DATASHEET
HS-1412RH
Radiation Hardened, Quad, High Speed, Low Power, Video Closed Loop Buffer
The HS-1412RH is a radiation hardened quad closed loop
buffer featuring user programmable gain and high speed
performance. Manufactured on Intersil’s proprietary
complementary bipolar UHF-1 (DI bonded wafer) process,
this device offers wide -3dB bandwidth of 340MHz, very fast
slew rate, excellent gain flatness and high output current.
These devices are QML approved and are processed and
screened in full compliance with MIL-PRF-38535.
A unique feature of the pinout allows the user to select a
voltage gain of +1, -1, or +2, without the use of any external
components. Gain selection is accomplished via
connections to the inputs, as described in the “Application
Information” section. The result is a more flexible product,
fewer part types in inventory, and more efficient use of board
space.
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.
Specifications for Rad Hard QML devices are controlled
by the Defense Supply Center in Columbus (DSCC). The
SMD numbers listed here must be used when ordering.
Detailed Electrical Specifications for these devices are
contained in SMD 5962-96834. A “hot-link” is provided
on our homepage for downloading.
www.intersil.com/spacedefense/space.asp
FN4230
Rev 1.00
August 1999
Features
• Electrically Screened to SMD # 5962-96834
• QML Qualified per MIL-PRF-38535 Requirements
• MIL-PRF-38535 Class V Compliant
• User Programmable For Closed-Loop Gains of +1, -1 or
+2 Without Use of External Resistors
• Standard Operational Amplifier Pinout
• Low Supply Current . . . . . . . . . . . . 5.9mA/Op Amp (Typ)
• Excellent Gain Accuracy . . . . . . . . . . . . . . . 0.99V/V (Typ)
• Wide -3dB Bandwidth. . . . . . . . . . . . . . . . . 340MHz (Typ)
• Fast Slew Rate. . . . . . . . . . . . . . . . . . . . . .1155V/s (Typ)
• High Input Impedance . . . . . . . . . . . . . . . . . . . 1M (Typ)
• Excellent Gain Flatness (to 50MHz). . . . . .
0.02dB
(Typ)
• Fast Overdrive Recovery . . . . . . . . . . . . . . . . <10ns (Typ)
• Total Gamma Dose . . . . . . . . . . . . . . . . . . . 300kRAD(Si)
• Latch Up. . . . . . . . . . . . . . . . . . . . . None (DI Technology)
Applications
• Flash A/D Driver
• Video Switching and Routing
• Pulse and Video Amplifiers
• Wideband Amplifiers
• RF/IF Signal Processing
Ordering Information
ORDERING NUMBER
5962F9683401VCA
5962F9683401VCC
INTERNAL
MKT. NUMBER
HS1-1412RH-Q
HS1B-1412RH-Q
TEMP. RANGE
(
o
C)
-55 to 125
-55 to 125
• Imaging Systems
Pinout
HS-1412RH (CERDIP) GDIP1-T14
OR
HS-1412RH (SBDIP) CDIP2-T14
TOP VIEW
OUT1 1
-IN1 2
+IN1 3
V+ 4
+IN2 5
-IN2 6
OUT2 7
14 OUT4
13 -IN4
12 +IN4
11 V-
10 +IN3
9 -IN3
8 OUT3
FN4230 Rev 1.00
August 1999
Page 1 of 11
HS-1412RH
Application Information
HS-1412RH Advantages
The HS-1412RH 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 HS-1412RH 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 HS-1412RH
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 HS-1412RH’s closed loop gain implementation provides
better gain accuracy, lower offset and output impedance, and
better distortion compared with open loop buffers.
Unity Gain Considerations
Unity gain selection is accomplished by floating the -Input of
the HS-1412RH. 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
HS-1412RH 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
HS-1412RH 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.
