HFA3-0001-5 INTERSIL [Intersil Corporation], HFA3-0001-5 Datasheet - Page 9

• Manufacturer Part Number: HFA3-0001-5
• Description: Ultra High Slew RateOperational Amplifier
• Manufacturer: INTERSIL [Intersil Corporation]

Applications Information
Offset Adjustment
When applications require the offset voltage to be as low as
possible, the figure below shows two possible schemes for
adjusting offset voltage.
For a voltage follower application, use the circuit in Figure 29
without R
The adjustment resistors will cause only a very small gain error.
PC Board Layout Guidelines
When designing with the HFA-0001, good high frequency
(RF) techniques should be used when making a PC board. A
massive ground plane should be used to maintain a low
impedance ground. Proper shielding and use of short
interconnection leads are also very important.
To achieve maximum high frequency performance, the use
of low impedance transmission lines with impedance
matching is recommended: 50Ω lines are common in
communications and 75Ω lines in video systems. Impedance
matching is important to minimize reflected energy therefore
minimizing transmitted signal distortion. This is
accomplished by using a series matching resistor (50Ω or
75Ω), matched transmission line (50Ω or 75Ω), and a
matched terminating resistor, as shown in Figure 30. Note
that there will be a 6dB loss from input to output.The HFA-
0001 has an integral 50Ω ±20% resistor connected to the op
amps output with the other end of the resistor pinned out.
50kΩ
Adjustment Range
50kΩK
+V
2
-V
and with R
+5V
-5V
FIGURE 29. NON-INVERTING GAIN
100kΩ
FIGURE 28. INVERTING GAIN
V
R
Adjustment Range
IN
1
I
≅
shorted. R
±
100Ω
100kΩ
V
R
R
R
2


V
I
1
R 2
-------
R
IN
R
1
I



9
1
100
should be 1MΩ to 10MΩ.
≅
R
2
±
Gain 1
V
+


R
-
R 2
-------
R
F
+
-
R
1
≅
F



+


------------------- -
R
I
R
+
V
F
OUT
R
V
OUT
2



HFA-0001
This 50Ω resistor can be used as the series resistor instead
of an external resistor.
PC board traces can be made to look like a 50Ω or 75Ω
transmission line, called microstrip. Microstrip is a PC board
trace with a ground plane directly beneath, on the opposite
side of the board, as shown in Figure 31.
When manufacturing pc boards, the trace width can be
calculated based on a number of variables. The following
equation is reasonably accurate for calculating the proper
trace width for a 50Ω transmission line.
Power supply decoupling is essential for high frequency op
amps. A 0.01µF high quality ceramic capacitor at each
supply pin in parallel with a 1µF tantalum capacitor will
provide excellent decoupling as shown in Figure 32.
V
IN
GROUND
PLANE
50
+
R
FIGURE 32. POWER SUPPLY DECOUPLING
F
SIGNAL
TRACE
Z
h
O
=
50Ω
------------------------------ ln
E
R
FIGURE 30.
FIGURE 31.
87
+
+
1.41
w
V+
V-
50Ω COAX CABLE
0.01µF
0.01µF
1.0µF
1.0µF
E

-------------------- -
0.8w
R
5.98h
+
t


DIELECTRIC
(PC BOARD)
Ω
t
50Ω
V
OUT