1
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 321-724-7143
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Copyright
Intersil Corporation 1999
HFA1412
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 (R
L
= 150
). Its ability to deliver a gain of +2
with no external resistors makes it particularly desirable for
applications driving double terminated cables.
For Military product, refer to the HFA1412/883 data sheet.
Pinout
HFA1412
(PDIP, SOIC)
TOP VIEW
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/
s
Fast Settling Time (0.1%) . . . . . . . . . . . . . . . . . . . . . 28ns
High Output Current . . . . . . . . . . . . . . . . . . . . . . . . . 55mA
Excellent Gain Accuracy . . . . . . . . . . . . . . . . . . . 0.99V/V
Overdrive Recovery . . . . . . . . . . . . . . . . . . . . . . . . <10ns
Standard Operational Amplifier Pinout
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
Functional Diagram
Ordering Information
PART NUMBER
TEMP.
RANGE (
o
C)
PACKAGE
PKG.
NO.
HFA1412IP
-40 to 85
14 Ld PDIP
E14.3
HFA1412IB
-40 to 85
14 Ld SOIC
M14.15
HA5025EVAL
DIP Evaluation Board For Quad Op Amp
OUT1
-IN1
+IN1
V+
+IN2
-IN2
OUT2
OUT4
-IN4
+IN4
V-
+IN3
-IN3
OUT3
1
2
3
4
5
6
7
14
13
12
11
10
9
8
OUT4
OUT3
-
+
OUT1
425
425
OUT2
1
7
8
14
2
3
6
5
9
10
13
12
-IN1
+IN1
-IN2
+IN2
-IN3
-IN4
+IN4
+IN3
-
+
425
425
-
+
425
425
-
+
425
425
Data Sheet
September 1998
File Number
4152.2
2
Absolute Maximum Ratings
Thermal Information
Voltage Between V+ and V- . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11V
DC Input Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . V
SUPPLY
Output Current (Note 1) . . . . . . . . . . . . . . . . Short Circuit Protected
ESD Rating
Human Body Model (Per MIL-STD-883 Method 3015.7) . . . .600V
Operating Conditions
Temperature Range . . . . . . . . . . . . . . . . . . . . . . . . . . -40
o
C to 85
o
C
Thermal Resistance (Typical, Note 2)
JA
(
o
C/W)
PDIP Package . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
100
SOIC Package . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
120
Maximum Junction Temperature (Die) . . . . . . . . . . . . . . . . . . .175
o
C
Maximum Junction Temperature (Plastic Package) . . . . . . . .150
o
C
Maximum Storage Temperature Range . . . . . . . . . . -65
o
C to 150
o
C
Maximum Lead Temperature (Soldering 10s) . . . . . . . . . . . . 300
o
C
(SOIC-Lead Tips Only)
CAUTION: Stresses above those listed in "Absolute Maximum Ratings" may cause permanent damage to the device. This is a stress only rating and operation of the
device at these or any other conditions above those indicated in the operational sections of this specification is not implied.
NOTES:
1. Output is protected for short circuits to ground. Brief short circuits to ground will not degrade reliability, however, continuous (100% duty cycle)
output current should not exceed 30mA for maximum reliability.
2.
JA
is measured with the component mounted on an evaluation PC board in free air.
Electrical Specifications
V
SUPPLY
=
5V, A
V
= +1, R
L
= 100
,
Unless Otherwise Specified.
