Datasheet

Video Cable Driver Using ±5 Volt Supplies
The AD844 can be used to drive low impedance cables. Using
±5 V supplies, a 100 Ω load can be driven to ±2.5 V with low
distortion. Figure 35a shows an illustrative application which
provides a noninverting gain of 2, allowing the cable to be
reverse-terminated while delivering an overall gain of +1 to the
Figure 35a. The AD844 as a Cable Driver
Figure 35c. Differential Phase for the Circuit of Figure 35a
load. The –3 dB bandwidth of this circuit is typically 30 MHz.
Figure 35b shows a differential gain and phase test setup. In
video applications, differential-phase and differential-gain
characteristics are often important. Figure 35c shows the varia-
tion in phase as the load voltage varies. Figure 35d shows the
gain variation.
Figure 35b. Differential Gain/Phase Test Setup
Figure 35d. Differential Gain for the Circuit of Figure 35a
Applications–AD844
REV. C
–11–
High Speed DAC Buffer
The AD844 performs very well in applications requiring
current-to-voltage conversion. Figure 36 shows connections for
use with the AD568 current output DAC. In this application
the bipolar offset is used so that the full-scale current is
±5.12 mA, which generates an output of ±5.12 V using the
1 kΩ application resistor on the AD568. Figure 37 shows the
full-scale transient response. Care is needed in power supply
Figure 36. High Speed DAC Amplifier
decoupling and grounding techniques to achieve the full 12-bit
accuracy and realize the fast settling capabilities of the system.
The unmarked capacitors in this figure are 0.1 µF ceramic (for
example, AVX Type SR305C104KAA), and the ferrite induc-
tors should be about 2.5 µH (for example, Fair-Rite Type
2743002122). The AD568 data sheet should be consulted for
more complete details about its use.
Figure 37. DAC Amplifier Full-Scale Transient Response