, particularly <a href="/facts/Mobile_network/8zA0jQJ9">mobile networks</a>.<a class="footnote-ref" id="fnref:14" href="#fn:14">14</a><a class="footnote-ref" id="fnref:15" href="#fn:15">15</a><a class="footnote-ref" id="fnref:16" href="#fn:16">16</a> LDMOS-based RF power amplifiers are widely used in digital mobile networks such as <a href="/facts/2G/4Xd52qkQ">2G</a>, <a href="/facts/3G/K1noBd8n">3G</a>,<a class="footnote-ref" id="fnref:17" href="#fn:17">17</a><a class="footnote-ref" id="fnref:18" href="#fn:18">18</a> and <a href="/facts/4G/Lfq6mSxl">4G</a><a class="footnote-ref" id="fnref:19" href="#fn:19">19</a> and the good cost/performance ratio make them the preferred option for <a href="/facts/Amateur_radio/cBsMyamV">amateur radio</a>.<a class="footnote-ref" id="fnref:20" href="#fn:20">20</a>

<h2 id="wideband-amplifier-design">Wideband amplifier design</h2>
<a href="/facts/Electrical_impedance/I06NSXtN">Impedance</a> transformations over large <a href="/facts/Bandwidth_(signal_processing)/7eMDzfJI">bandwidth</a> are difficult to realize, so conventionally, most <a href="/facts/Wideband/wv1yPnkF">wideband</a> <a href="/facts/Amplifier/pnRgxncC">amplifiers</a> are designed to feed a 50 Ω output load. <a href="/facts/Transistor/Bmr8zwL0">Transistor</a> output power is then limited to

P
          
            out
          
        
        ≤
        
          
            
              (
              
                V
                
                  br
                
              
              −
              
                V
                
                  k
                
              
              
                )
                
                  2
                
              
            
            
              8
              
                Z
                
                  o
                
              
            
          
        
        ,
      
    
    {\displaystyle P_{\text{out}}\leq {\frac {(V_{\text{br}}-V_{\text{k}})^{2}}{8Z_{\text{o}}}},}

where

V
 
 br
 
 
 
 
 {\displaystyle V_{\text{br}}}
 
 is defined as the <a href="/facts/Breakdown_voltage/pvggwv5h">breakdown voltage</a>,

V
          
            k
          
        
      
    
    {\displaystyle V_{\text{k}}}
  
 is defined as the knee voltage,

Z
 
 o
 
 
 
 
 {\displaystyle Z_{\text{o}}}
 
 is chosen so that the rated power can be met.
The external load is, by convention, 
 
 
 
 
 Z
 
 L
 
 
 =
 50
  
 Ω
 .
 
 
 {\displaystyle Z_{\text{L}}=50~\Omega .}
 
 Therefore, there must be some sort of <a href="/facts/Impedance_matching/0mdy9TAp">impedance matching</a> that transforms from 
 
 
 
 
 Z
 
 o
 
 
 
 
 {\displaystyle Z_{\text{o}}}
 
 to 
 
 
 
 
 Z
 
 L
 
 
 =
 50
  
 Ω
 .
 
 
 {\displaystyle Z_{\text{L}}=50~\Omega .}

The loadline method is often used in RF power amplifier design.<a class="footnote-ref" id="fnref:21" href="#fn:21">21</a>

<h2 id="see-also">See also</h2>
<ul><li><a href="/facts/FET_amplifier/537sxPg2">FET amplifier</a></li>
<li><a href="/facts/Power_electronics/8BAQ3jDP">Power electronics</a></li></ul>

<h2 id="external-links">External links</h2>

Wikimedia Commons has media related to RF power amplifiers.

