HS-1120RH
August 1996
Radiation Hardened, Ultra High Speed
Current Feedback Amplifier with Offset Adjust
Description
The HS-1120RH is a radiation hardened, high speed,
wideband, fast settling current feedback amplifier. These
devices are QML approved and are processed and screened
in full compliance with MIL-PRF-38535. Built with Intersil’
proprietary, complementary bipolar UHF-1 (DI bonded
wafer) process, it is the fastest monolithic amplifier available
from any semiconductor manufacturer.
The HS-1120RH’s wide bandwidth, fast settling
characteristic, and low output impedance, make this
amplifier ideal for driving fast A/D converters. Additionally, it
offers offset voltage nulling capabilities as described in the
“Offset Adjustment” section of this datasheet.
Component and composite video systems will also benefit
from this amplifier’s performance, as indicated by the excel-
lent gain flatness, and 0.03%/0.05 Degree Differential
Gain/Phase specifications (R
L
= 75Ω).
Detailed electrical specifications are contained in SMD
5962F9675601VPA, available on the Intersil Website or
AnswerFAX systems (document #967560)
A
Cross Reference Table
is available on the Intersil Website
for conversion of Intersil Part Numbers to SMDs. The address
is (http://www.intersil.com/datasheets/smd/smd_xref.
html).
SMD numbers must be used to order Radiation Hard-
ened Products.
Features
• Electrically Screened to SMD 5962F9675601VPA
• MIL-PRF-38535 Class V Compliant
• Low Distortion (HD3, 30MHz) . . . . . . . . . . -84dBc (Typ)
• Wide -3dB Bandwidth . . . . . . . . . . . . . . . 850MHz (Typ)
• Very High Slew Rate . . . . . . . . . . . . . . . 2300V/µs (Typ)
• Fast Settling (0.1%) . . . . . . . . . . . . . . . . . . . . 11ns (Typ)
• Excellent Gain Flatness (to 50MHz) . . . . . 0.05dB (Typ)
• High Output Current . . . . . . . . . . . . . . . . . . 65mA (Typ)
• Fast Overdrive Recovery. . . . . . . . . . . . . . . <10ns (Typ)
• Total Gamma Dose. . . . . . . . . . . . . . . . . . 300K RAD (Si)
• Latch Up . . . . . . . . . . . . . . . . . . . None (DI Technology)
Applications
• Video Switching and Routing
• Pulse and Video Amplifiers
• Wideband Amplifiers
• RF/IF Signal Processing
• Flash A/D Driver
• Imaging Systems
Ordering Information
PART NUMBER
5962F9675601VPA
HFA1100IJ
(Sample)
HFA11XXEVAL
TEMP.
RANGE (
o
C)
-55 to 125
-40 to 85
PACKAGE
8 Ld CERDIP
8 Ld CERDIP
PKG. NO.
GDIP1-T8
F8.3A
Evaluation Board
Pinout
HS-1120RH
MIL-STD-1835, GDIP1-T8
(CERDIP)
TOP VIEW
BAL
-IN
+IN
V-
1
2
3
4
8
NC
V+
OUT
BAL
-
+
7
6
5
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 321-724-7143 | Copyright © Intersil Corporation 1999
File Number
4101.1
1
HS-1120RH
Application Information
Optimum Feedback Resistor
The enclosed plots of inverting and non-inverting frequency
response illustrate the performance of the HS-1120RH in
various gains. Although the bandwidth dependency on
closed loop gain isn’t as severe as that of a voltage feedback
amplifier, there can be an appreciable decrease in
bandwidth at higher gains. This decrease may be minimized
by taking advantage of the current feedback amplifier’s
unique relationship between bandwidth and R
F
. All current
feedback amplifiers require a feedback resistor, even for
unity gain applications, and R
F
, in conjunction with the
internal compensation capacitor, sets the dominant pole of
the frequency response. Thus, the amplifier’s bandwidth is
inversely proportional to R
F
. The HS-1120RH design is
optimized for a 510Ω R
F
at a gain of +1. Decreasing R
F
in a
unity gain application decreases stability, resulting in
excessive peaking and overshoot. At higher gains the
amplifier is more stable, so R
F
can be decreased in a trade-
off of stability for bandwidth.
