Adjust or remove the feedback and gain components
to provide reduced or additional gain and filtering. When using a feedback
capacitor, be aware that an integrator amplifier circuit can be created
unintentionally. The following measurements use no external capacitors (See the
OPA607 low gain stabilization, documented in the Decompensated
Amplifier Stabilization Circuit design to use the OPA607 for
< 5 V/V gain).
Figure 3-1 shows the red test point supplies VS+ and the yellow test point
supplies VS- to all four amplifiers. The black test point is
connected to chassis ground, and is shorted to the yellow test point
VS- by a ferrite bead L2. L2 can be opened to enable a bipolar
supply for use with ground-referenced test equipment.
The total supply should be no higher than 5 V to avoid damaging the amplifiers. To avoid damage
to a typical target ADC, this test uses 3.3 VS. The default amplifier
output reference is mid-supply; for zero current, the amplifier has an output of
1.65 V.
Set the oscilloscope input to high-impedance mode and attach the BNC output (labeled J2) to the oscilloscope. Alternatively, the test point Vo can be used with a hook-probe lead.
Attach the function generator to the J3 BNC input.
Set both the input slide switch and the output slide switch to the same incremental position to enable the corresponding amplifier. When both switches are in position 1, the OPA365-Q1 is enabled.
Power-on the system and use the oscilloscope to compare the rise times, noise, THD, and overdrive recovery time of the four different amplifier devices and or circuit configurations.