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:
GAIN
(A
CL
)
-1
+1
+2
CONNECTIONS
+INPUT
50
to GND
Input
Input
-INPUT
Input
NC (Floating)
GND
Pulse Overshoot
The HS-1412RH 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
Remove -IN Pin
+R
S
= 620
+R
S
= 620and Remove -IN Pin
Short +IN to -IN (e.g., Pins 2 and 3)
100pF Capacitor Between +IN and -IN
PEAKING (dB)
5.0
1.0
0.7
0.1
0.3
BW (MHz)
550
230
225
370
380
SR (V/s)
1300
1000
1000
500
550
0.1dB
GAIN FLATNESS (MHz)
18
25
28
170
130
FN4230 Rev 1.00
August 1999
Page 2 of 11
HS-1412RH
PC Board Layout
This amplifier’s frequency response depends greatly on the
care taken in designing the PC board (PCB).
The use of low
inductance components such as chip resistors and chip
capacitors is strongly recommended, while a solid ground
plane is a must!
Attention should be given to decoupling the power supplies. A
large value (10F) tantalum in parallel with a small value
(0.1F) chip capacitor works well in most cases.
Terminated microstrip signal lines are recommended at the
input and output of the device. Capacitance directly on the
output must be minimized, or isolated as discussed in the next
section.
An example of a good high frequency layout is the Evaluation
Board shown in Figure 3.
Evaluation Board
The performance of the HS-1412RH may be evaluated using
the HA5025 Evaluation Board, slightly modified as follows:
1. Remove the four feedback resistors, and leave the
connections open.
2. a. For A
V
= +1 evaluation, remove the gain setting
resistors (R
1
), and leave pins 2, 6, 9, and 13 floating.
b. For A
V
= +2, replace the gain setting resistors (R
1
) with
0 resistors to GND.
The modified schematic for amplifier 1, and the board layout
are shown in Figures 2 and 3.
To order evaluation boards (part number HA5025EVAL),
please contact your local sales office.
50
OUT
R
1
(NOTE)
IN
50
1
2
3
4
5
0.1F 6
7
-
+
14
13
12
11
10
9
8
GND
GND
0.1F
-5V
10F
NOTE: R
1
=
(A
V
= +1)
or 0 (A
V
= +2)
Driving Capacitive Loads
Capacitive loads, such as an A/D input, or an improperly
terminated transmission line will degrade the amplifier’s phase
margin resulting in frequency response peaking and possible
oscillations. In most cases, the oscillation can be avoided by
placing a resistor (R
S
) in series with the output prior to the
capacitance.
Figure 1 details starting points for the selection of this resistor.
The points on the curve indicate the R
S
and C
L
combinations
for the optimum bandwidth, stability, and settling time, but
experimental fine tuning is recommended. Picking a point
above or to the right of the curve yields an overdamped
response, while points below or left of the curve indicate areas
of underdamped performance.
50
SERIES OUTPUT RESISTANCE ()
+5V
10F
FIGURE 2. MODIFIED EVALUATION BOARD SCHEMATIC
40
30
20
A
V
= +2
A
V
= +1
FIGURE 3A. TOP LAYOUT
10
0
0
50
100
150
200
250
300
350
400
LOAD CAPACITANCE (pF)
FIGURE 1. RECOMMENDED SERIES RESISTOR vs LOAD
CAPACITANCE
R
S
and C
L
form a low pass network at the output, thus limiting
system bandwidth well below the amplifier bandwidth of
350MHz. By decreasing R
S
as C
L
increases (as illustrated in the
curves), the maximum bandwidth is obtained without sacrificing
stability. In spite of this, bandwidth decreases as the load
capacitance increases. For example, at A
V
= +2, R
S
= 22,
C
L
= 100pF, the overall bandwidth is 125MHz, and bandwidth
drops to 100MHz at R
S
= 12, C
L
= 220pF.
FIGURE 3B. BOTTOM LAYOUT
FIGURE 3. EVALUATION BOARD LAYOUT
FN4230 Rev 1.00
August 1999
Page 3 of 11
HS-1412RH
Typical Performance Curves
200
A
V
= +2
150
OUTPUT VOLTAGE (mV)
V
SUPPLY
=
5V,
T
A
= 25
o
C, R
L
= 100, Unless Otherwise Specified
2.0
A
V
= +2
1.5
OUTPUT VOLTAGE (V)
1.0
0.5
0
-0.5
-1.0
-1.5
-2.0
100
50
0
-50
-100
-150
-200
TIME (5ns/DIV.)
TIME (5ns/DIV.)