The table below lists recommended R
F
values for various
gains, and the expected bandwidth.
GAIN
(A
CL
)
-1
+1
+2
+5
+10
+19
BANDWIDTH
(MHz)
580
850
670
R
S
(Ω)
50
45
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 resis-
tor. The points on the curve indicate the R
S
and C
L
combina-
tions 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.
R
S
and C
L
form a low pass network at the output, thus
limiting system bandwidth well below the amplifier band-
width of 850MHz. By decreasing R
S
as C
L
increases (as
illustrated in the curves), the maximum bandwidth is
obtained without sacrificing stability. Even so, bandwidth
does decrease as you move to the right along the curve.
For example, at A
V
= +1, R
S
= 50Ω, C
L
= 30pF, the overall
bandwidth is limited to 300MHz, and bandwidth drops to
100MHz at A
V
= +1, R
S
= 5Ω, C
L
= 340pF.
R
F
(Ω)
430
510
360
150
180
270
40
35
30
25
20
15
10
A
V
= +1
520
240
125
PC Board Layout
The frequency response of this amplifier depends greatly on
the amount of care taken in designing the PC board.
The
use of low inductance components such as chip resis-
tors 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 (10µF) tantalum in parallel with a small value
(0.1µF) 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.
Care must also be taken to minimize the capacitance to
ground seen by the amplifier’s inverting input (-IN). The
larger this capacitance, the worse the gain peaking, resulting
in pulse overshoot and possible instability. To this end, it is
recommended that the ground plane be removed under
traces connected to -IN, and connections to -IN should be
kept as short as possible.
An example of a good high frequency layout is the Evalua-
tion Board shown in Figure 2.
5 A = +2
V
0
0
40
80
120
160
200
240
280
320
360 400
LOAD CAPACITANCE (pF)
FIGURE 1. RECOMMENDED SERIES OUTPUT RESISTOR vs
LOAD CAPACITANCE
Evaluation Board
The performance of the HS-1120RH may be evaluated using
the HFA11XXEVAL Evaluation Board.
The layout and schematic of the board are shown in
Figure 2. To order evaluation boards, please contact your
local sales office.
Offset Adjustment
The output offset voltage of the HS-1120RH may be nulled via
connections to the BAL pins. Unlike a voltage feedback
amplifier, offset adjustment is accomplished by varying the sign
and/or magnitude of the inverting input bias current (-I
BIAS
).
With voltage feedback amplifiers, bias currents are matched
and bias current induced offset errors are nulled by matching
the impedances seen at the positive and negative inputs. Bias
2
HS-1120RH
currents are uncorrelated on current feedback amplifiers, so
this technique is inappropriate.
-I
BIAS
flows through R
F
causing an output offset error.
Likewise, any change in -I
BIAS
forces a corresponding
change in output voltage, providing the capability for output
offset adjustment. By nulling -I
BIAS
to zero, the offset error
due to this current is eliminated. In addition, an adjustment
limit greater than the -I
BIAS
limit allows the user to null the
contributions from other error sources, such as V
IO
, or +IN
source impedance. For example, the excess adjust current
of 50µA [I
BN
ADJ (Min) - I
BSN
(Max)] allows for the nulling of
an additional 26mV of output offset error (with R
F
= 510Ω) at
room temperature. The amount of adjustment is a function of
R
F
, so adjust range increases with increased R
F
. If allowed
by other considerations, such as bandwidth and noise, R
F
can be increased to provide more adjustment range.
The recommended offset adjustment circuit is shown in
Figure 3.
