OP250 Datasheet, PDF (11/16 Pages) Analog Devices – CMOS Single-Supply Rail-to-Rail Input/Output Operational Amplifiers

+5V
V_IN
R_X
20
OP250
V_OUT
OP250/OP450
Figure 28. Output Short-Circuit Protection
Power Dissipation
Although the OPx50 family of amplifiers are able to provide
load currents of up to 250 mA, proper attention should be given
to not exceed the maximum junction temperature for the device.
The equation for finding the junction temperature is given as:
T_J = P_DISS × θ _JA +T_A
(3)
Where
T_J = OPx50 junction temperature
P_DISS = OPx50 power dissipation
θ_JA = OPx50 junction-to-ambient thermal resistance of
the package; and
T_A = The ambient temperature of the circuit
In any application, the absolute maximum junction temperature
must be limited to +150°C. If this junction temperature is ex-
ceeded, the device could suffer premature failure. If the output
voltage and output current are in phase, for example, with a
purely resistive load, the power dissipated by the OPx50 can be
found as:
( ) ^PDISS ^{= I}LOAD ^{× V}SY ^−VOUT
(4)
Where I_LOAD = OPx50 output load current
V_SY = OPx50 supply voltage; and
V_OUT = The output voltage
By calculating the power dissipation of the device and using the
thermal resistance value for a given package type, the maximum
allowable ambient temperature for an application can be found
using Equation 3.
Overdrive Recovery
The overdrive, or overload, recovery time of an amplifier is the
time required for the output voltage to return to a rated output
voltage from a saturated condition. This recovery time can be
important in applications where the amplifier must recover
quickly after a large transient event. The circuit in Figure 29
was used to evaluate the recovery time for the OPx50. Figures
30 and 31 show the overload recovery of the OP250 from the
positive and negative rails. It takes approximately 0.5 ms for the
amplifier to recover from output overload.
500mV
1µs
Figure 30. Saturation Recovery from the Positive Rail
500mV
1µs
Figure 31. Saturation Recovery from the Negative Rail
Capacitive Loading
The OPx50 family of amplifiers is well suited to driving capaci-
tive loads. The device will remain stable at unity gain even un-
der heavy capacitive load conditions. However, a capacitive load
does not come without a penalty in bandwidth. Figure 32 shows
a graph of the OPx50 unity-gain bandwidth under various ca-
pacitive loads.
1.0
V_S = 2.5V
R_L = 10k
T_A = +25 C
0.8
0.6
V_IN
؉
؊
1V_P–P
1k⍀
OP250
9k⍀
V_OUT
10k⍀
Figure 29. Overload Recovery Time Test Circuit
0.4
0.2
0
0
1
10
100
1k
CAPACITIVE LOAD – nF
Figure 32. Unity-Gain Bandwidth vs. Capacitive Load
As with any amplifier, an increase in capacitive load will also re-
sult in an increase in overshoot and ringing. To improve the
output response, a series R-C network, known as a snubber, can
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