Norton_low_noise_amplifier

Published:2009/7/25 2:00:00 Author:Jessie | From:SeekIC

The programmability of a Norton and the ability to shut off thenoninverting input current mirror can be used to Improve nolse characteristics. For an inverting application, where the noninverting input would only be used for bias, an alternate biasing scheme (the nVBE biasing) can be used as shown in Fig. 11-20A. This allows shutting off the input current mirror, which, in itself, reduces input noise by a factor of two. Also, the input-stage programming current can be increased to further reduce the noise voltage at the expense of an increase in input noise current and low-frequency 1/f noise (which is generally not a problem in low-input-impedance wideband amplifiers). The typical effect on noise versus input-stage current is shown in Figs. 11-20B and 11-20C.



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