Data Sheet

AD8031/AD8032

Rev. G | Page 17 of 20

Figure 50 and Figure 51 show the output signal swing and

frequency spectrum at 500 kHz. At this frequency, the output

signal (at VOUT), which has a peak-to-peak swing of 1.95 V

(50 mV to 2 V), has a THD of −68 dB (SFDR = −77 dB).

2V

50mV

10

0%

100

90

0.5V

1µs

Figure 50. Output Signal Swing of Low Distortion Line Driver at 500 kHz

STOP 5MHz

START 0Hz

+9dBm

Figure 51. THD of Low Distortion Line Driver at 500 kHz

Figure 52 and Figure 53 show the output signal swing and

frequency spectrum at 2 MHz. As expected, there is some

degradation in signal quality at the higher frequency. When the

output signal has a peak-to-peak swing of 1.45 V (swinging

from 50 mV to 1.5 V), the THD is −55 dB (SFDR = −60 dB).

This circuit could also be used to drive the analog input of a

single-supply, high speed ADC whose input voltage range is

referenced to ground (for example, 0 V to 2 V or 0 V to 4 V). In

this case, a back termination resistor is not necessary (assuming

a short physical distance from transistor to ADC); therefore, the

emitter of the external transistor would be connected directly to

the ADC input. The available output voltage swing of the circuit

would therefore be doubled.

50mV

10

0%

100

90

1.5V

0.2V

200ns

Figure 52. Output Signal Swing of Low Distortion Line Driver at 2 MHz

+7dBm

START 0Hz

STOP 20MHz

Figure 53. THD of Low Distortion Line Driver at 2 MHz