| 摘要 |
PROBLEM TO BE SOLVED: To improve an NF while suppressing noise near DC of a cascode-connection low-noise amplifier. SOLUTION: An LNA 30 is provided with a first amplifier part 1, a second amplifier part 2, a current detection part 3, a capacitor C1, and a resistor R1. The parallel-connected capacitor C1 and resistor R1 are provided between the second amplifier part 2 and the first amplifier part 1. The second amplifier part 2 and the first amplifier part 1 are cascaded with each other via the parallel-connected capacitor C1 and resistor R1. The current detection part 3 is composed so that the plus-side input is connected to one end of the capacitor C1 and resistor R1 and the minus-side input is connected to the other end of the capacitor C1 and resistor R1 in order to monitor a bias current flowing in the resistor R1. When the bias current is changed from a prescribed value, the current detection part controls a current value at a lower frequency and that at DC to make them constant while outputting a signal (a feedback current or a feedback voltage) for correcting the bias current to the first amplifier part. COPYRIGHT: (C)2008,JPO&INPIT
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