AN9202: Using the HFA1100, HFA1130 Evaluation Fixture

Using the HFA1100, HFA1130 Evaluation Fixture
Application Note
January 1992
AN9202
General Information
Evaluating the HFA1100
The HFA evaluation fixture is a special purpose board which
frees users from the time-consuming task of developing their
own evaluation hardware. It also serves as an example of
the type of high frequency layout required by ultra high
speed op amps. The board makes no provision for easy
modification to other configurations. Modifications are
strongly discouraged, since surface mount printed circuit
pads tend to disintegrate after only a few resolderings.
As delivered, the fixture is ideal for evaluating the HFA1100.
The VH and VL connections have no effect, since pins 5 and
8 are not bonded out on the HFA1100. Figure 3 details a
setup for evaluating the amplifier’s pulse response, while
Figure 4 illustrates the HFA1100 performance in this setup.
The scope input trace accurately reflects the amplifier input,
but the output trace is one-half the amplifier output voltage.
The fixture is wired in a gain of +2 as shown in Figure 1. It is
intended for use in a 50Ω environment, so input and output termination resistors have been incorporated. Figure 2 illustrates
the typical frequency response of an HFA1100/30 in this fixture.
500Ω
500Ω
VH
50Ω
1
8
2
7
HFA1100/30
IN
10µF
0.1µF
10µF
+5V
50Ω
3
6
OUT
4
5
VL
0.1µF
GND
-5V
GND
FIGURE 1. SCHEMATIC OF HFA1100/30 EVALUATION BOARD
FIGURE 2. HFA1100/30 FREQUENCY RESPONSE (AV = +2)
500Ω
PULSE
GENERATOR
HP8131A OR
EQUIVALENT
VG
50Ω
POWER
SPLITTER
VG
2
+5V
500Ω
–
50Ω
X2
VG
2
VG
2
+
–5V
50Ω
SCOPE
TEK11802 OR
EQUIVALENT
w/50Ω PLUG-IN
FIGURE 3. CONNECTION FOR EVALUATING HFA1100 PULSE RESPONSE
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Application Note 9202
Evaluating the HFA1120
Evaluating the HFA1130
This fixture is not recommended for evaluation of the
HFA1120. The HFA1120 incorporates balance pins (pins 1
and 5) which are absent on the HFA1100. Pin 1 is
unconnected on this fixture, while pin 5 is connected to the
VL terminal. The unequal capacitance on these pins may
unbalance the amplifier and prevent any meaningful
evaluation.
No fixture modifications are necessary when evaluating the
HFA1130. When evaluating unclamped performance, the VH
and VL inputs may be left floating. An unclamped HFA1130
performs like an HFA1100/20 in that the output is clamped to
a default value of approximately ±4.2V. Even though the output swing is less than ±4.2V, the default clamp provides fast
overdrive recovery on the HFA11XX family.
Figure 5 illustrates the HFA1130 clamped pulse response for
a positive pulse. The set-up for evaluating the clamped overdrive recovery time is detailed in Figure 6. This set-up uses a
slower pulse generator, since input transitions ≥2ns yield the
best results.
INPUT AND OUTPUT: 100mV/DIV
INPUT: 200mV/DIV
FIGURE 4. HFA1100 PULSE RESPONSE
OUTPUT: 100mV/DIV
FIGURE 5. HFA1130 CLAMPED PULSE RESPONSE
+1V
PULSE
GENERATOR 0V – 2V
EH136A OR
EQUIVALENT
500Ω VH
50Ω
POWER
SPLITTER
1V
+5V
500Ω
–
1V*
X2
50Ω 0.5V
+
1V
–5V
50Ω
VL
–1V
* DUE TO CLAMP
SCOPE
TEK11802 OR
EQUIVALENT
w/50Ω PLUG-IN
FIGURE 6. CONNECTION FOR EVALUATING HFA1130 OVERDRIVE RECOVERY
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