Datasheet

LM124-N , LM224-N
LM2902-N , LM324-N
www.ti.com SNOSC16D –MARCH 2000–REVISED JANUARY 2015
8 Application and Implementation
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
8.1 Application Information
The LM124 series of amplifiers is specified for operation from 3 V to 32 V (±1.5 V to ±16 V). Many of the
specifications apply from –40°C to 125°C. Parameters that can exhibit significant variance with regards to
operating voltage or temperature are presented in Typical Characteristics.
8.2 Typical Applications
Figure 15 emphasizes 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, introducing a pseudo-ground (a bias
voltage reference of V
+
/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.
8.2.1 Non-Inverting DC Gain (0 V Input = 0 V Output)
*R not needed due to temperature independent I
IN
Figure 15. Non-Inverting Amplifier with G=100
8.2.1.1 Design Requirements
For this example application, the required signal gain is a non-inverting 100x±5% with a supply voltage of 5 V.
8.2.1.2 Detailed Design Procedure
Using the equation for a non-inverting gain configuration, Av = 1+R2/R1. Setting the R1 to 10 kΩ, R2 is 99 times
larger than R1, which is 990 kΩ. A 1MΩ is more readily available, and provides a gain of 101, which is within the
desired specification.
The gain-frequency characteristic of the amplifier and its feedback network must be such that oscillation does not
occur. To meet this condition, the phase shift through amplifier and feedback network must never exceed 180°
for any frequency where the gain of the amplifier and its feedback network is greater than unity. In practical
applications, the phase shift should not approach 180° since this is the situation of conditional stability. Obviously
the most critical case occurs when the attenuation of the feedback network is zero.
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