<p>An issue with the previous circuit is that Q1 will not be saturated unless its base is biased about 0.5 volts above Vcc.</p><p>These circuits operate more efficiently from a single (Vcc) supply. In both circuits, R1 allows Q1 to turn on and pass voltage and current to the load. When the current through R_sense exceeds the design limit, Q2 begins to turn on, which in turn begins to turn off Q1, thus limiting the load current. The optional component R2 protects Q2 in the event of a short-circuited load. When Vcc is at least a few volts, a <a href="https://en.wikipedia.org/wiki/MOSFET" target="_top" class="ke-link">MOSFET</a> can be used for Q1 for lower dropout voltage. Due to its simplicity, this circuit is sometimes used as a <a href="https://en.wikipedia.org/wiki/Current_source" target="_top" class="ke-link">current source</a> for high-power LEDs.<a href="https://en.wikipedia.org/wiki/Current_limiting#cite_note-3" target="_top" class="ke-link">[3]</a></p><div class="figure-open" contenteditable="false" data-ke-type="opengraph" data-ke-align="alignCenter" data-og-type="website" data-og-title="Current limiting - Wikipedia" data-og-description="Current limiting is the practice of imposing a limit on the current that may be delivered to a load to protect the circuit generating or transmitting the current from harmful effects due to a short-circuit or overload. The term "current limiting" is also u" data-og-host="en.wikipedia.org" data-og-source-url="https://en.wikipedia.org/wiki/Current_limiting#cite_note-3" data-og-url="https://en.wikipedia.org/wiki/Current_limiting#cite_note-3" data-og-image="https://scrap.kakaocdn.net/dn/brprPp/hyNPQAqPRY/SKiG6ysPZwpxBrfBUdHkBK/img.png?width=200&height=210&face=0_0_200_210,https://scrap.kakaocdn.net/dn/NwZr2/hyNPSrtAlw/NGebckjw7ePWLj8KHgbYuk/img.png?width=200&height=210&face=0_0_200_210"><a href="https://en.wikipedia.org/wiki/Current_limiting#cite_note-3" target="_blank" data-source-url="https://en.wikipedia.org/wiki/Current_limiting#cite_note-3"><div class="og-image" style="background-image:url(https://scrap.kakaocdn.net/dn/brprPp/hyNPQAqPRY/SKiG6ysPZwpxBrfBUdHkBK/img.png?width=200&height=210&face=0_0_200_210,https://scrap.kakaocdn.net/dn/NwZr2/hyNPSrtAlw/NGebckjw7ePWLj8KHgbYuk/img.png?width=200&height=210&face=0_0_200_210)"></div><div class="og-text"><p class="og-title">Current limiting - Wikipedia</p><p class="og-desc">Current limiting is the practice of imposing a limit on the current that may be delivered to a load to protect the circuit generating or transmitting the current from harmful effects due to a short-circuit or overload. The term "current limiting" is also u</p><p class="og-host">en.wikipedia.org</p></div></a></div><div class="figure-img" data-ke-type="image" data-ke-style="alignCenter" data-ke-mobilestyle="widthOrigin"><img src="https://t1.daumcdn.net/cafeattach/1WUSx/e247a19a8a71bd242d0fad0707c0ae446fcef5e5" class="txc-image" data-img-src="https://t1.daumcdn.net/cafeattach/1WUSx/e247a19a8a71bd242d0fad0707c0ae446fcef5e5" data-origin-width="960" data-origin-height="1280"></div>
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