BUF600 Datasheet, PDF (10/14 Pages) Burr-Brown (TI) – HIGH-SPEED BUFFER AMPLIFIER

The buffer outputs are not current-limited or protected. If the
output is shorted to ground, high currents could arise when
the input voltage is ±3.6V. Momentary shorts to ground (a
few seconds) should be avoided but are unlikely to cause
permanent damage.
CIRCUIT LAYOUT
The high-frequency performance of the BUF600 and BUF601
can be greatly affected by the physical layout of the printed
circuit board. The following tips are offered as suggestions,
not as absolute musts. Oscillations, ringing, poor bandwidth
and settling, and peaking are all typical problems that plague
high-speed components when they are used incorrectly.
• Bypass power supplies very close to the device pins. Use
tantalum chip capacitors (approximately 2.2µF); a paral-
lel 470nF ceramic chip capacitor may be added if desired.
Surface-mount types are recommended due to their low
lead inductance.
• PC board traces for power lines should be wide to reduce
impedance or inductance.
• Make short and low inductance traces. The entire physi-
cal circuit should be as small as possible.
• Use a low-impedance ground plane on the component
side to ensure that low-impedance ground is available
throughout the layout.
• Do not extend the ground plane under high-impedance
nodes sensitive to stray capacitances, such as the buffer’s
input terminals.
• Sockets are not recommended, because they add signifi-
cant inductance and parasitic capacitance. If sockets must
be used, consider using zero-profile solderless sockets.
• Use low-inductance and surface-mounted components.
Using all surface-mount components will offer the best
AC performance.
• A resistor (100Ω to 250Ω) in series with the input of the
buffers may help to reduce peaking.
• Plug-in prototype boards and wire-wrap boards will not
function well. A clean layout using RF techniques is
essential—there are no shortcuts.
+5V Pos
BUF600AP
1
In
R_IN
4 ₊₁
160Ω
5
GND
C₂
470nF
C₄
2.2µF
8 ^{ROUT Out}
51Ω
C₁
470nF
C₃
2.2µF
–5V Neg
FIGURE 2. Test Circuit.
IMPEDANCE MATCHING
The BUF600 and BUF601 provide power gain and isolation
between source and load when used as an active tap or
impedance matching device as illustrated in Figure 3. In this
example, there is no output matching path between the
buffer and the 75Ω line. Such matching is not needed when
the distant end of the cable is properly terminated, since
there is no reflected signal when the buffer isolates the
source. This technique allows the full output voltage of the
buffer to be applied to the load.
+5V
470nF
2.2µF
1
V_I
4 _BUF
8
75Ω
160Ω
5
300Ω
470nF
2.2µF
V_O
75Ω
–5V
FIGURE 3. Impedance Converter.
®
BUF600, 601
10