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Current mirrors and compliance of output

leeb_965

Feb 5, 2012
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Feb 5, 2012
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Hi,

Can someone tell me the equation to find the compliance of output please? Im missing one of my lecture notes. Its for a simple current mirror configuration.

Also can someone confirm that for Output current with early effect is:

Iout = (Iin / 1 + 2/B) x (Vout - VBE / VA)

Thanks in advance
 

Harald Kapp

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Nov 17, 2011
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Your equation cannot be correct:

1) you need to set parentheses to group terms in nominator and denominator of the fractions. As you write it common rules of evaluating equations apply (operator precedence). For example (Vout - VBE / VA) implies that you first evaluate VBE/VA and then subtract this from Vout. Which is impossible since VBE/VA has no dimension (units cancel), but Vout has a dimension (unit Volts).

2) Even assuming the parentheses were set as needed, the result of the right side of the equation is without dimension, but Iout needs a dimension (unit Amperes).

Both your questions are answered in detail here. http://users.ece.gatech.edu/mleach/ece3050/notes/bjt/bjtmirr.pdf
with explanations how to arrive at the results.

Harald
 

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