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PDF HFA1412 Data sheet ( Hoja de datos )
| Número de pieza | HFA1412 | |
| Descripción | Quad/ High Speed/ Low Power/ Video Closed Loop Buffer | |
| Fabricantes | Intersil Corporation | |
| Logotipo |  |
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®
Data Sheet
January 23, 2006
HFA1412
FN4152.4
Quad, 350MHz, Low Power,
Programmable Gain Buffer Amplifier
The HFA1412 is a quad closed loop Buffer featuring user
programmable gain and high speed video performance.
A unique feature of the HFA1412’s pinout allows the user to
select a voltage gain of +1, -1, or +2 (see the “Application
Information” section). The on-chip gain setting resistors
eliminate eight external resistors, thus saving board space or
freeing up space for termination resistors. The on-chip
feedback resistor is preset at the optimum value, and also
eliminates worries about parasitic feedback capacitance.
Additionally, the capacitance sensitive summing node is
buried inside the package where it is unaffected by PCB
parasitics. Compatibility with existing op amp pinouts
provides flexibility to upgrade low gain amplifiers, while
decreasing component count. Unlike most buffers, the
standard pinout provides an upgrade path should a higher
closed loop gain be needed at a future date.
The HFA1412 is an excellent choice for component and
composite video systems as indicated by the excellent gain
flatness, and 0.03%/0.02 Degree Differential Gain/Phase
specifications (RL = 150Ω). Its ability to deliver a gain of +2
withwww.DataSheet4U.com no external resistors makes it particularly desirable for
applications driving double terminated cables.
For Military product, refer to the HFA1412/883 data sheet.
Ordering Information
PART
NUMBER
PART
MARKING
TEMP.
RANGE
(°C)
PKG.
PACKAGE DWG. #
HFA1412IP HFA1412IP -40 to 85 14 Ld PDIP E14.3
HFA1412IPZ HFA1412IPZ -40 to 85 14 Ld PDIP* E14.3
(Note)
(Pb-free)
HFA1412IB HFA1412IB -40 to 85 14 Ld SOIC M14.15
HFA1412IBZ HFA1412IBZ -40 to 85 14 Ld SOIC M14.15
(Note)
(Pb-free)
HA5025EVAL
DIP Evaluation Board For Quad Op
Amp
*Pb-free PDIPs can be used for through hole wave solder
processing only. They are not intended for use in Reflow solder
processing applications.
NOTE: Intersil Pb-free plus anneal products employ special Pb-free
material sets; molding compounds/die attach materials and 100%
matte tin plate termination finish, which are RoHS compliant and
compatible with both SnPb and Pb-free soldering operations. Intersil
Pb-free products are MSL classified at Pb-free peak reflow
temperatures that meet or exceed the Pb-free requirements of
IPC/JEDEC J STD-020.
Features
• User Programmable For Closed-Loop Gains of +1, -1 or
+2 Without Use of External Resistors
• Wide -3dB Bandwidth. . . . . . . . . . . . . . . . . . . . . . 350MHz
• Low Supply Current . . . . . . . . . . . . . . . . . . . . 6mA/Buffer
• Excellent Gain Flatness (to 100MHz). . . . . . . . . . ±0.08dB
• Low Differential Gain and Phase . . . . 0.03%/0.02 Degree
• Very Fast Slew Rate . . . . . . . . . . . . . . . . . . . . . 1650V/µs
• Fast Settling Time (0.1%). . . . . . . . . . . . . . . . . . . . . 28ns
• High Output Current . . . . . . . . . . . . . . . . . . . . . . . . . 55mA
• Excellent Gain Accuracy . . . . . . . . . . . . . . . . . . . 0.99V/V
• Overdrive Recovery . . . . . . . . . . . . . . . . . . . . . . . . <10ns
• Standard Operational Amplifier Pinout
• Pb-Free Plus Anneal Available (RoHS Compliant)
Applications
• Video Distribution Amps
• Flash A/D Drivers
• Video Cable Drivers
• Video Switchers and Routers
• Medical Imaging Systems
• RGB Video Processing
• High Speed Oscilloscopes and Analyzers
Pinout
HFA1412 (PDIP, SOIC)
TOP VIEW
OUT1 1
-IN1 2
+IN1 3
V+ 4
+IN2 5
-IN2 6
OUT2 7
Functional Diagram
14 OUT4
13 -IN4
12 +IN4
11 V-
10 +IN3
9 -IN3
8 OUT3
425 Ω
-IN1 2
+IN1 3
425 Ω
-
+
1 OUT1
425 Ω
-IN2 6
+IN2 5
425 Ω
-
+
7 OUT2
425 Ω
-IN3 9
+IN3 10
425 Ω
-
+
8 OUT3
425 Ω
-IN4 13
+IN4 12
425 Ω
-
+
14 OUT4
1
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 1-888-468-3774 | Intersil (and design) is a registered trademark of Intersil Americas Inc.
Copyright Intersil Americas Inc. 1998, 2005, 2006. All Rights Reserved
All other trademarks mentioned are the property of their respective owners.
1 page  
HFA1412
Application Information
HFA1412 Advantages
The HFA1412 features a novel design which allows the user
to select from three closed loop gains, without any external
components. The result is a more flexible product, fewer part
types in inventory, and more efficient use of board space.
Implementing a quad, gain of 2, cable driver with this IC
eliminates the eight gain setting resistors, which frees up
board space for termination resistors.
