Ultra low-noise preamplifier for low-frequency noise measurementsin electron devices

The design and realization of an ultra-low-noise, high-input-impedance amplifier for low-frequency noise measurements in electronic devices is presented. Special care is devoted to the solution of typical problems encountered in the design of low-noise low-frequency equipment, such as power supply noise and temperature fluctuations. The ultra-low-noise preamplifier has a bandwidth of over seven decades with a low-frequency roll-off of 4 mHz. The noise characteristics obtained are sensibly better than those of commercial preamplifiers commonly adopted in low-frequency noise measurements. The application of this preamplifier to the realization of standard 1/f^γ noise generators is presented