HA7-2544-2 INTERSIL [Intersil Corporation], HA7-2544-2 Datasheet - Page 6

• Manufacturer Part Number: HA7-2544-2
• Description: 50MHz, Video Operational Amplifier
• Manufacturer: INTERSIL [Intersil Corporation]

Another usage might be required for a direct 50 or 75 load
where the HA-2544 will still swing this 2V signal as shown in
the above display. One important note that must be realized is
that as load resistance decreases the video parameters are
also degraded. For optimal video performance a 1k load is
recommended.
If lower supply voltages are required, such as 5V, many of
the characterization curves indicate where the parameters
vary. As shown the bandwidth, slew rate and supply current
are still very well maintained.
Prototyping and PC Board Layout
When designing with the HA-2544 video op amp as with
any high performance device, care should be taken to use
high frequency layout techniques to avoid unwanted
parasitic effects. Short lead lengths, low source impedance
and lower value feedback resistors help reduce unwanted
poles or zeros. This layout would also include ground plane
construction and power supply decoupling as close to the
supply pins with suggested parallel capacitors of 0.1 F and
0.001 F ceramic to ground.
In the noninverting configuration, the amplifier is sensitive
to stray capacitance (<40pF) to ground at the inverting
input. Therefore, the inverting node connections should be
kept to a minimum. Phase shift will also be introduced as
load parasitic capacitance is increased. A small series
Typical Applications
FIGURE 4. APPLICATION 1, 75 DIFFERENTIAL INPUT BUFFER
SHIELDED
FIGURE 6. APPLICATION 3, 100kHz HIGH PASS 2-POLE
CABLE
INPUT
750pF
BUTTERWORTH FILTER
100
750pF
2.1K
1.21K
1.21K
2.1K
6
f
O
=
2 (2.1K x 750pF)
+
1.21K
-
HA-2544
1
-
+
1.21K
HA-2544
OUTPUT
HA-2544
resistor (20
decouples this effect.
Stability/Phase Margin/Compensation
The HA-2544 has not sacrificed unity gain stability in
achieving its superb AC performance. For this device, the
phase margin exceeds 60 degrees at the unity crossing
point of the open loop frequency response. Large phase
margin is critical in order to reduce the differential phase and
differential gain errors caused by most other op amps.
Because this part is unity gain stable, no compensation pin
is brought out. If compensation is desired to reduce the
noise bandwidth, most standard methods may be used. One
method suggested for an inverting scheme would be a
series R-C from the inverting node to ground which will
reduce bandwidth, but not effect slew rate. If the user wishes
to achieve even higher bandwidth (>50MHz), and can
tolerate some slight gain peaking and lower phase margin,
experimenting with various load capacitance can be done.
Shown in Application 1 is an excellent Differential Input,
Unity Gain Buffer which also will terminate a cable to 75
and reject common mode voltages. Application 2 is a
method of separating a video signal up into the Sync only
signal and the Video and Blanking signal. Application 3
shows the HA-2544 being used as a 100kHz High Pass
2-Pole Butterworth Filter. Also shown is the measured
frequency response curves.
-100
FIGURE 5. APPLICATION 2, COMPOSITE VIDEO SYNC
FIGURE 7. MEASURED FREQUENCY RESPONSE OF
COMPOSITE
-20
-40
-60
-80
0
VIDEO
10
100
SEPARATOR
APPLICATION 3
1K
to 100 ) before the capacitance effectively
1K
FREQUENCY (Hz)
10K
1K
-
+
HA-2544
100K
1K
f
0
= 105.3kHz
1M
1N5711
1N5711
SYNC ONLY
VIDEO AND
BLANK
10M
180
135
90
45
0
-45