AD8186ARUZ-RL Analog Devices Inc, AD8186ARUZ-RL Datasheet - Page 15
Manufacturer Part Number
Analog Devices Inc
Specifications of AD8186ARUZ-RL
3 x 2:1
Voltage Supply Source
Voltage - Supply, Single/dual (±)
3.5 V ~ 5.5 V
Current - Supply
-40°C ~ 85°C
Package / Case
24-TSSOP (0.173", 4.40mm Width)
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
The AD8186/AD8187 are targeted mainly for use in single-
supply 5 V systems. For operating on these supplies, both V
be referenced to ground. Normally, the DV
set to the same positive supply as the driving logic.
For dc-coupled single-supply operation, it is necessary to set an
appropriate input dc level that is within the specified range of the
amplifier. For the unity-gain AD8186, the output dc level will
be the same as the input, while for the gain-of-two AD8187, the
Figure 10 shows a circuit that provides a gain-of-two and is
dc-coupled. The video input signals must have a dc bias
from their source of approximately 1.5 V. This same volt-
age is applied to V
the video signal is at 1.5 V, the output will also be at the
same voltage. This is close to the lower dynamic range of
both the input and the output.
When the input goes most positive, which is 700 mV above the
black level for a standard video signal, it reaches a value of 2.2 V
and there is enough headroom for the signal. On the output
side, the magnitude of the signal will change by 1.4 V, which
will make the maximum output voltage 2.2 V + 1.4 V = 3.6 V.
This is just within the dynamic range of the output of the part.
When a video signal is ac-coupled, the amount of dynamic range
required to handle the signal can potentially be double that
required for dc-coupled operation. For the unity-gain AD8186,
input can be biased to obtain an appropriate output dc level.
should be tied to ground. The control logic pins will
of the AD8187. The result is that when
TYPICAL INPUT LEVELS
(ALL 6 OUTPUTS)
Figure 10. DC-Coupled (Bypassing and Logic Not Shown)
supply should be
3V TO 5V
there is still enough dynamic range to handle an ac-coupled,
standard video signal with 700 mV p-p amplitude.
If the input is biased at 2.5 V dc, the input signal can potentially go
700 mV both above and below this point. The resulting 1.8 V and
2.2 V are within the input signal range for single 5 V operation.
Since the part is unity-gain, the outputs will follow the inputs,
and there will be adequate range at the output as well.
When using the gain-of-two AD8187 in a simple ac-coupled
application, there will be a dynamic range limitation at the output
caused by its higher gain. At the output, the gain-of-two will
produce a signal swing of 1.4 V, but the ac coupling will double
this required amount to 2.8 V. The AD8187 outputs can only
swing from 1.4 V to 3.6 V on a 5 V supply, so there are only
2.2 V of dynamic signal swing available at the output.
A standard means for reducing the dynamic range requirements
of an ac-coupled video signal is to use a dc restore. This circuit
works to limit the dynamic range requirements by clamping the
black level of the video signal to a fixed level at the input to the
amplifier. This prevents the video content of the signal from
varying the black level as happens in a simple ac-coupled circuit.
After ac coupling a video signal, it is always necessary to use a
dc restore to establish where the black level is. Usually, this
appears at the end of a video signal chain. This dc restore circuit
needs to have the required accuracy for the system. It compen-
sates for all the offsets of the preceding stages. Therefore, if a
dc restore circuit is to be used only for dynamic-range limiting,
it does not require great dc accuracy.
TYPICAL OUTPUT LEVELS
(ALL 3 OUTPUTS)