PARAMETER
TEST
CONDITIONS
(NOTE 3)
TEST
LEVEL
TEMP
(
o
C)
MIN
TYP
MAX
UNITS
INPUT CHARACTERISTICS
Output Offset Voltage
A
25
-
2
10
mV
A
Full
-
3
15
mV
Average Output Offset Voltage Drift
B
Full
-
22
70
V/
o
C
Channel-to-Channel Output Offset
Voltage Mismatch
A
25
-
-
15
mV
A
Full
-
-
30
mV
Common-Mode Rejection Ratio
V
CM
=
1.8V
A
25
42
45
-
dB
V
CM
=
1.8V
A
85
40
44
-
dB
V
CM
=
1.2V
A
-40
40
45
-
dB
Power Supply Rejection Ratio
V
PS
=
1.8V
A
25
45
49
-
dB
V
PS
=
1.8V
A
85
43
48
-
dB
V
PS
=
1.2V
A
-40
43
48
-
dB
Non-Inverting Input Bias Current
A
25
-
1
15
A
A
Full
-
3
25
A
Non-Inverting Input Bias Current Drift
B
Full
-
30
80
nA/
o
C
Channel-to-Channel Non-Inverting Input
Bias Current Mismatch
A
25
-
-
15
A
A
Full
-
-
25
A
Non-Inverting Input Bias Current Power
Supply Sensitivity
V
PS
=
1.25V
A
25
-
0.5
1
A/V
A
Full
-
-
3
A/V
Non-Inverting Input Resistance
V
CM
=
1.8V
A
25
0.8
1.1
-
M
V
CM
=
1.8V
A
85
0.5
1.4
-
M
V
CM
=
1.2V
A
-40
0.5
1.3
-
M
Inverting Input Resistance
C
25
-
425
-
Input Capacitance (either input)
C
25
-
2
-
pF
Input Voltage Common Mode Range
(Implied by V
IO
CMRR and +R
IN
tests)
A
25, 85
1.8
2.4
-
V
A
-40
1.2
1.7
-
V
Input Noise Voltage Density (Note 4)
f = 100kHz
B
25
-
7
-
nV/
Hz
Non-Inverting Input Noise Current
Density (Note 4)
f = 100kHz
B
25
-
3
-
pA/
Hz
HFA1412
3
TRANSFER CHARACTERISTICS
Gain (V
IN
= -1V to +1V)
A
V
= -1
A
25
-0.98
-0.996
-1.02
V/V
A
Full
-0.975
-1.000
-1.025
V/V
A
V
= +1
A
25
0.98
0.992
1.02
V/V
A
Full
0.975
0.993
1.025
V/V
A
V
= +2
A
25
1.96
1.988
2.04
V/V
A
Full
1.95
1.990
2.05
V/V
Channel-to-Channel Gain Mismatch
A
V
= -1
A
25
-
-
0.02
V/V
A
Full
-
-
0.025
V/V
A
V
= +1
A
25
-
-
0.025
V/V
A
Full
-
-
0.025
V/V
A
V
= +2
A
25
-
-
0.04
V/V
A
Full
-
-
0.05
V/V
AC CHARACTERISTICS
-3dB Bandwidth
(V
OUT
= 0.2V
P-P
, Note 4)
A
V
= -1
B
25
200
320
-
MHz
B
Full
190
280
-
MHz
A
V
= +1,
+R
S
= 620
B
25
160
230
-
MHz
B
Full
150
210
-
MHz
A
V
= +2
B
25
220
350
-
MHz
B
Full
190
300
-
MHz
Full Power Bandwidth
(V
OUT
= 5V
P-P
at A
V
= +2 or -1,
V
OUT
= 4V
P-P
at A
V
= +1, Note 4)
A
V
= -1
B
25
-
225
-
MHz
A
V
= +1,
+R
S
= 620
B
25
-
190
-
MHz
A
V
= +2
B
25
-
160
-
MHz
Gain Flatness
(V
OUT
= 0.2V
P-P
, Note 4)
A
V
= +1,
to 25MHz,
+R
S
= 620
B
25
-
0.10
0.18
dB
B
Full
-
0.12
0.20
dB
A
V
= -1,
to 50MHz
B
25
-
0.06
0.10
dB
B
Full
-
0.08
0.16
dB
A
V
= -1,
to 100MHz
B
25
-
0.08
0.20
dB
B
Full
-
0.13
0.30
dB
A
V
= +2,
to 50MHz
B
25
-
0.05
0.09
dB
B
Full
-
0.06
0.10
dB
A
V
= +2,
to 100MHz
B
25
-
0.08
0.16
dB
B
Full
-
0.16
0.30
dB
Crosstalk
(All Channels Hostile, Note 4)
5MHz
B
25
-
-53
-
dB
10MHz
B
25
-
-50
-
dB
OUTPUT CHARACTERISTICS
Output Voltage Swing
(Note 4)
A
V
= -1
A
25
3.0
3.2
-
V
A
Full
2.8
3.0
-
V
Output Current
(Note 4)
A
V
= -1, R
L
= 50
A
25, 85
50
55
-
mA
A
-40
28
42
-
mA
Electrical Specifications
V
SUPPLY
=
5V, A
V
= +1, R
L
= 100
,
Unless Otherwise Specified. (Continued)
PARAMETER
TEST
CONDITIONS
