BJT%20current%20mirror%20review_web

BJT%20current%20mirror%20review_web - Concept of Current...

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ECE 304 Spring 2008 by Brian Ma 1 Concept of Current Mirror ¾ The motivation behind a current mirror is to sense the current from a “golden current source” and duplicate this “golden current” to other locations.
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ECE 304 Spring 2008 by Brian Ma 2 Bipolar Current Mirror Circuitry ¾ The diode-connected Q REF produces an output voltage V 1 that forces I copy1 = I REF , if Q 1 = Q REF .
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ECE 304 Spring 2008 by Brian Ma 3 Multiple Copies of I REF ¾ Multiple copies of I REF can be generated at different locations by simply applying the idea of current mirror to more transistors.
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ECE 304 Spring 2008 by Brian Ma 4 Current Scaling ¾ By scaling the emitter area of Q j n times with respect to Q REF , I copy,j is also n times larger than I REF . This is equivalent to placing n unit-size transistors in parallel.
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ECE 304 Spring 2008 by Brian Ma 5 Example: Scaled Current
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ECE 304 Spring 2008 by Brian Ma 6 Fractional Scaling ¾ A fraction of I REF can be created on Q 1 by scaling up the emitter area of Q REF .
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ECE 304 Spring 2008 by Brian Ma
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BJT%20current%20mirror%20review_web - Concept of Current...

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