Overdrive Recovery
Overdrive occurs when any
channel is driven out of its
range of
divisions.
The 1
has extraordinarily
overdrive recovery, and this feature may
to greatly extend measurement resolution. For example, suppose a signal
the
stabilized immediately at
V or if perhaps had some small
aberration
the
By setting the
offset to
V and
the sensitivity to 1
aberrations of just 0.1% of the original
transition will
divisions in amplitude (0.1% of 25 V is 25
or
divisions at 1
Any amplifier
ultimately reach an equilibrium value after an input step
(although its accuracy
determine how far that equilibrium value is from
the correct value). The
ability to
quickly to within a very small
fraction of its equilibrium value is
The &me it takes the llA34 to
settle to within a stated fraction of the equilibrium value
its overdrive
recovery time.
the overdrive recovery time of an 1
takes
care and can
lead to
surprising results. An interesting experiment is to use a very flat
as the Tektronix
to pulse the
Connect the
generator’s fast-rise output to the
input through a short (one foot or less)
cable and select
impedance. Adjust the puke amplitude to
volt Set the
sensitivity to 1
Each division now represents
0.1% of the input signal. Trigger the
and observe
recovery of
the
using
sweep rate. Now increase the cable length by
about three feet (for example,
a
of
cable, Tektronix
part 012005701) and observe the new
Figure 3-2.
The waveform
due to skin effect loss in the longer cable. What is
surprising is that the
effect loss persists for over
even though the
cable delay is only 5
At
the loss is
0.02%.
This experiment shows the importance of using a short cable to test overdrive
A second surprise is that skin effect loss
almost completely (after
two cable delays) when one end is
To
this,
the short cable again, and select 1
input impedance on
the
Insert a 2X attenuator
the
and the pulse generator to
improve the reverse termination and to provide
amplitude signal
before. Observe the response and change cables again Even at 0.1% per
division the skin effect loss is hard to detect without the forward termination.
Reference Supplement