EL2070C
200MHz Current Feedback Amplifier
Printed Circuit Layout
As with any high frequency device, good PCB layout is
necessary for optimum performance. Ground plane con-
struction is a requirement, as is good power-supply and
Offset Adjust bypassing close to the package. The
inverting input is sensitive to stray capacitance, there-
fore connections at the inverting input should be
minimal, close to the package, and constructed with as
little coupling to the ground plane as possible.
Capacitance at the output node will reduce stability,
eventually resulting in peaking, and finally oscillation if
the capacitance is large enough. The design of the
EL2070C allows a larger capacitive load than compara-
ble products, yet there are occasions when a series
resistor before the capacitance may be needed. Please
refer to the graphs to determine the proper resistor value
needed.
Disable/Enable Operation
The EL2070C has a disable/enable control input at pin 8.
The device is enabled and operates normally when pin 8
is left open or tied to pin 7. When more than 350µA is
pulled from pin 8, the EL2070C is disabled. The output
becomes a high impedance, the inverting input is no
longer driven to the positive input voltage, and the sup-
ply current is reduced by 2/3. To make it easy to use this
feature, there is an internal resistor to limit the current to
a safe level (0.8mA) if pin 8 is grounded.
To draw current out of pin 8 an open-collector TTL out-
put, a 5V CMOS output, or an NPN transistor can be
used.
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ELANTEC [ ELANTEC SEMICONDUCTOR ]
