The STM-electronics are based on a digital design. A DSP (digital signal processor) controls the scanning parallel (X, Y) to the surface as well as the tip - sample separation. All scanning/feedback parameters are fully controlled through the STM program. An additional high voltage amplifier and a current preamplifier complement the electronics. There is are options to read data from external devices, too.
The heart of the STM-electronics is a DSP (TSM320C6711) by Texas Instruments. It is integrated into a commercial Single Board Computer (SBC) from Innovative Integration and connects to a Windows® operated PC via USB2.0. The DSP is electronically decoupled from the analog I/O board, which provides 6 D/A outputs (20bit, 50kHz), 4 A/D inputs (18bit, 50kHz) and 32 digital I/O ports. 4 analogue output channels are used to control the piezo-voltages (X, Y, Z) and the sample bias voltage. One input channel records the tunneling current, the others may be used to read other signals (e.g. dI/dV from an external lock-in-amplifier).
The three piezo voltages (X, Y, Z) are amplified by a selectable factor of 1, 3, 10 or 30 to the dual voltage bipolar output. An offset voltage or a modulation voltage may be added to any channel by a potentiometer and via separate inputs. The maximum output voltage is ±200V. An interface to the DSP-board allows reading the gain settings into the STM-program to set the appropriate scaling in the images.
Any I/V-converter with the desired specifications can be used with the STM-program, but it should be externally gain switch able to exploit the manipulation techniques implemented in the software. We supply the Femto DLPCA-200 (gain: 103 … 1011 V/A, bandwidth: 500 … 1.2kHz).
The STM-software is able to read data from the Data Logger Agilent 34970 or the external Lock-In-Amplifier SR830 via the GPIB-interface or RS-232 into the program. Additional data might be read via OLE/COM data exchange with the software.