500
R
1
1
50Ω
IN
0.1µF
-5V
2
3
4
10µF
500
V
H
8
7
50Ω
6
5
GND
GND
OUT
V
L
0.1µF
10µF
+5V
FIGURE 2A. SCHEMATIC
V
H
1
+IN
V
L
OUT
V+
V-
GND
FIGURE 2B. TOP LAYOUT
FIGURE 2C. BOTTOM LAYOUT
FIGURE 2. EVALUATION BOARD SCHEMATIC AND LAYOUT
510
2
-
6
V
IN
HS-1120RH
3 +
5
1
4
10K
V
OUT
V-
FIGURE 3. OFFSET VOLTAGE ADJUSTMENT CIRCUIT
3
HS-1120RH
Typical Performance Characteristics
Device Characterized at: V
SUPPLY
=
±5V,
R
F
= 360Ω, A
V
= +2V/V, R
L
= 100Ω, Unless Otherwise Specified
PARAMETERS
Input Offset Voltage (Note 1)
Average Offset Voltage Drift
V
IO
CMRR
V
IO
PSRR
+Input Current (Note 1)
Average +Input Current Drift
-Input Current (Note 1)
Average -Input Current Drift
-Input Current Adjust Range
+Input Resistance
-Input Resistance
Input Capacitance
Input Noise Voltage (Note 1)
+Input Noise Current (Note 1)
-Input Noise Current (Note 1)
Input Common Mode Range
Open Loop Transimpedance
Output Voltage
A
V
= -1
A
V
= -1, R
L
= 100Ω
A
V
= -1, R
L
= 100Ω
Output Current (Note 1)
A
V
= -1, R
L
= 50Ω
A
V
= -1, R
L
= 50Ω
DC Closed Loop Output Resistance
Quiescent Supply Current (Note 1)
-3dB Bandwidth (Note 1)
R
L
= Open
A
V
= -1, R
F
= 430Ω, V
OUT
= 200mV
P-P
A
V
= +1, R
F
= 510Ω, V
OUT
= 200mV
P-P
A
V
= +2, R
F
= 360Ω, V
OUT
= 200mV
P-P
Slew Rate
A
V
= +1, R
F
= 510Ω, V
OUT
= 5V
P-P
A
V
= +2, V
OUT
= 5V
P-P
Full Power Bandwidth
Gain Flatness (Note 1)
V
OUT
= 5V
P-P
To 30MHz, R
F
= 510Ω
To 50MHz, R
F
= 510Ω
To 100MHz, R
F
= 510Ω
Linear Phase Deviation (Note 1)
2nd Harmonic Distortion (Note 1)
To 100MHz, R
F
= 510Ω
30MHz, V
OUT
= 2V
P-P
50MHz, V
OUT
= 2V
P-P
100MHz, V
OUT
= 2V
P-P
3rd Harmonic Distortion (Note 1)
30MHz, V
OUT
= 2V
P-P
50MHz, V
OUT
= 2V
P-P
100MHz, V
OUT
= 2V
P-P
3rd Order Intercept (Note 1)
1dB Compression
Reverse Isolation (S
12
)
100MHz, R
F
= 510Ω
100MHz, R
F
= 510Ω
40MHz, R
F
= 510Ω
100MHz, R
F
= 510Ω
600MHz, R
F
= 510Ω
f = 100kHz
f = 100kHz
f = 100kHz
VCM = 0V
Versus Temperature
∆V
CM
=
±2V
∆V
S
=
±1.25V
VCM = 0V
Versus Temperature
VCM = 0V
Versus Temperature
VCM = 0V
∆V
CM
=
±2V
CONDITIONS
TEMPERATURE
+25
o
C
Full
+25
o
C
+25
o
C
+25
o
C
Full
+25
o
C
Full
+25
o
C
+25
o
C
+25
o
C
+25
o
C
+25
o
C
+25
o
C
+25
o
C
Full
+25
o
C
+25
o
C
Full
+25
o
C to +125
o
C
-55
o
C to 0
o
C
+25
o
C
Full
