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THS4520
SLOS503B – SEPTEMBER 2006 – REVISED JULY 2007
particular interest because their joint interaction represent measurements of a THS4520 evaluation
reflects the usable slewing and bandwidth limits of a board in the default unity-gain configuration with R
L
=
device. Output swing and frequency limits are often 200 Ω . For more information on the circuit
prime consideration when picking a device and configuration, see the information on the THS4520
quantifying their joint impact on HD allows a more evaluation board later in this section.
precise judgment on the ability of a device to meet
The first two plots (Figure 67 andFigure 68 ) are for
the need for speed. The curves that separate each
HD2 and HD3 respectively, with a power supply of
colored region represent the value of HD2,3
± 2.5 V. The line labeled Large Signal BW in each of
indicated on the plot. Following a curve over the
the two plots represents the measured large signal
ranges of output swing and frequency show the
bandwidth over the range of output signal swing in
conditions over which that value of HD2,3 occurs.
the plot (V
out
= 1 V
pp
to 8 V
pp
). The BW lines fall in
Note that the horizontal axis represents the base-10 the shaded region that represents very poor
logarithm of frequency in units of MHz. So on the distortion performance: HD2 > –45dBc or HD3 >
horizontal axis the value of ‘2’ represents 100 MHz, –40dBc. The intent in plotting the bandwidth was to
‘1’ represents 10 MHz and ‘0’ represents 1 MHz, provide a realistic comparison between the reported
respectively. This strategy was chosen to provide large signal bandwidth and useful distortion
spacing between curves that allowed the viewer to performance. The areas between the plots are
easily resolve the individual curves. Plotting shaded to help illustrate the 10dB changes in HD2 or
frequency on a linear scale caused the curves to be HD3 between the adjacent curves. The third and
crowded and difficult to distinguish. Unfortunately a fourth plots (Figure 69 andFigure 70 ) are the constant
semilog axis format was not possible because of the contours of HD2 and HD3 respectively for a power
plotting function. The measured data in the plots supply of ± 1.65 V.
Figure 67. Constant HD2 Contours vs Output Swing and log
10
(Frequency - MHz)
V
s
= 2.5 V, Gain = 1, R
L
= 200 Ω
25
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