Low noise preamplifier suitable for high impedance sources

The amplification of low signals from inductive transducers is not an easy task. Existing integrated amplifiers are good enough but in some applications the requirements are for better signal to noise ratio and high gain. For example the LT1028/LT1128's voltage noise is less than the noise of a 50Ω resistor. Here we are discussing the practical aspects for designing an ultra low noise preamplifier with input voltage noise less than 5Ω resistor, which is about 0.3nV/√Hz.