EL5164(2004) データシートの表示（PDF） - Intersil
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EL5164 Datasheet PDF : 12 Pages
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EL5164, EL5165, EL5364
acceptable with the Metal-Film resistors giving slightly less
peaking and bandwidth because of additional series
inductance. Use of sockets, particularly for the SO package,
should be avoided if possible. Sockets add parasitic
inductance and capacitance which will result in additional
peaking and overshoot.
Disable/Power-Down
The EL5164 amplifier can be disabled placing its output in a
high impedance state. When disabled, the amplifier supply
current is reduced to < 150µA. The EL5164 is disabled when
its CE pin is pulled up to within 1V of the positive supply.
Similarly, the amplifier is enabled by floating or pulling its CE
pin to at least 3V below the positive supply. For ±5V supply,
this means that an EL5164 amplifier will be enabled when
CE is 2V or less, and disabled when CE is above 4V.
Although the logic levels are not standard TTL, this choice of
logic voltages allows the EL5164 to be enabled by tying CE
to ground, even in 5V single supply applications. The CE pin
can be driven from CMOS outputs.
Capacitance at the Inverting Input
Any manufacturer’s high-speed voltage- or current-feedback
amplifier can be affected by stray capacitance at the
inverting input. For inverting gains, this parasitic capacitance
has little effect because the inverting input is a virtual
ground, but for non-inverting gains, this capacitance (in
conjunction with the feedback and gain resistors) creates a
pole in the feedback path of the amplifier. This pole, if low
enough in frequency, has the same destabilizing effect as a
zero in the forward open-loop response. The use of large-
value feedback and gain resistors exacerbates the problem
by further lowering the pole frequency (increasing the
possibility of oscillation.)
The EL5164, EL5165, and EL5364 have been optimized
with a TBDΩ feedback resistor. With the high bandwidth of
these amplifiers, these resistor values might cause stability
problems when combined with parasitic capacitance, thus
ground plane is not recommended around the inverting input
pin of the amplifier.
Feedback Resistor Values
The EL5164, EL5165, and EL5364 have been designed and
specified at a gain of +2 with RF approximately 412Ω. This
value of feedback resistor gives 300MHz of -3dB bandwidth
at AV = 2 with 2dB of peaking. With AV = -2, an RF of 300Ω
gives 275MHz of bandwidth with 1dB of peaking. Since the
EL5164, EL5165, and EL5364 are current-feedback
amplifiers, it is also possible to change the value of RF to get
more bandwidth. As seen in the curve of Frequency
Response for Various RF and RG, bandwidth and peaking
can be easily modified by varying the value of the feedback
resistor.
Because the EL5164, EL5165, and EL5364 are current-
feedback amplifiers, their gain-bandwidth product is not a
constant for different closed-loop gains. This feature actually
allows the EL5164, EL5165, and EL5364 to maintain about
the same -3dB bandwidth. As gain is increased, bandwidth
decreases slightly while stability increases. Since the loop
stability is improving with higher closed-loop gains, it
becomes possible to reduce the value of RF below the
specified TBDΩ and still retain stability, resulting in only a
slight loss of bandwidth with increased closed-loop gain.
Supply Voltage Range and Single-Supply
Operation
The EL5164, EL5165, and EL5364 have been designed to
operate with supply voltages having a span of greater than
5V and less than 10V. In practical terms, this means that
they will operate on dual supplies ranging from ±2.5V to ±5V.
With single-supply, the EL5164, EL5165, and EL5364 will
operate from 5V to 10V.
As supply voltages continue to decrease, it becomes
necessary to provide input and output voltage ranges that
can get as close as possible to the supply voltages. The
EL5164, EL5165, and EL5364 have an input range which
extends to within 2V of either supply. So, for example, on
±5V supplies, the EL5164, EL5165, and EL5364 have an
input range which spans ±3V. The output range of the
EL5164, EL5165, and EL5364 is also quite large, extending
to within 1V of the supply rail. On a ±5V supply, the output is
therefore capable of swinging from -4V to +4V. Single-supply
output range is larger because of the increased negative
swing due to the external pull-down resistor to ground.
Video Performance
For good video performance, an amplifier is required to
maintain the same output impedance and the same
frequency response as DC levels are changed at the output.
This is especially difficult when driving a standard video load
of 150Ω, because of the change in output current with DC
level. Previously, good differential gain could only be
achieved by running high idle currents through the output
transistors (to reduce variations in output impedance.)
These currents were typically comparable to the entire
5.5mA supply current of each EL5164, EL5165, and EL5364
amplifiers. Special circuitry has been incorporated in the
EL5164, EL5165, and EL5364 to reduce the variation of
output impedance with current output. This results in dG and
dP specifications of TBD% and TBD°, while driving 150Ω at
a gain of 2.
Video performance has also been measured with a 500Ω
load at a gain of +1. Under these conditions, the EL5164,
EL5165, and EL5364 have dG and dP specifications of
0.01% and 0.01°, respectively.
Output Drive Capability
In spite of their low 5.5mA of supply current, the EL5164,
EL5165, and EL5364 are capable of providing a minimum of
±75mA of output current. With a minimum of ±75mA of
output drive, the EL5164, EL5165, and EL5364 are capable
of driving 50Ω loads to both rails, making it an excellent
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