FIGURE 4. SMALL SIGNAL PULSE RESPONSE
FIGURE 5. LARGE SIGNAL PULSE RESPONSE
200
150
OUTPUT VOLTAGE (mV)
100
50
0
-50
-100
-150
-200
TIME (5ns/DIV.)
A
V
= +1
2.0
1.5
OUTPUT VOLTAGE (V)
1.0
0.5
0
-0.5
-1.0
-1.5
-2.0
TIME (5ns/DIV.)
A
V
= +1
FIGURE 6. SMALL SIGNAL PULSE RESPONSE
FIGURE 7. LARGE SIGNAL PULSE RESPONSE
200
A
V
= -1
150
OUTPUT VOLTAGE (mV)
OUTPUT VOLTAGE (V)
100
50
0
-50
-100
-150
-200
TIME (5ns/DIV.)
2.0
A
V
= -1
1.5
1.0
0.5
0
-0.5
-1.0
-1.5
-2.0
TIME (5ns/DIV.)
FIGURE 8. SMALL SIGNAL PULSE RESPONSE
FIGURE 9. LARGE SIGNAL PULSE RESPONSE
FN4230 Rev 1.00
August 1999
Page 4 of 11
HS-1412RH
Typical Performance Curves
NORMALIZED GAIN (dB)
6
3
0
-3
-6
PHASE
GAIN
V
OUT
= 200mV
P-P
V
SUPPLY
=
5V,
T
A
= 25
o
C, R
L
= 100, Unless Otherwise Specified
(Continued)
A
V
= +2, V
OUT
= 200mV
P-P
9
GAIN (dB)
A
V
= +2
6
3
0
A
V
= -1
PHASE (DEGREES)
A
V
= +1
A
V
= +2
0
90
A
V
= -1
A
V
= +1
180
270
500
GAIN
R
L
= 1k
R
L
= 100
R
L
= 50
0
R
L
= 1k
R
L
= 100
R
L
= 50
90
180
270
100
500
PHASE (DEGREES)
PHASE (DEGREES)
PHASE (DEGREES)
PHASE
0.3
1
10
FREQUENCY (MHz)
100
0.3
1
10
FREQUENCY (MHz)
FIGURE 10. FREQUENCY RESPONSE
FIGURE 11. FREQUENCY RESPONSE FOR VARIOUS LOAD
RESISTORS
3
GAIN (dB)
0
-3
-6
A
V
= +1, V
OUT
= 200mV
P-P
GAIN (dB)
3
0
-3
-6
A
V
= -1, V
OUT
= 200mV
P-P
GAIN
R
L
= 1k
R
L
= 100
R
L
= 50
PHASE
R
L
= 1k
R
L
= 100
R
L
= 50
0
90
180
270
100
500
PHASE (DEGREES)
GAIN
R
L
= 1k
R
L
=100
R
L
= 50
PHASE
R
L
= 1k
R
L
= 100
R
L
= 50
180
90
0
-90
500
0.3
1
10
FREQUENCY (MHz)
0.3
1
10
FREQUENCY (MHz)
100
FIGURE 12. FREQUENCY RESPONSE FOR VARIOUS LOAD
RESISTORS
FIGURE 13. FREQUENCY RESPONSE FOR VARIOUS LOAD
RESISTORS
9
GAIN (dB)
6
3
0
A
V
= +2
GAIN (dB)
3
0
-3
-6
A
V
= +1
GAIN
1V
P-P
2.5V
P-P
4V
P-P
0
1V
P-P
2.5V
P-P
4V
P-P
90
180
270
100
360
500
PHASE (DEGREES)
GAIN
1V
P-P
2.5V
P-P
4V
P-P
PHASE
1V
P-P
2.5V
P-P
4V
P-P
0
90
180
270
100
360
500
PHASE
0.3
1
10
FREQUENCY (MHz)
0.3
1
10
FREQUENCY (MHz)
FIGURE 14. FREQUENCY RESPONSE FOR VARIOUS OUTPUT
VOLTAGES
FIGURE 15. FREQUENCY RESPONSE FOR VARIOUS OUTPUT
VOLTAGES
FN4230 Rev 1.00
August 1999
Page 5 of 11
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