AD834–Typical Characteristics
Figure 1. Mean-Square Output
vs. Frequency
Figure 2. AC Feedthrough
vs. Frequency
Figure 3. Total Harmonic Distortion
vs. Frequency
Figure 1.
Figure 1 is a plot of the mean-square output versus
frequency for the test circuit of Figure 5. Note that the rising
response is due to package resonances.
Figure 2.
For frequencies above 1 MHz, ac feedthrough is
dominated by static nonlinearities in the transfer function and
the finite offset voltages. The offset voltages cause a small frac-
tion of the fundamental to appear at the output, and can be
nulled out.
Figure 3.
THD data represented in Figure 3 is dominated by
the second harmonic, and is generated with 0 dBm input on the
ac input and +1 V on the dc input. For a given amplitude on the
ac input, THD is relatively insensitive to changes in the
dc input amplitude. Varying the ac input amplitude while
maintaining a constant dc input amplitude will affect THD
performance.
By placing capacitors C3/C5 and C4/C6 across load resistors R1
and R2, a simple low-pass filter is formed, and the mean-square
value is extracted. The mean-square response can be measured
using a DVM connected across R1 and R2.
Figure 5. Bandwidth Test Circuit
Figure 4. Test Configuration for Measuring AC
Feedthrough and Total Harmonic Distortion
Figure 5.
The squarer configuration shown in Figure 5 is used
to determine wideband performance because it eliminates the
need for (and the response uncertainties of) a wideband mea-
surement device at the output. The wideband output of a
squarer configuration is a fluctuating current at twice the input
frequency with a mean value proportional to the square of the
input amplitude.
–4–
Figure 6. Low Frequency Test Circuit
REV. C
AD [ ANALOG DEVICES ]
