On the Optimum Source Impedance for MRI Phased Array Coils

Paul Joseph Cassidy¹

Analytical expressions are presented for MRI phased array preamplifiers in terms of blocking impedance, S21 decoupling, minimum noise factor and gain based on CMOS common-source inductively degenerated low noise amplifiers. These expressions support the idea of using a source impedance greater than 50 Ohms for enhanced decoupling and minimum noise factor at the expense of gain.