5192ACS 데이터 시트보기 (PDF) - Renesas Electronics
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5192ACS Datasheet PDF : 20 Pages
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EL5192, EL5192A
Applications Information
Product Description
The EL5192 is a current-feedback operational amplifier that
offers a wide -3dB bandwidth of 600MHz and a low supply
current of 6mA per amplifier. The EL5192 works with supply
voltages ranging from a single 5V to 10V and they are also
capable of swinging to within 1V of either supply on the
output. Because of their current-feedback topology, the
EL5192 does not have the normal gain-bandwidth product
associated with voltage-feedback operational amplifiers.
Instead, its -3dB bandwidth to remain relatively constant as
closed-loop gain is increased. This combination of high
bandwidth and low power, together with aggressive pricing
make the EL5192 the ideal choice for many low-power/high-
bandwidth applications such as portable, handheld, or
battery-powered equipment.
For varying bandwidth needs, consider the EL5191 with 1GHz
on a 9mA supply current or the EL5193 with 300MHz on a 4mA
supply current. Versions include single, dual, and triple amp
packages with 5 Ld SOT-23, 16 Ld QSOP, and 8 Ld or 16 Ld
SOIC outlines.
Power Supply Bypassing and Printed Circuit
Board Layout
As with any high frequency device, good printed circuit
board layout is necessary for optimum performance. Low
impedance ground plane construction is essential. Surface
mount components are recommended, but if leaded
components are used, lead lengths should be as short as
possible. The power supply pins must be well bypassed to
reduce the risk of oscillation. The combination of a 4.7µF
tantalum capacitor in parallel with a 0.01µF capacitor has
been shown to work well when placed at each supply pin.
For good AC performance, parasitic capacitance should be
kept to a minimum, especially at the inverting input. (See the
Capacitance at the Inverting Input section) Even when ground
plane construction is used, it should be removed from the area
near the inverting input to minimize any stray capacitance at
that node. Carbon or Metal-Film resistors are acceptable with
the Metal-Film resistors giving slightly less peaking and
bandwidth because of additional series inductance. Use of
sockets, particularly for the SOIC package, should be avoided if
possible. Sockets add parasitic inductance and capacitance
which will result in additional peaking and overshoot.
Disable/Power-Down
The EL5192A amplifier can be disabled placing its output in
a high impedance state. When disabled, the amplifier supply
current is reduced to < 150µA. The EL5192A 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 EL5192A amplifier will be
enabled when CE is 2V or less, and disabled when CE is
FN7181 Rev 3.00
May 16, 2007
above 4V. Although the logic levels are not standard TTL,
this choice of logic voltages allows the EL5192A 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 EL5192 has been optimized with a 375 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 EL5192 has been designed and specified at a gain of +2
with RF approximately 375. This value of feedback resistor
gives 300MHz of -3dB bandwidth at AV=2 with 2dB of
peaking. With AV=-2, an RF of 375 gives 275MHz of
bandwidth with 1dB of peaking. Since the EL5192 is a
current-feedback amplifier, 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 EL5192 is a current-feedback amplifier, its
gain-bandwidth product is not a constant for different closed-
loop gains. This feature actually allows the EL5192 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 375 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 EL5192 has been designed to operate with supply
voltages having a span of greater than 5V and less than 10V.
In practical terms, this means that the EL5192 will operate
on dual supplies ranging from ±2.5V to ±5V. With single-
supply, the EL5192 will operate from 5V to 10V.
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