EL5221 Intersil Corporation, EL5221 Datasheet - Page 11

• Manufacturer Part Number: EL5221
• Description: Buffer, Dual 12MHz, Rail-to-rail Input-output
• Manufacturer: Intersil Corporation

EL5221
Unused Buffers
It is recommended that any unused buffer have the input tied
to the ground plane.
Driving Capacitive Loads
The EL5221 can drive a wide range of capacitive loads. As
load capacitance increases, however, the -3dB bandwidth of
the device will decrease and the peaking increase. The
buffers drive 10pF loads in parallel with 10kΩ with just 1.5dB
of peaking, and 100pF with 6.4dB of peaking. If less peaking
is desired in these applications, a small series resistor
(usually between 5Ω and 50Ω) can be placed in series with
the output. However, this will obviously reduce the gain
slightly. Another method of reducing peaking is to add a
"snubber" circuit at the output. A snubber is a shunt load
consisting of a resistor in series with a capacitor. Values of
150Ω and 10nF are typical. The advantage of a snubber is
that it does not draw any DC load current or reduce the gain
Power Supply Bypassing and Printed Circuit
Board Layout
The EL5221 can provide gain at high frequency. As with any
high frequency device, good printed circuit board layout is
necessary for optimum performance. Ground plane
construction is highly recommended, lead lengths should be
as short as possible, and the power supply pins must be well
bypassed to reduce the risk of oscillation. For normal single
supply operation, where the V
- pin is connected to ground,
S
a 0.1µF ceramic capacitor should be placed from V
+ to pin
S
to V
- pin. A 4.7µF tantalum capacitor should then be
S
connected in parallel, placed in the region of the buffer. One
4.7µF capacitor may be used for multiple devices. This same
capacitor combination should be placed at each supply pin
to ground if split supplies are to be used.
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