Large-Bandwidth High-Gain Low-Noise Transimpedance Amplifier for Scanning Tunneling Microscope

In this work, a design of large-bandwidth high-gain low-noise transimpedance amplifier (TIA) for scanning tunneling microscope (STM) is proposed. The simulations show that the proposed TIA has the bandwidth higher than 200 kHz, two orders of magnitude higher than those of conventional commercial TIAs for STM. At low frequencies, the noises of the proposed TIA are almost the same as the conventional commercial ones with the same transimpedance gain. At high frequencies, its calculated input equivalent noise voltage power spectral density (PSD) is 40 nV²/Hz and its input equivalent noise current PSD is 3.2 fA²/Hz at 10 kHz. The corresponding values are 23 nV²/Hz and 88 fA²/Hz at 100 kHz. The STM with the proposed TIA can meet the needs of fast high-quaility STM imaging measurements and fast high-energy-resolution scanning tunneling spectra measurements for the low-conducting materials, such as complex organic systems and wide bandgap semiconductors.