12
FN7186.8
October 15, 2015
Applications Information
Product Description
The EL5120, EL5220, and EL5420 voltage feedback
amplifiers are fabricated using a high voltage CMOS
process. They exhibit rail-to-rail input and output capability,
they are unity gain stable, and have low power consumption
(500µA per amplifier). These features make the EL5120,
EL5220, and EL5420 ideal for a wide range of general-
purpose applications. Connected in voltage follower mode
and driving a load of 10k and 12pF, the EL5120, EL5220,
and EL5420 have a -3dB bandwidth of 12MHz while
maintaining a 10V/µs slew rate. The EL5120 is a single
amplifier, the EL5220 is a dual amplifier, and the EL5420 is a
quad amplifier.
Operating Voltage, Input, and Output
The EL5120, EL5220, and EL5420 are specified with a
single nominal supply voltage from 5V to 15V or a split
supply with its total range from 5V to 15V. Correct operation
is guaranteed for a supply range of 4.5V to 16.5V. Most
EL5120, EL5220, and EL5420 specifications are stable over
both the full supply range and operating junction
temperature range of -40°C to +125°C. Parameter variations
with operating voltage and/or temperature are shown in the
typical performance curves.
The input common-mode voltage range of the EL5120,
EL5220, and EL5420 extends 500mV beyond the supply
rails. The output swings of the EL5120, EL5220, and
EL5420 typically extend to within 80mV of positive and
negative supply rails with load currents of 5mA. Decreasing
load currents will extend the output voltage range even
closer to the supply rails. Figure 25 shows the input and
output waveforms for the device in the unity-gain
configuration. Operation is from ±5V supply with a 10k load
connected to GND. The input is a 10V
P-P
sinusoid. The
output voltage is approximately 9.985V
P-P
.
FIGURE 25. OPERATION WITH RAIL-TO-RAIL INPUT AND
OUTPUT
Short Circuit Current Limit
The EL5120, EL5220, and EL5420 will limit the short circuit
current to ±120mA if the output is directly shorted to the
positive or the negative supply. If an output is shorted
indefinitely, the power dissipation could easily increase such
that the device may be damaged. Maximum reliability is
maintained if the output continuous current never exceeds
±30mA. This limit is set by the design of the internal metal
interconnects.
Output Phase Reversal
The EL5120, EL5220, and EL5420 are immune to phase
reversal as long as the input voltage is limited from (V
S
-)
-0.5V to (V
S
+) +0.5V. Figure 26 shows a photo of the output
of the device with the input voltage driven beyond the supply
rails. Although the device's output will not change phase, the
input's overvoltage should be avoided. If an input voltage
exceeds supply voltage by more than 0.6V, electrostatic
protection diodes placed in the input stage of the device
begin to conduct and overvoltage damage could occur.
FIGURE 26. OPERATION WITH BEYOND-THE-RAILS INPUT
Power Dissipation
With the high-output drive capability of the EL5120, EL5220,
and EL5420 amplifiers, it is possible to exceed the +125°C
maximum operating junction temperature under certain load
current conditions. Therefore, it is important to calculate the
maximum junction temperature for the application to
determine if load conditions need to be modified for the
amplifier to remain in the safe operating area.
The maximum power dissipation allowed in a package is
determined according to Equation 1:
where:
•T
JMAX
= Maximum junction temperature
•T
AMAX
= Maximum ambient temperature
•
JA
= Thermal resistance of the package
•P
DMAX
= Maximum power dissipation in the package
The maximum power dissipation actually produced by an IC
is the total quiescent supply current times the total power
V
S
= ±5V
T
A
= +25°C
A
V
= 1
V
IN
= 10V
P-P
OUTPUT INPUT
V
S
= ±2.5V
T
A
= +25°C
A
V
= 1
V
IN
= 6V
P-P
1V 100µs
1V
P
DMAX
T
JMAX
T
AMAX
–
JA
---------------------------------------------
=
(EQ. 1)
EL5120, EL5220, EL5420