<ul><li>Fuentes, Carlos (October 2008). <a href="http://cas.web.cern.ch/cas/Denmark-2010/Caspers/AN-GT101A-Microwave%20Power%20Amplifier%20Fundamentals%2008-10-27%20%20CAS2010.pdf">Microwave Power Amplifier Fundamentals</a> (PDF) (Report). Bern, Switzerland: <a href="/facts/European_Centre_for_Nuclear_Research/y1gwRchm">European Centre for Nuclear Research</a>. Retrieved 5 March 2013.</li></ul>
<ul><li>Khanifar, Ahmad (1 December 2014). <a href="http://www.linamptech.com/technical-support/rf-power-amplifier-design-for-digital-predistortion">"Wideband RF Power Amplifier Design Guidelines / RF Power Amplifier Design for Digital Predistortion"</a>. linamptech.com. Technical support. Laguna Hills, CA: Linamp Technologies, Inc. Retrieved 1 December 2014.</li></ul>

<h2 id="references">References</h2>

<ol>
<li id="fn:1">"RF Amplifiers". info.apitech.com. Retrieved 18 May 2021. <a href="https://info.apitech.com/rf-amplifiers-va" target="_blank">https://info.apitech.com/rf-amplifiers-va</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></li>
<li id="fn:2">Lee, Thomas (2003). The Design of CMOS Radio-Frequency Integrated Circuits. Cambridge, UK: Cambridge University Press. pp. 494–503. <a href="#fnref:2" class="footnote-back-ref">↩</a></li>
<li id="fn:3">Cloutier, Stephen R. (WA1QIX). "Class E, AM transmitter descriptions, circuits, etc". www.classeradio.com. WA1QIX. Retrieved 6 June 2015 – via qrz.com.{{cite web}}: CS1 maint: numeric names: authors list (link) <a href="http://www.qrz.com/db/WA1QIX" target="_blank">http://www.qrz.com/db/WA1QIX</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></li>
<li id="fn:4">Lee, Thomas (2003). The Design of CMOS Radio-Frequency Integrated Circuits. Cambridge, UK: Cambridge University Press. pp. 494–503. <a href="#fnref:4" class="footnote-back-ref">↩</a></li>
<li id="fn:5">Baliga, B. Jayant (2005). Silicon RF Power MOSFETs. World Scientific. p. 1. ISBN 9789812561213. <a href="9789812561213" target="_blank">9789812561213</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></li>
<li id="fn:6">"Ameritron ALS-1300: 1200 Watt no-tune TMOS-FET amplifier". product information downloads. MFJ Enterprises. Archived from the original on 23 April 2014. Retrieved 6 June 2015. <a href="https://web.archive.org/web/20140423115819/http://www.ameritron.com/Downloads/index.php?productid=ALS-1300&filename=ALS-1300.pdf&company=ameritron" target="_blank">https://web.archive.org/web/20140423115819/http://www.ameritron.com/Downloads/index.php?productid=ALS-1300&filename=ALS-1300.pdf&company=ameritron</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></li>
<li id="fn:7">Perugupalli, Prasanth; Leighton, Larry; Johansson, Jan; Chen, Qiang (2001). "LDMOS RF power transistors and their applications" (PDF). In Dye, Norman; Granberg, Helge (eds.). Radio Frequency Transistors: Principles and practical applications. Elsevier. pp. 259–92. ISBN 9780080497945. <a href="9780080497945" target="_blank">9780080497945</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></li>
<li id="fn:8">Austin, W. M.; Dean, J. A.; Griswold, D. M.; Hart, O. P. (November 1966). "TV Applications of MOS Transistors". IEEE Transactions on Broadcast and Television Receivers. 12 (4): 68–76. doi:10.1109/TBTR1.1966.4320029. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></li>
<li id="fn:9">Baliga, B. Jayant (2005). Silicon RF Power MOSFETs. World Scientific. p. 1. ISBN 9789812561213. <a href="9789812561213" target="_blank">9789812561213</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></li>
<li id="fn:10">Perugupalli, Prasanth; Leighton, Larry; Johansson, Jan; Chen, Qiang (2001). "LDMOS RF power transistors and their applications" (PDF). In Dye, Norman; Granberg, Helge (eds.). Radio Frequency Transistors: Principles and practical applications. Elsevier. pp. 259–92. ISBN 9780080497945. <a href="9780080497945" target="_blank">9780080497945</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></li>
