LOW_NOISE_5_V_SUPPLY

Published:2009/6/23 4:23:00 Author:Jessie | From:SeekIC

Standard three-terrrtinal regulator ICs can be noisy. The key is the noise over the 10-Hz to 10-kHz band; measurements revealed a 40-dB improvement over standard three-terminal regulators.The regulator is built around a 5-V buried-Zener reference. It's the buried Zener's inherently low noise that makes the finished supply so quiet. Measured over a 10-Hz to 10-kHz band, the 5-V out-put contains just 7 μV rms of noise at full load. The 10-Hz to 10-kHz noise can be further reduced to 2.5 μV rms by adding a 100-p,H, 1000-μF output filter. The noise characteristics of the reference are tested and guaranteed to a maximum of 11 μV over the band of interest.An extemal boost transistor, the ZBD949, provides gain to meet a 200-mA output current requirement. Current limiting is achieved by ballasting the pass transistor and clamping the base drive.Although the oscillator only requires 200 mA, it's possible to extend the output current to at least 1 A.



Reprinted Url Of This Article:
http://www.seekic.com/circuit_diagram/Power_Supply_Circuit/LOW_NOISE_5_V_SUPPLY.html

Print this Page | Comments | Reading(3)