EL5156IS Ver la hoja de datos (PDF) - Renesas Electronics
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EL5156IS Datasheet PDF : 17 Pages
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EL5156, EL5157, EL5256, EL5257
EL5156 Product Description
The EL5156, EL5157, EL5256, and EL5257 are wide
bandwidth, single or dual supply, low power and low offset
voltage feedback operational amplifiers. Both amplifiers are
internally compensated for closed loop gain of +1 or greater.
Connected in voltage follower mode and driving a 500 load,
the -3dB bandwidth is about 610MHz. Driving a 150 load and
a gain of 2, the bandwidth is about 180MHz while maintaining a
600V/µs slew rate. The EL5156 and EL5256 are available with
a power-down pin to reduce power to 17µA typically while the
amplifier is disabled.
Input, Output and Supply Voltage Range
The EL5156 and EL5157 families have been designed to
operate with supply voltage from 5V to 12V. That means for
single supply application, the supply voltage is from 5V to 12V.
For split supplies application, the supply voltage is from ±2.5V
to ±5V. The amplifiers have an input common mode voltage
range from 1.5V above the negative supply (VS- pin) to 1.5V
below the positive supply (VS+ pin). If the input signal is
outside the above specified range, it will cause the output
signal to be distorted.
The outputs of the EL5156 and EL5157 families can swing
from -4V to 4V for VS = ±5V. As the load resistance becomes
lower, the output swing is lower. If the load resistor is 500, the
output swing is about -4V at a 4V supply. If the load resistor is
150, the output swing is from -3.5V to 3.5V.
Choice of Feedback Resistor and Gain Bandwidth
Product
For applications that require a gain of +1, no feedback resistor
is required. Just short the output pin to the inverting input pin.
For gains greater than +1, the feedback resistor forms a pole
with the parasitic capacitance at the inverting input. As this
pole becomes smaller, the amplifier's phase margin is reduced.
This causes ringing in the time domain and peaking in the
frequency domain. Therefore, RF can't be very big for optimum
performance. If a large value of RF must be used, a small
capacitor in the few Pico farad range in parallel with RF can
help to reduce the ringing and peaking at the expense of
reducing the bandwidth.
For gain of +1, RF = 0 is optimum. For the gains other than +1,
optimum response is obtained with RF between 500 to 750.
The EL5156 and EL5157 families have a gain bandwidth
product of 210MHz. For gains 5, its bandwidth can be
predicted by Equation 1:
Gain BW = 210MHz
(EQ. 1)
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 150,
because of the change in output current with DC level. The dG
and dP for these families are about 0.006% and 0.04%, while
driving 150 at a gain of 2. Driving high impedance loads
would give a similar or better dG and dP performance.
Driving Capacitive Loads and Cables
The EL5156 and EL5157 families can drive 27pF loads in
parallel with 500 with less than 5dB of peaking at gain of +1.
If less peaking is desired in applications, a small series resistor
(usually between 5 to 50) can be placed in series with the
output to eliminate most peaking. However, this will reduce the
gain slightly. If the gain setting is greater than 1, the gain
resistor RG can then be chosen to make up for any gain loss
which may be created by the additional series resistor at the
output.
When used as a cable driver, double termination is always
recommended for reflection-free performance. For those
applications, a back-termination series resistor at the
amplifier's output will isolate the amplifier from the cable and
allow extensive capacitive drive. However, other applications
may have high capacitive loads without a back-termination
resistor. Again, a small series resistor at the output can help to
reduce peaking.
Disable/Power-Down
The EL5156 and EL5256 can be disabled and their output
placed in a high impedance state. The turn-off time is about
330ns and the turn-on time is about 130ns. When disabled, the
amplifier's supply current is reduced to 17µA typically, thereby
effectively eliminating the power consumption. The amplifier's
power-down can be controlled by standard TTL or CMOS
signal levels at the ENABLE pin. The applied logic signal is
relative to VS- pin. Letting the ENABLE pin float or applying a
signal that is less than 0.8V above VS- will enable the amplifier.
The amplifier will be disabled when the signal at ENABLE pin is
above VS+ - 1.5V.
Output Drive Capability
The EL5156 and EL5157 families do not have internal short
circuit protection circuitry. They have a typical short circuit
current of 95mA and 70mA. If the output is shorted indefinitely,
the power dissipation could easily overheat the die or the
current could eventually compromise metal integrity. Maximum
reliability is maintained if the output current never exceeds
±40mA. This limit is set by the design of the internal metal
interconnect. Note that in transient applications, the part is
robust.
Power Dissipation
With the high output drive capability of the EL5152 and EL5153
families, it is possible to exceed the +125°C absolute
maximum junction temperature under certain load current
conditions. Therefore, it is important to calculate the maximum
junction temperature for an application to determine if load
conditions or package types need to be modified to assure
operation of the amplifier in a safe operating area.
FN7386 Rev 6.00
July 7, 2009
Page 10 of 17
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