发明授权
US5939940A Low noise preamplifier for a magnetoresistive data transducer 失效
用于磁阻数据传感器的低噪声前置放大器

Low noise preamplifier for a magnetoresistive data transducer
摘要:
A low noise preamplifier design which is configured such that the current through the first stage load resistor may be made relatively small in value making it possible to achieve a relatively large gain in the first stage thereby reducing the noise contribution of the load resistor and, concurrently, significantly reducing the noise contribution of the second stage as well. This is effectuated by supplying a substantially fixed amount of current to certain nodes in the first stage of the preamplifier through a pair of current sources, the currents being of an amount sufficient to subtract out the bias current that is applied through a series connected variable resistance, such as that of a magnetoresistive ("MR") read head. As a consequence, only a relatively small amount of current is actually fed through the load resistor, and its value may be increased to provide an increased gain for the first stage. Therefore, the noise contribution of the load resistor and the second stage may be rendered relatively negligible.
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