are buffered by a pair of unity gain amplifiers and passed to the comp box microcontroller ADC conversion inputs. The
converted sense signals are transmitted to the oscilloscope when requested by an Auto Offset cycle, where they are
processed by the oscilloscope according to the selected Auto Offset mode. The processed mean value or individual A and B
offset values are sent back to the probe microcontroller, which drives the tip offset DAC signals accordingly.
Operating voltage window
Voltage window
The operating voltage window defines the input signal voltage range within which probe measurements can be made with
good fidelity. The operating voltage window limits is a function of input dynamic range, offset and, in the case of the
P77C292MM adapter, V
term
. In the figures below, the grey area demonstrates the range of signals that can be measured by
a tip. The smaller green box illustrates the dynamic range considering specific offset levels. The dynamic range square can
be moved around within the operating window by adjusting the A and B offset settings.
Figure 10: Operating voltage window (TekFlex solder-in tips)
The A operating voltage window range of ±5.25 V is shown on the vertical axis and the B operating voltage window range of
±5.25 V is shown on the horizontal axis. The dynamic range is also shown on the figure as the smaller green square. The
TekFlex solder tip single-ended dynamic range for both the A and B inputs is 2.5 V
p-p
. Differentially, the solder tip dynamic
range is 5 V
p-p
.
Because there are several step gain values available within the TDP7700 Series Probe Amplifier, the actual size of the
dynamic range square depends upon the oscilloscope vertical scale factor setting. The vertical scale factor determines the
required probe amplifier step gain setting, which is automatically set to the proper value under the oscilloscope control.
The dynamic range square is set to its full-size 2.5 V
p-p
setting when the vertical scale factor is set to large enough V/div
settings that a 2.5 V
p-p
signal can be fully displayed on the oscilloscope. As the vertical scale factor is set to lower V/div
settings, the probe amplifier step gain threshold will eventually be reached and the step gain value will be increased by one
step. In C and D mode, only common-mode and differential offset adjustments are possible. For active tips, this is
represented by the one-dimensional figures below.
Figure 11: Operating voltage window (diferential mode, flex tip)
Theory of operation
TDP7700 Series TriMode™ Probes Technical Reference
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