Ch. 8. Conductive AFM (ORCA) Sec. 8.5. Testing the ORCA Amplifier
3.
Do an I/V plot and confirm the correct
current flow
• Go to AFM Controls-> Do IV panel and
open the I/V voltage controls.
• Press the Do I/V button to perform an
I/V curve.
• Confirm the current flow is the correct
amount based on the test resistor value.
• Confirm the I/V plot is linear with 0
current flow coinciding with 0 volts of
bias voltage.
• If the current is not flowing through 0
then recheck the current and voltage
offsets are set correctly.
Note The 500M Ohm resistor should allow
2nA of current to flow for 1V of bias voltage.
8.5.0.1. Testing the first gain stage of a Dual Gain ORCA Amplifier
Testing the final output of a Dual Gain ORCA amplifier is done in the same manner as testing the the sin-
gle gain ORCA amplifier. Because the two gain stages are in series, the first gain stage is automatically
checked by default.
You can verify that both the Current and Current 2 data channels are active in the software by monitoring
both signals when doing an IV plot. When using the 500M Ohm test resistor, you will notice the limits
of resolution and noise in the Current 2 signal as compared to the Current signal. See
Figure 8.3 on
page 101.
Figure 8.3.: 2nA current flow through a Dual Gain ORCA
The Dual Gain ORCA accessory kit includes a second 1M Ohm test resistor which is more suitable for
the current ranges of the primary gain stage.
DRAFT
Page 101
To Next Page
Loading...