5164ISZ 데이터 시트보기 (PDF) - Renesas Electronics
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5164ISZ Datasheet PDF : 17 Pages
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EL5164, EL5165, EL5364
Disable/Power-Down
The EL5164 and EL5364 amplifiers can be disabled, placing
their outputs in a high impedance state. When disabled, the
amplifiers supply current reduces to <25µA per amplifier. An
amplifier disables 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 a
±5V supply, this means that an amplifier enables when its CE is
2V or less, and disables when CE is above 4V. Although the logic
levels are not standard TTL, this choice of logic voltages allows
the amplifiers to be enabled by tying CE to ground, even in 5V
single supply applications. The CE pin can be driven from CMOS
outputs.
When the amplifier is disabled, if the positive input is driven
beyond ±2V with respect to the negative input, the device can
become active and output the signal. An input diode clamp
network D1 and D2, as shown in Figure 23, can be used to keep
the device disabled while a large input signal is present.
RG
RF
+5V
-
VIN
D1
D2
CE
+
+5V
VOUT
-5V
FIGURE 23. DISABLED AMPLIFIER
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 are optimized for a 510
feedback resistor at AV = +1. 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 for a gain of +2 with RF approximately 412. This value
of feedback resistor gives 450MHz of -3dB bandwidth at AV = 2
with 1dB of peaking. With AV = -2, an RF of 300 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
curves of “Frequency Response for Various RF”, 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 412 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 are designed to operate with
supply voltages having a span of 5V to 10V. In practical terms,
this means that they will operate on dual supplies ranging from
±2.5V to ±5V. With a 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. 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 must 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 150, 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 3.5mA supply
current of each EL5164, EL5165, and EL5364 amplifier. 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 0.01% and
0.01°, while driving 150 at a gain of 2.
Video performance has also been measured with a 500 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.
FN7389 Rev 9.00
January 30, 2014
Page 10 of 17
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