standard deviation of current difference) is larger than a "mismatch" (stdev) of one device by sqrt(2.0)~1.4 (assuming there is no correlation … •Current ratioing is achieved by only scaling the width of transistors. For M2=1, the "mismatch" between two devices (i.e. The mirror mismatch betweenIC(QNl)andIC(QN2)produces small-signal variations ofIC(QNl) (iC(QNl))andIC(QN2) (iC(QN2))from their nominal values generated when supposing the currents are well matched. •We thus prefer to employ a “unit” transistor and create copies by repeating such a device. •Current mirrors usually employ the same length for all of the transistors. The change in current results in the total variation of the reference voltage(Vrej)which can be represented byvref. How do you define "a current mismatch between mirrors"? 3.2.2 Mo deling of CMOS transistor mismatc h Mismatc h in device parameters can b e mo deled b y using di eren ttec hniques. mismatch is the pr o c ess that c auses time-indep endent r andom variations in physic al quantities of identic al ly designe d devic es.
Are you interested in a variance (or standard deviation) of the difference of two currents in a current mirror, or of the current ratio? A current mirror is a circuit block which functions to produce a copy of the current flowing into or out of an input terminal by replicating the current in an output terminal. An important feature of the current mirror is a relatively high output resistance which helps to keep the output current … Thus, a bandgap reference with high immunity to current-mirror mismatch is desired. current-mirror mismatch has been discussed and defined as the leading one. •Direct scaling of the width also faces difficulties. For M1, we can write: P BWAcc Power Speed Accuracy PE rel. Mismatch on the design of elementary stages- Current Mirror (II) We define the performance equation (PE): To calculate the errors in Ios (Accrel), we first go through the errors in the currents of M1 and M2 (current mirror transistors, in and out, respectively).
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