Datasheet AMP02 (Analog Devices) - 10

AMP02 Overvoltage Protection Power Supply Considerations
Instrumentation amplifiers invariably sit at the front end of Achieving the rated performance of precision amplifiers in a instrumentation systems where there is a high probability of practical circuit requires careful attention to external influences. exposure to overloads. Voltage transients, failure of a transducer, For example, supply noise and changes in the nominal voltage or removal of the amplifier power supply while the signal source is directly affect the input offset voltage. A PSR of 80 dB means connected may destroy or degrade the performance of an unpro- that a change of 100 mV on the supply (not an uncommon tected device. A common technique is to place limiting resistors in value) will produce a 10 µV input offset change. Consequently, series with each input, but this adds noise. The AMP02 includes care should be taken in choosing a power unit that has a low internal protection circuitry that limits the input current to ±4 mA output noise level, good line and load regulation, and good for a 60 V differential overload (see Figure 5) with power off, temperature stability. In addition, each power supply should be ±2.5 mA with power on. properly bypassed.
4 TA = 25
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C V POWER OFF S =
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15V 3 2 POWER ON 1 0 GE CURRENT – mA –1 LEAKA –2 –3 –4 –100 –80 –60 –40 –20 0 20 40 60 80 100 DIFFERENTIAL INPUT VOLTAGE
Figure 5. AMP02’s Input Protection Circuitry Limits Input Current During Overvoltage Conditions –10– REV. E Document Outline FEATURES APPLICATIONS FUNCTIONAL BLOCK DIAGRAM GENERAL DESCRIPTION SPECIFICATIONS ELECTRICAL CHARACTERISTICS ABSOLUTE MAXIMUM RATINGS ORDERING GUIDE WAFER TEST LIMITS Typical Performance Characteristics APPLICATIONS INFORMATION Input and Output Offset Voltages Input Bias and Offset Currents Gain Common-Mode Rejection Grounding Sense and Reference Terminals Overvoltage Protection Power Supply Considerations OUTLINE DIMENSIONS Revision History