LOW NOISE AMPLIFIER, AND ULTRASONIC PROBE AND DIAGNOSTIC DEVICE USING SAME

摘要

The LNA has a sampling switch as a load. A method to reduce the ON-resistance of the sampling switch is to connect a source follower circuit to the output stage to lower the common voltage of output signals while lowering the output impedance, but this method leads to a problem regarding increase in power consumption. In order to solve this problem, a common node of a differential transistor pair constituting a differential amplifier at the first stage of the LNA is connected to a node shared by drain terminals of transistors constituting a differential source follower at the second stage. Thus, the source follower current at the second stage is reused by the differential amplifier at the first stage.