OPA141_15 Datasheet, PDF (15/30 Pages) Texas Instruments – Single-Supply, 10MHz, Rail-to-Rail Output,Low-Noise, JFET Amplifier

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PHASE-REVERSAL PROTECTION
The OPA141, OPA2141, and OPA4141 family has
internal phase-reversal protection. Many FET- and
bipolar-input op amps exhibit a phase reversal when
the input is driven beyond its linear common-mode
range. This condition is most often encountered in
noninverting circuits when the input is driven beyond
the specified common-mode voltage range, causing
the output to reverse into the opposite rail. The input
circuitry of the OPA141, OPA2141, and OPA4141
prevents phase reversal with excessive
common-mode voltage; instead, the output limits into
the appropriate rail (see Figure 21).
OUTPUT CURRENT LIMIT
The output current of the OPAx141 series is limited
by internal circuitry to +36mA/–30mA
(sourcing/sinking), to protect the device if the output
is accidentally shorted. This short-circuit current
depends on temperature, as shown in Figure 28.
POWER DISSIPATION AND THERMAL
PROTECTION
The OPAx141 series of op amps are capable of
driving 2kΩ loads with power-supply voltages of up to
±18V over the specified temperature range. In a
single-supply configuration, where the load is
connected to the negative supply voltage, the
minimum load resistance is 2.8kΩ at a supply voltage
of +36V. For lower supply voltages (either
single-supply or symmetrical supplies), a lower load
resistance may be used, as long as the output current
does not exceed 13mA; otherwise, the device
short-circuit current protection circuit may activate.
Internal power dissipation increases when operating
at high supply voltages. Copper leadframe
construction used in the OPA141, OPA2141, and
OPA4141 series devices improves heat dissipation
compared to conventional materials. Printed circuit
board (PCB) layout can also help reduce a possible
increase in junction temperature. Wide copper traces
help dissipate the heat by acting as an additional
heatsink. Temperature rise can be further minimized
by soldering the devices directly to the PCB rather
than using a socket.
OPA141
OPA2141
OPA4141
SBOS510B – MARCH 2010 – REVISED MAY 2010
Although the output current is limited by internal
protection circuitry, accidental shorting of one or more
output channels of a device can result in excessive
heating. For instance, when an output is shorted to
mid-supply, the typical short-circuit current of 36mA
leads to an internal power dissipation of over 600mW
at a supply of ±18V.
In the case of a dual OPA2141 in an MSOP-8
package (thermal resistance q_JA = 180°C/W), such
power dissipation would lead the die temperature to
be 220°C above ambient temperature, when both
channels are shorted. This temperature increase
significantly decreases the operating life of the
device.
In order to prevent excessive heating, the OPAx141
series has an internal thermal shutdown circuit, which
shuts down the device if the die temperature exceeds
approximately +180°C. Once this thermal shutdown
circuit activates, a built-in hysteresis of 15°C ensures
that the die temperature must drop to approximately
+165°C before the device switches on again.
Additional consideration should be given to the
combination of maximum operating voltage,
maximum operating temperature, load, and package
type. Figure 33 and Figure 34 show several practical
considerations when evaluating the OPA2141 (dual
version) and the OPA4141 (quad version).
As an example, the OPA4141 has a maximum total
quiescent current of 12.4mA (3.1mA/channel) over
temperature. The TSSOP-14 package has a typical
thermal resistance of 135°C/W. This parameter
means that because the junction temperature should
not exceed 150°C in order to ensure reliable
operation, either the supply voltage must be reduced,
or the ambient temperature should remain low
enough so that the junction temperature does not
exceed 150°C. This condition is illustrated in
Figure 33 for various package types. Moreover,
resistive loading of the output causes additional
power dissipation and thus self-heating, which also
must be considered when establishing the maximum
supply voltage or operating temperature. To this end,
Figure 34 shows the maximum supply voltage versus
temperature for a worst-case dc load resistance of
2kΩ.
Copyright © 2010, Texas Instruments Incorporated
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