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Bridge circuit
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<h2 id="bridge-current-equation">Bridge current equation</h2> <p>From the figure to the right, the bridge current is represented as <i>I</i>5 </p><p>Per <a href="/facts/Th%C3%A9venin%27s_theorem/rwYa905x">Thévenin's theorem</a>, finding the Thévenin equivalent circuit which is connected to the bridge load <i>R</i>5 and using the arbitrary current flow <i>I</i>5, we have: </p><p>Thevenin Source (<i>V</i>th) is given by the formula: </p><p> V t h = ( R 2 R 1 + R 2 − R 4 R 3 + R 4 ) × U {\displaystyle V_{th}=\left({\frac {R_{2}}{R_{1}+R_{2}}}-{\frac {R_{4}}{R_{3}+R_{4}}}\right)\times U} </p><p>and the Thevenin resistance (<i>R</i>th): </p><p> R t h = ( R 1 + R 3 ) × ( R 2 + R 4 ) R 1 + R 3 + R 2 + R 4 {\displaystyle R_{th}={\frac {(R_{1}+R_{3})\times (R_{2}+R_{4})}{R_{1}+R_{3}+R_{2}+R_{4}}}} </p><p>Therefore, the current flow (<i>I</i>5) through the bridge is given by <a href="/facts/Ohm%27s_law/PjfEyTgI">Ohm's law</a>: </p><p> I 5 = V t h R t h + R 5 {\displaystyle I_{5}={\frac {V_{th}}{R_{th}+R_{5}}}} </p><p>and the voltage (<i>V</i>5) across the load (<i>R</i>5) is given by the <a href="/facts/Voltage_divider/PYYlGlYU">voltage divider</a> formula: </p><p> V 5 = R 5 R t h + R 5 × V t h {\displaystyle V_{5}={\frac {R_{5}}{R_{th}+R_{5}}}\times V_{th}} </p> <h2 id="see-also">See also</h2> <ul><li><a href="/facts/Phantom_circuit/MI3KPDcf">Phantom circuit</a> - a use of balanced bridge circuits in telephony</li> <li><a href="/facts/Lattice_filter/3lP9UhL1">Lattice filter</a> - an application of bridge topology to all-pass filters</li></ul> <h2 id="gallery">Gallery</h2> <h2 id="external-links">External links</h2> <ul><li><a href="/facts/Jim_Williams_(analog_designer)/h27m64Pp">Jim Williams</a>, <a href="http://cds.linear.com/docs/en/application-note/an43f.pdf">"Bridge circuits: Marrying gain and balance"</a>, Linear Technology Application Note 43, June 1990.</li> <li><a href="http://www.allaboutcircuits.com/vol_1/chpt_8/10.html">Bridge circuits</a> - Chapter 8 from an online book.</li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>Bureau of Naval Personnel, Basic Electricity, p.114, Courier Dover Publications, 1970 ISBN 0-486-20973-3. <a href="/wiki/ISBN_(identifier)" target="_blank">/wiki/ISBN_(identifier)</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>Clarence W. De Silva, Vibration monitoring, testing, and instrumentation, pp.2.43-2.49, CRC Press, 2007 ISBN 1-4200-5319-1 <a href="/wiki/ISBN_(identifier)" target="_blank">/wiki/ISBN_(identifier)</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>All about circuits: AC bridge circuits <a href="http://www.allaboutcircuits.com/vol_2/chpt_12/5.html" target="_blank">http://www.allaboutcircuits.com/vol_2/chpt_12/5.html</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> </ol>