Offset Adjust. HS-1120RH Datasheet
Radiation Hardened, Ultra High Speed
Current Feedback Ampliﬁer with Offset Adjust
• 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)
• Video Switching and Routing
• Pulse and Video Ampliﬁers
• Wideband Ampliﬁers
• RF/IF Signal Processing
• Flash A/D Driver
• Imaging Systems
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 (RL = 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
html). SMD numbers must be used to order Radiation Hard-
PART NUMBER RANGE (oC) PACKAGE PKG. NO.
5962F9675601VPA -55 to 125 8 Ld CERDIP GDIP1-T8
-40 to 85 8 Ld CERDIP F8.3A
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
Driving Capacitive Loads
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 RF. All current
feedback ampliﬁers require a feedback resistor, even for
unity gain applications, and RF, in conjunction with the
internal compensation capacitor, sets the dominant pole of
the frequency response. Thus, the ampliﬁer’s bandwidth is
inversely proportional to RF. The HS-1120RH design is
optimized for a 510Ω RF at a gain of +1. Decreasing RF in a
unity gain application decreases stability, resulting in
excessive peaking and overshoot. At higher gains the
ampliﬁer is more stable, so RF can be decreased in a trade-
off of stability for bandwidth.
The table below lists recommended RF values for various
gains, and the expected bandwidth.
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!
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 (RS) 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 RS and CL 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.
RS and CL form a low pass network at the output, thus
limiting system bandwidth well below the ampliﬁer band-
width of 850MHz. By decreasing RS as CLincreases (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 AV = +1, RS = 50Ω, CL = 30pF, the overall
bandwidth is limited to 300MHz, and bandwidth drops to
100MHz at AV = +1, RS = 5Ω, CL = 340pF.
40 AV = +1
5 AV = +2
0 40 80 120 160 200 240 280 320
LOAD CAPACITANCE (pF)
FIGURE 1. RECOMMENDED SERIES OUTPUT RESISTOR vs
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
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.
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.
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 (-IBIAS).
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