AD834–Typical Characteristics

REV. C

–4–

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.

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.

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 6. Low Frequency Test Circuit