An Integrated Negative Resistance Current Amplifier to Enhance the Sensitivity of a Weakly Coupled Local Detector
Chunqi Qian 1 , Qi Duan 1 , Stephen Dodd 1 , Alan Koretsky 1 , and Joseph Murphy-Boesch 1
NIH, Bethesda, MD, United States
A localized detection coil with an integrated negative
resistance amplifier has been constructed to enhance the
local sensitivity of inductively coupled receive coils.
When the transistor is grounded on its drain, the
feedback effect transforms capacitive impedance on the
source into negative resistance on the gate, thus
increasing the signal current in the LC resonator.
Although the integrated amplifier consumes only 86 μW of
power, 14 dB gain is achievable with excellent noise
performance. Such a detection scheme enables high
resolution animal imaging at 3T with small active coils
inductively coupled to larger clinical coils using the
standard signal interface.
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