**INA170EA/250 Precision Instrumentation Amplifier: A Comprehensive Guide**
The INA170EA/250 is a high-performance, zero-drift instrumentation amplifier designed for precision signal conditioning applications. With its exceptional accuracy, low noise, and high common-mode rejection ratio (CMRR), it has become a go-to choice for various industries.
Key Features and Benefits
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Zero-Drift Architecture: No offset voltage over temperature, eliminating the need for external calibration.
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Low Noise: Equivalent input noise of 0.9 nV/√Hz at 1 kHz, enabling accurate signal measurements.
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High CMRR: Typ. 110 dB at G = 100, effectively rejecting common-mode signals.
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Wide Gain Range: Gain adjustable from 1 to 1000 (G = 1 to 500 for the /250 version), accommodating a wide range of input signal levels.
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Low Input Bias Current: Typ. 1 pA, minimizing input signal distortion.
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Low Offset Voltage: Typ. 250 μV at G = 100, ensuring accurate measurements.
Applications
The INA170EA/250 finds widespread usage in a diverse range of applications, including:
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Sensing and Measurement: Temperature sensors, pressure gauges, strain gauges, and load cells.
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Instrumentation: Data acquisition systems, precision amplifiers, and medical equipment.
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Industrial Automation: Process control, test and measurement equipment, and vibration analysis.
Technical Specifications
| Characteristic |
Value |
| Gain Range |
1 to 1000 (1 to 500 for INA170EA/250) |
| Input Voltage Range |
±10 V |
| Common-Mode Range |
±250 V |
| CMRR |
Min. 100 dB (typ. 110 dB) |
| Noise (1 kHz) |
0.9 nV/√Hz (typ.) |
| Input Bias Current |
1 pA (typ.) |
| Offset Voltage (G = 100) |
250 μV (typ.) |
Tables
Table 1: INA170EA/250 Pin Configuration
| Pin |
Function |
| 1 |
V- |
| 2 |
V+ |
| 3 |
Ref |
| 4 |
IN+ |
| 5 |
OUT |
| 6 |
IN- |
| 7 |
G |
| 8 |
VCC |
| 9 |
VEE |
Table 2: Gain Setting Resistor Values
| Gain |
RG (kΩ) |
| 1 |
Open |
| 5 |
4.99 |
| 10 |
2.49 |
| 20 |
1.24 |
| 50 |
499 |
| 100 |
249 |
| 200 |
124 |
| 500 |
49.9 |
| 1000 |
24.9 |
Table 3: Absolute Maximum Ratings
| Parameter |
Limit |
| Input Voltage Range |
±25 V |
| Output Voltage Range |
±25 V |
| Input Bias Current |
20 mA |
| Storage Temperature |
-65°C to +150°C |
| Operating Temperature |
-40°C to +125°C |
Stories and Lessons Learned
Story 1: The Mismatched Gain Resistors
In an application where high gain was required, one engineer neglected to use precision resistors for the gain-setting network. As a result, the gain varied significantly from the intended value, leading to inaccurate measurements.
Lesson: Always use precision resistors to ensure accurate gain setting.
Story 2: The Unstable Amplifier
Another engineer forgot to connect the bypass capacitor across the power supply pins of the amplifier. This caused the amplifier to oscillate, rendering it unusable.
Lesson: Always connect the bypass capacitor to stabilize the amplifier and prevent oscillations.
Story 3: The Overlooked Input Protection
In a harsh industrial environment, the input protection diodes of the amplifier were not connected. This resulted in the amplifier being damaged by transient voltage spikes.
Lesson: Always provide adequate input protection to protect the amplifier from overvoltage conditions.
Common Mistakes to Avoid
- Using non-precision resistors for gain setting
- Omitting the bypass capacitor
- Neglecting input protection
- Exceeding the maximum input voltage range
- Shorting the input pins together
- Connecting the output directly to the power supply
FAQs
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What is the purpose of the reference input (Ref)?
- The reference input allows for single-ended input signals to be referenced to a fixed voltage level.
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How do I set the gain of the amplifier?
- The gain is set by connecting an external resistor (RG) between the G pin and VEE. Refer to Table 2 for resistor values.
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What is the CMRR bandwidth?
- The CMRR bandwidth is the frequency range over which the amplifier provides the specified level of CMRR.
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Can I use the amplifier with a single power supply?
- Yes, the amplifier can be configured for single supply operation by connecting VEE to ground.
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What is the offset voltage drift?
- Offset voltage drift is the change in offset voltage over temperature. The INA170EA/250 has a zero-drift architecture, eliminating offset voltage drift.
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How do I protect the amplifier from electrostatic discharge (ESD)?
- Handle the amplifier with care and use proper ESD precautions.
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What is the recommended PCB layout for the amplifier?
- Refer to the datasheet for recommended PCB layout guidelines.
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Is there a companion product for the INA170EA/250?
- Yes, the INA171EA/250 is a lower-noise version with a typ. noise of 0.65 nV/√Hz at 1 kHz.
Conclusion
The INA170EA/250 is a dependable and versatile instrumentation amplifier that offers exceptional precision, low noise, and high CMRR. By understanding its features, specifications, and common pitfalls, engineers can harness its full potential in demanding signal conditioning applications.
Call to Action
Explore the INA170EA/250 datasheet and order samples to experience its precision firsthand. For technical support or further information, contact your local Texas Instruments representative.
