Feedback Amplifier. HS7-1100RH-Q Datasheet
August 1999 File Number 4100.2
Radiation Hardened, Ultra High Speed
Current Feedback Ampliﬁer
The HS-1100RH is a radiation hardened high speed,
wideband, fast settling current feedback ampliﬁer. Built with
Intersil’s proprietary, complementary bipolar UHF-1 (DI
bonded wafer) process, it is the fastest monolithic ampliﬁer
available from any semiconductor manufacturer. These
devices are QML approved and are processed and screened
in full compliance with MIL-PRF-38535.
The HS-1100RH’s wide bandwidth, fast settling characteristic,
and low output impedance make this amplifier ideal for driving
fast A/D converters.
Component and composite video systems will also beneﬁt
from this ampliﬁer’s performance, as indicated by the
excellent gain ﬂatness, and 0.03%/0.05 Deg. Differential
Gain/Phase speciﬁcations (RL = 75Ω).
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 5962-94676. A “hot-link” is provided
on our homepage for downloading.
HFA1100IJ (Sample) HFA1100IJ
-55 to 125
-55 to 125
-40 to 85
• Electrically Screened to SMD # 5962-94676
• QML Qualiﬁed per MIL-PRF-38535 Requirements
• 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. . . . . . . . . . . . . . . . . . . . 300kRAD(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
OR CDIP2-T8 (SBDIP)
1 CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 321-724-7143 | Copyright © Intersil Corporation 1999
Optimum Feedback Resistor
The enclosed plots of inverting and non-inverting frequency
response illustrate the performance of the HS-1100RH 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-1100RH
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
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 (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
Evaluation Board shown in Figure 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 (RS) 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 RS and CL
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.
40 AV = +1
5 AV = +2
120 160 200 240 280 320
LOAD CAPACITANCE (pF)
FIGURE 1. RECOMMENDED SERIES OUTPUT RESISTOR vs
RS and CL form a low pass network at the output, thus
limiting system bandwidth well below the ampliﬁer bandwidth
of 850MHz. By decreasing RS as CL 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 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.
The performance of the HS-1100RH 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.