+25
o
C
+25
o
C
+25
o
C
+25
o
C
+25
o
C
+25
o
C
+25
o
C
+25
o
C
+25
o
C
+25
o
C
+25
o
C
+25
o
C
+25
o
C
+25
o
C
+25
o
C
+25
o
C
+25
o
C
+25
o
C
+25
o
C
+25
o
C
+25
o
C
TYPICAL
2
10
46
50
25
40
12
40
±200
50
16
2.2
4
18
21
±3.0
500
±3.3
±3.0
±65
±50
0.1
24
580
850
670
1500
2300
220
±0.014
±0.05
±0.14
±0.6
-55
-49
-44
-84
-70
-57
30
20
-70
-60
-32
UNITS
mV
µV/
o
C
dB
dB
µA
nA/
o
C
µA
nA/
o
C
µA
kΩ
Ω
pF
nV/√Hz
pA/√Hz
pA/√Hz
V
kΩ
V
V
mA
mA
Ω
mA
MHz
MHz
MHz
V/µs
V/µs
MHz
dB
dB
dB
Degrees
dBc
dBc
dBc
dBc
dBc
dBc
dBm
dBm
dB
dB
dB
4
HS-1120RH
Typical Performance Characteristics
PARAMETERS
Rise and Fall Time
(Continued)
Device Characterized at: V
SUPPLY
=
±5V,
R
F
= 360Ω, A
V
= +2V/V, R
L
= 100Ω, Unless Otherwise Specified
(Continued)
CONDITIONS
V
OUT
= 0.5V
P-P
V
OUT
= 2V
P-P
Overshoot (Note 1)
Settling Time (Note 1)
V
OUT
= 0.5V
P-P
, Input t
R
/t
F
= 550ps
To 0.1%, V
OUT
= 2V to 0V, R
F
= 510Ω
To 0.05%, V
OUT
= 2V to 0V, R
F
= 510Ω
To 0.02%, V
OUT
= 2V to 0V, R
F
= 510Ω
Differential Gain
Differential Phase
Overdrive Recovery Time
NOTE:
1. See Typical Performance Curve for more information.
A
V
= +2, R
L
= 75Ω, NTSC
A
V
= +2, R
L
= 75Ω, NTSC
R
F
= 510Ω, V
IN
= 5V
P-P
TEMPERATURE
+25
o
C
+25
o
C
+25
o
C
+25
o
C
+25
o
C
+25
o
C
+25
o
C
+25
o
C
+25
o
C
TYPICAL
500
800
11
11
19
34
0.03
0.05
7.5
UNITS
ps
ps
%
ns
ns
ns
%
Degrees
ns
Typical Performance Curves
V
SUPPLY
=
±5V,
R
F
= 510Ω, R
L
= 100Ω, T
A
= +25
o
C, Unless Otherwise Specified
120
90
OUTPUT VOLTAGE (mV)
60
30
0
-30
-60
-90
-120
5ns/DIV.
OUTPUT VOLTAGE (V)
1.2
0.9
0.6
0.3
0
-0.3
-0.6
-0.9
-1.2
5ns/DIV.
FIGURE 4. SMALL SIGNAL PULSE RESPONSE (A
V
= +2)
FIGURE 5. LARGE SIGNAL PULSE RESPONSE (A
V
= +2)
GAIN (dB) NORMALIZED
0
-3
-6
-9
-12
GAIN
A
V
= +1
A
V
= +2
A
V
= +6
A
V
= +11
PHASE (DEGREES)
PHASE
A
V
= +1
A
V
= +2
A
V
= +6
A
V
= +11
0.3
1
10
100
FREQUENCY (MHz)
1K
0
-90
-180
-270
-360
GAIN (dB) NORMALIZED
0
-3
-6
-9
-12
GAIN
A
V
= -1
A
V
= -5
A
V
= -10
A
V
= -20
180
A
V
= -1
A
V
= -5
A
V
= -10
A
V
= -20
90
0
-90
-180
1K
PHASE (DEGREES)
PHASE
0.3
1
10
100
FREQUENCY (MHz)
FIGURE 6. NON-INVERTING FREQUENCY RESPONSE
(V
OUT
= 200mV
P-P
)
FIGURE 7. INVERTING FREQUENCY RESPONSE
(V
OUT
= 200mV
P-P
)
5
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