Like most newer high performance amplifiers, the HFA1412
is a current feedback amplifier (CFA). CFAs offer high
bandwidth and slew rate at low supply currents, but can be
difficult to use because of their sensitivity to feedback
capacitance and parasitics on the inverting input (summing
node). The HFA1412 eliminates these concerns by bringing
the gain setting resistors on-chip. This yields the optimum
placement and value of the feedback resistor, while
minimizing feedback and summing node parasitics. Because
there is no access to the summing node, the PCB parasitics
do not impact performance at gains of +2 or -1 (see “Unity
Gain Considerations” for discussion of parasitic impact on
unity gain performance).
The HFA1412’s closed loop gain implementation provides
better gain accuracy, lower offset and output impedance,
and better distortion compared with open loop buffers.
Closed Loop Gain Selection
This “buffer” operates in closed loop gains of -1, +1, or +2, with
gain selection accomplished via connections to the ±inputs.
Applying the input signal to +IN and floating -IN selects a gain
of +1 (see next section for layout caveats), while grounding -IN
selects a gain of +2. A gain of -1 is obtained by applying the
input signal to -IN with +IN grounded through a 50Ω resistor.
The table below summarizes these connections:
GAIN
(ACL)
-1
+1
+2
CONNECTIONS
+INPUT
-INPUT
50Ω to GND
Input
Input
NC (Floating)
Input
GND
Unity Gain Considerations
Unity gain selection is accomplished by floating the -Input of
the HFA1412. Anything that tends to short the -Input to GND,
such as stray capacitance at high frequencies, will cause the
amplifier gain to increase toward a gain of +2. The result is
excessive high frequency peaking, and possible instability.
Even the minimal amount of capacitance associated with
attaching the -Input lead to the PCB results in approximately
6dB of gain peaking. At a minimum this requires due care to
ensure the minimum capacitance at the -Input connection.
Table 1 lists five alternate methods for configuring the
HFA1412 as a unity gain buffer, and the corresponding
performance. The implementations vary in complexity and
involve performance trade-offs. The easiest approach to
implement is simply shorting the two input pins together, and
applying the input signal to this common node. The amplifier
bandwidth decreases from 550MHz to 370MHz, but
excellent gain flatness is the benefit. A drawback to this
approach is that the amplifier input noise voltage and input
offset voltage terms see a gain of +2, resulting in higher
noise and output offset voltages. Alternately, a 100pF
capacitor between the inputs shorts them only at high
frequencies, which prevents the increased output offset
voltage but delivers less gain flatness.
Another straightforward approach is to add a 620Ω resistor
in series with the amplifier’s positive input. This resistor and
the HFA1412 input capacitance form a low pass filter which
rolls off the signal bandwidth before gain peaking occurs.
This configuration was employed to obtain the data sheet AC
and transient parameters for a gain of +1.
Pulse Overshoot
The HFA1412 utilizes a quasi-complementary output stage
to achieve high output current while minimizing quiescent
supply current. In this approach, a composite device
replaces the traditional PNP pulldown transistor. The
composite device switches modes after crossing 0V,
resulting in added distortion for signals swinging below
ground, and an increased overshoot on the negative portion
of the output waveform (see Figure 5, Figure 7, and Figure 9).
This overshoot isn’t present for small bipolar signals (see
Figure 4, Figure 6, and Figure 8) or large positive signals.
Figure 28 through Figure 31 illustrate the amplifier’s
overshoot dependency on input transition time, and signal
polarity.
TABLE 1. UNITY GAIN PERFORMANCE FOR VARIOUS IMPLEMENTATIONS
APPROACH
PEAKING (dB)
BW (MHz)
SR (V/µs)
±0.1dB GAIN FLATNESS (MHz)
Remove -IN Pin
5.0 550 1300
18
+RS = 620Ω
+RS = 620Ω and Remove -IN Pin
Short +IN to -IN (e.g., Pins 2 and 3)
1.0 230 1000
0.7 225 1000
0.1 370 500
25
28
170
100pF Capacitor Between +IN and -IN
0.3 380 550
130
5 FN4152.4
January 23, 2006
5 Page 
HFA1412
Typical Performance Curves VSUPPLY = ±5V, TA = 25°C, RL = 100Ω, Unless Otherwise Specified (Continued)
20
VOUT = +0.5V
15
20
VOUT = +1V
15
10
5
0
100
AV = +1
AV = -1
AV = +2
500
900
1300
1700
INPUT TRANSITION TIME (ps)
2100
FIGURE 28. OVERSHOOT vs TRANSITION TIME
10
5
0
100
AV = +1
AV = -1
AV = +2
500
900
1300
1700
INPUT TRANSITION TIME (ps)
2100
FIGURE 29. OVERSHOOT vs TRANSITION TIME
20
VOUT = 0.5VP-P
15 AV = +1
10
5
0
100
AV = +2
AV = -1
500
900
1300
1700
INPUT TRANSITION TIME (ps)
2100
FIGURE 30. OVERSHOOT vs TRANSITION TIME
20
VOUT = 1VP-P
AV = +1
AV = +2
15
AV = -1
10
5
0
100
500
900
1300
1700
INPUT TRANSITION TIME (ps)
2100
FIGURE 31. OVERSHOOT vs TRANSITION TIME
0.02
0.01
0
-0.01
-0.02
-0.03
-0.04
-0.05
-0.06
-1.5
AV = -1
AV = +1
AV = +2
AV = +2
-1.0 -0.5
0
0.5
INPUT VOLTAGE (V)
1.0
FIGURE 32. INTEGRAL LINEARITY ERROR
1.5
11
0.2
0.1
0.05
0
-0.05
-0.1
-0.2
10 20 30 40 50 60 70 80 90
TIME (ns)
FIGURE 33. SETTLING RESPONSE
FN4152.4
January 23, 2006
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