Application Hints
(Continued)
should be used from the output of the amplifier to ground
The resistor biases the output into class A operation
The LP124 has improved stability margin for driving capaci-
tive loads No special precautions are needed to drive loads
in the 50 pF to 1000 pF range It should be noted however
that since the power supply current has been reduced by a
factor of 10 so also has the slew rate and gain bandwidth
product This reduction can cause reduced performance in
AC applications where the LM124 is being replaced by an
LP124 Such situations usually occur when the LM124 has
been operated near its power bandwidth
Output short circuits either to ground or to the positive pow-
er supply should be of short time duration Units can be
destroyed not as a result of the short circuit current causing
metal fusing but rather due to the large increase in IC chip
dissipation which will cause eventual failure due to exces-
sive junction temperatures For example If all four amplifi-
ers were simultaneously shorted to ground on a 10V supply
the junction temperature would rise by 110 C
Exceeding the negative common-mode limit on either input
will cause a reversal of phase to the output and force
the amplifier to the corresponding high or low state Exceed-
ing the negative common-mode limit on both inputs will
force the amplifier output to a high state Exceeding the
positive common-mode limit on a single input will not
change the phase of the output However if both inputs
exceed the limit the output of the amplifier will be forced to
a low state In neither case does a latch occur since return-
ing the input within the common mode range puts the input
stage and thus the amplifier in a normal operating mode
The circuits presented in the section on typical applications
emphasize operation on only a single power supply voltage
If complementary power supplies are available all of the
standard op amp circuits can be used In general introduc-
ing a pseudo-ground (a bias voltage reference to V
a
2) will
allow operation above and below this value in single power
supply systems Many application circuits are shown which
take advantage of the wide input common-mode voltage
range which includes ground In most cases input biasing is
not required and input voltages which range to ground can
easily be accommodated
Driving CMOS
Comparator with Hysteresis
TL H 8562 – 3
TL H 8562 – 6
Non-Inverting Amplifier
Adder Subtractor
TL H 8562 – 4
TL H 8562 – 7
Unity Gain Buffer
Positive Integrator
TL H 8562 – 5
TL H 8562 – 8
5
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