Datasheet

47kW47kW
10kW
Microphone,
Hydrophone
etc.
Thermocouple
Center-tap provides
bias current return.
INA129
INA129
INA129
INA129-EP
SBOS508 –DECEMBER 2009 www.ti.com
Figure 25. Providing an Input Common-Mode Current Path
Input Common-Mode Range
The linear input voltage range of the input circuitry of the INA129 is from approximately 1.4 V below the positive
supply voltage to 1.7 V above the negative supply. As a differential input voltage causes the output voltage
increase, however, the linear input range will be limited by the output voltage swing of amplifiers A1 and A2. So
the linear common-mode input range is related to the output voltage of the complete amplifier. This behavior also
depends on supply voltage (see Figure 5 and Figure 6).
Input-overload can produce an output voltage that appears normal. For example, if an input overload condition
drives both input amplifiers to their positive output swing limit, the difference voltage measured by the output
amplifier will be near zero. The output of A3 will be near 0 V even though both inputs are overloaded.
Low Voltage Operation
The INA129 can be operated on power supplies as low as ±2.25 V. Performance remains excellent with power
supplies ranging from ±2.25 V to ±18 V. Most parameters vary only slightly throughout this supply voltage range.
Operation at very low supply voltage requires careful attention to assure that the input voltages remain within
their linear range. Voltage swing requirements of internal nodes limit the input common-mode range with low
power supply voltage. Figure 5 and Figure 6 show the range of linear operation for ±15 V, ±5 V, and ±2.5 V
supplies.
12 Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated
Product Folder Link(s): INA129-EP