(NOTE 3)
TEST
LEVEL
TEMP
(
o
C)
MIN
TYP
MAX
UNITS
HFA1412
4
Output Short Circuit Current
B
25
-
100
-
mA
DC Closed Loop Output Impedance
A
V
= +2
B
25
-
0.2
-
Second Harmonic Distortion
(A
V
= +2, V
OUT
= 2V
P-P
, Note 4)
10MHz
B
25
-47
-50
-
dBc
B
Full
-45
-48
-
dBc
20MHz
B
25
-40
-43
-
dBc
B
Full
-39
-41
-
dBc
Third Harmonic Distortion
(A
V
= +2, V
OUT
= 2V
P-P
, Note 4)
10MHz
B
25
-55
-60
-
dBc
B
Full
-55
-60
-
dBc
20MHz
B
25
-46
-53
-
dBc
B
Full
-46
-50
-
dBc
Reverse Isolation (S
12
, Note 4)
30MHz, A
V
= +2
B
25
-
-65
-
dB
TRANSIENT RESPONSE A
V
= +2, Unless Otherwise Specified
Rise and Fall Times
(V
OUT
= 0.5V
P-P
)
Rise Time
B
25
-
1.0
-
ns
Fall Time
B
25
-
1.25
-
ns
Overshoot
(V
OUT
= 0.5V
P-P
, V
IN
t
RISE
= 500ps,
Notes 4, 5)
+OS
B
25
-
3
-
%
-OS
B
25
-
9
-
%
Slew Rate
(V
OUT
= 5V
P-P
at A
V
= +2 or -1,
V
OUT
= 4V
P-P
at A
V
= +1)
A
V
= -1
B
25
1150
1700
-
V/
s
B
Full
1100
1650
-
V/
s
A
V
= +1,
+R
S
= 620
B
25
700
1000
-
V/
s
B
Full
650
950
-
V/
s
A
V
= +2
B
25
900
1250
-
V/
s
B
Full
800
1150
-
V/
s
Settling Time
(V
OUT
= +2V to 0V Step, Note 4)
To 0.1%
B
25
-
28
-
ns
To 0.05%
B
25
-
33
-
ns
To 0.02%
B
25
-
38
-
ns
Overdrive Recovery Time
V
IN
=
2V
B
25
-
8.5
-
ns
VIDEO CHARACTERISTICS
Differential Gain (f = 3.58MHz, A
V
= +2)
R
L
= 150
B
25
-
0.03
-
%
R
L
= 75
B
25
-
0.05
-
%
Differential Phase (f = 3.58MHz, A
V
= +2)
R
L
= 150
B
25
-
0.02
-
Degrees
R
L
= 75
B
25
-
0.05
-
Degrees
POWER SUPPLY CHARACTERISTICS
Power Supply Range
C
25
4.5
-
5.5
V
Power Supply Current (Note 4)
A
25
-
5.9
6.1
mA/Op Amp
A
Full
-
6.1
6.3
mA/Op Amp
NOTES:
3. Test Level: A. Production Tested; B. Typical or Guaranteed Limit Based on Characterization; C. Design Typical for Information Only.
4. See Typical Performance Curves for more information.
5. Negative overshoot dominates for output signal swings below GND (e.g. 0.5V
P-P
), yielding a higher overshoot limit compared to the
V
OUT
= 0V to 0.5V condition. See the "Application Information" section for details.
Electrical Specifications
V
SUPPLY
=
5V, A
V
= +1, R
L
= 100
,
Unless Otherwise Specified. (Continued)
PARAMETER
TEST
CONDITIONS
(NOTE 3)
TEST
LEVEL
TEMP
(
o
C)
MIN
TYP
MAX
UNITS
HFA1412
5
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 50
resistor.
The table below summarizes these connections:
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 620
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.
GAIN
(A
CL
)
CONNECTIONS
+INPUT
-INPUT
-1
50
to GND
Input
+1
Input
NC (Floating)
+2
Input
GND
TABLE 1. UNITY GAIN PERFORMANCE FOR VARIOUS IMPLEMENTATIONS
APPROACH
PEAKING (dB)
BW (MHz)
SR (V/
s)
0.1dB GAIN FLATNESS (MHz)
Remove -IN Pin
5.0
550
1300
18
+R
S
= 620
1.0
230
1000
25
+R
S
= 620
and Remove -IN Pin
0.7
225
1000
28
Short +IN to -IN (e.g., Pins 2 and 3)
0.1
370
500
170
100pF Capacitor Between +IN and -IN
0.3
380
550
130
HFA1412
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