<li id="fn:11">Perugupalli, Prasanth; Leighton, Larry; Johansson, Jan; Chen, Qiang (2001). "LDMOS RF power transistors and their applications" (PDF). In Dye, Norman; Granberg, Helge (eds.). Radio Frequency Transistors: Principles and practical applications. Elsevier. pp. 259–92. ISBN 9780080497945. <a href="9780080497945" target="_blank">9780080497945</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></li>
<li id="fn:12">UTE I. VON MEHLEM, ROBERT E. WALLIS (1989). "SOLID-STATE POWER AMPLIFIERS FOR SATELLITE RADAR ALTIMETERS" (PDF). Johns Hopkins University. <a href="https://secwww.jhuapl.edu/techdigest/Content/techdigest/pdf/V10-N04/10-04-Mehlem.pdf" target="_blank">https://secwww.jhuapl.edu/techdigest/Content/techdigest/pdf/V10-N04/10-04-Mehlem.pdf</a> <a href="#fnref:12" class="footnote-back-ref">↩</a></li>
<li id="fn:13">W.Q. Lohmeyer, K. Cahoy (2013). "Space weather radiation effects on geostationary satellite solid-state power amplifiers". Space Weather. 11 (8): 476–488. Bibcode:2013SpWea..11..476L. doi:10.1002/swe.20071. <a href="https://agupubs.onlinelibrary.wiley.com/doi/10.1002/swe.20071" target="_blank">https://agupubs.onlinelibrary.wiley.com/doi/10.1002/swe.20071</a> <a href="#fnref:13" class="footnote-back-ref">↩</a></li>
<li id="fn:14">Baliga, B. Jayant (2005). Silicon RF Power MOSFETs. World Scientific. p. 1. ISBN 9789812561213. <a href="9789812561213" target="_blank">9789812561213</a> <a href="#fnref:14" class="footnote-back-ref">↩</a></li>
<li id="fn:15">Asif, Saad (2018). 5G Mobile Communications: Concepts and Technologies. CRC Press. p. 134. ISBN 9780429881343. <a href="9780429881343" target="_blank">9780429881343</a> <a href="#fnref:15" class="footnote-back-ref">↩</a></li>
<li id="fn:16">Perugupalli, Prasanth; Leighton, Larry; Johansson, Jan; Chen, Qiang (2001). "LDMOS RF power transistors and their applications" (PDF). In Dye, Norman; Granberg, Helge (eds.). Radio Frequency Transistors: Principles and practical applications. Elsevier. pp. 259–92. ISBN 9780080497945. <a href="9780080497945" target="_blank">9780080497945</a> <a href="#fnref:16" class="footnote-back-ref">↩</a></li>
<li id="fn:17">Baliga, B. Jayant (2005). Silicon RF Power MOSFETs. World Scientific. p. 1. ISBN 9789812561213. <a href="9789812561213" target="_blank">9789812561213</a> <a href="#fnref:17" class="footnote-back-ref">↩</a></li>
<li id="fn:18">Perugupalli, Prasanth; Leighton, Larry; Johansson, Jan; Chen, Qiang (2001). "LDMOS RF power transistors and their applications" (PDF). In Dye, Norman; Granberg, Helge (eds.). Radio Frequency Transistors: Principles and practical applications. Elsevier. pp. 259–92. ISBN 9780080497945. <a href="9780080497945" target="_blank">9780080497945</a> <a href="#fnref:18" class="footnote-back-ref">↩</a></li>
<li id="fn:19">Asif, Saad (2018). 5G Mobile Communications: Concepts and Technologies. CRC Press. p. 134. ISBN 9780429881343. <a href="9780429881343" target="_blank">9780429881343</a> <a href="#fnref:19" class="footnote-back-ref">↩</a></li>
<li id="fn:20">"A 600W broadband HF/6m amplifier using affordable LDMOS devices". 27 October 2019. <a href="https://qrpblog.com/2019/10/a-600w-broadband-hf-amplifier-using-affordable-ldmos-devices/" target="_blank">https://qrpblog.com/2019/10/a-600w-broadband-hf-amplifier-using-affordable-ldmos-devices/</a> <a href="#fnref:20" class="footnote-back-ref">↩</a></li>
<li id="fn:21">Ozalas, Matthew (14 January 2015). How to design an RF power amplifier – the basics (short how-to video). Retrieved 10 February 2015 – via youtube.com. <a href="https://www.youtube.com/watch?v=WAingaHfBMs" target="_blank">https://www.youtube.com/watch?v=WAingaHfBMs</a> <a href="#fnref:21" class="footnote-back-ref">↩</a></li>
</ol>

RF power amplifier open-in-new

RF power amplifier