Cypher SPM
User Guide
The sample is biased from a voltage source within the Cypher electronics. The feedback resistor R1
sets the amplifier's sensitivity. The output signal representing tip/sample current flow can be mon-
itored by enabling the 'Current' channel in the master channel control panel.
7.5.2 Dual gain
A conceptual diagram of the dual gain ORCA amplifier shows the initial current to voltage converter
stage feeding the input of a second gain stage to create an additional output signal.
In the case of this design the more sensitive signal comes from the second stage and is monitored
as 'Current' from the master channel panel like the single gain ORCA holder.
The output of the current to voltage amplifier's first stage has a lower gain (more total current
range) signal is monitored as 'Current 2' from the master channel panel.
Having a dual gain design is useful in that it expands the dynamic range of your measurement cap-
ability but at a sacrifice of some increased noise at small current levels. In many cases the sample
you may wish to measure may have widely different regions of conductivity where the current may
be too large for the range of the more sensitive stage but suitable for the lower gain stage where
more current can me measured. In this case it is common to see the 'Current' signal (high gain
stage) saturate while the 'Current 2' signal show a measurable current flow.
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7 Standard scanner cantilever holders
