ADA4177 has a low voltage noise density of 8 nV/√Hz, only twice the Johnson noise of a 1kΩ resistor. Placing a 1KΩ resistor with thermal noise of 4 nV/√Hz at the input of the amplifier increases total input referred noise to 8.9 nV/√Hz. It is important to use low value resistors around a low-noise amplifier.