INA121PA - Low-Power FET-Input Instrumentation Amplifier | TI
MPN： INA121PA ✓ 啟用中INA121PA 概覽
An instrumentation amplifier is a specialized analog amplifier optimized for measuring small differential signals superimposed on larger common-mode voltages. Its internal three-op-amp topology provides high input impedance, differential gain, and common-mode rejection without requiring matched external resistors. The INA121PA adds a FET-input stage whose ±4 pA bias current is particularly useful with sensors, transducers, and laboratory sources whose output impedance is high.
Low power consumption is a central advantage of the INA121 family. Its typical quiescent current is ±450 µA, helping reduce supply demand in battery-operated and portable measurement systems. Input offset voltage is specified at ±200 µV, while input offset drift is ±2 µV/°C. The 106 dB CMR figure suppresses common-mode interference, and the wide ±18 V supply range permits operation with both positive and negative supply rails when the measurement circuit requires bipolar input or output signals.
The device combines a low-noise input stage with a gain range of 1 to 10,000 V/V. The 600 kHz bandwidth supports measurement signals extending from slow process-control quantities through higher-bandwidth sensor and communications signals. A low nonlinearity error of 0.001% is important when preserving amplitude accuracy through a substantial gain range. The internal three-op-amp design also simplifies implementation by integrating the gain-setting resistor network.
Typical uses include bridge-transducer amplification, precision current measurement, laboratory instrumentation, biomedical signal acquisition, industrial sensor interfaces, and low-level differential sensing. The very low bias current makes the amplifier appropriate for photodiode, electrochemical-cell, and other high-output-impedance sources. The negative and positive supply capability is valuable for bipolar sensor outputs and offset signals around ground.
When designing around the INA121PA, verify input and output common-mode limits under the intended supply combination, including unbalanced ±18 V operation. Place the gain-setting resistor directly across the designated pins, maintain short input paths to minimize leakage and noise pickup, and use appropriate supply bypassing near the device. Check the complete operating region because gain, supply voltage, output swing, and input common-mode range are interdependent.
This product overview combines the manufacturer’s core electrical characteristics with practical design guidance, package details, and a drop-in replacement assessment. It also identifies the limits of equivalent parts so engineers can preserve the INA121PA’s ±4 pA bias current, 106 dB CMR, low-power operation, and 8-pin plastic-DIP footprint when qualifying alternatives.
直接替換替代品，適用於 INA121PA — 相同封裝，腳位對腳位相容。需重新設計 PCB 的不同封裝零件不列入。
此系列的變體
與下列產品可直接替換的同系列型號： INA121PA （相同外形與佔位） — 差異在於 Amplifier Type, Gain Range, Input Bias Current, Input Offset Drift, Input Offset Voltage.
INA121PA 最大額定值與電氣特性
| Amplifier Type | Instrumentation amplifier |
| Number of Circuits | 1 circuit |
| Input Bias Current | ±4 pA |
| 靜態電流 | ±450 µA |
| Input Offset Voltage | ±200 µV |
| Input Offset Drift | ±2 µV/°C |
| Input Noise | 100 nV/√Hz |
| Common-Mode Rejection Ratio | 106 dB |
| Supply Voltage Range | ±18 V |
| Gain Range | 1 to 10,000 V/V |
| Gain-Bandwidth Product | 600 kHz |
| Nonlinearity Error | 0.001% |
| Architecture | Three-op-amp |
| 封裝 | 8-pin plastic DIP |
| 工作溫度範圍 | -40°C to +85°C |
| 安裝類型 | Through-hole |
INA121PA 8-pin plastic dip 腳位配置指南
INA121PA（8-pin plastic dip 封裝）的腳位配置。 此類比元件具有輸入、輸出與電源腳位。偏移歸零、補償與致能腳位配置請參閱製造商資料表。適用於訊號調理與放大器電路。
無詳細腳位定義資料： INA121PA.
請參閱 資料表 以查看完整腳位配置。
典型應用
INA121PA 適用於 6 應用s: Bridge Transducer Signal Conditioning, Precision Current Measurement, Biomedical and Electrochemical Sensing, Laboratory Instrumentation, Industrial Sensor Interfaces, Portable Battery-Powered Measurement.
Bridge Transducer Signal Conditioning
The INA121PA fits bridge-based measurements because its 106 dB common-mode rejection attenuates the common-mode voltage present at the input while the differential strain or pressure signal is amplified. Gain can be adjusted from 1 to 10,000 V/V to match transducer sensitivity, and the 600 kHz bandwidth provides useful response for many mechanical and industrial sensors. Its ±4 pA input bias current also limits error with resistive dividers having high source impedance. In a bridge circuit, place the amplifier close to the sensor connections, keep the differential pair symmetric, and verify that bridge excitation and output swing remain inside the selected supply limits.
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Precision Current Measurement
The INA121PA can measure a small differential voltage across a shunt while rejecting supply and ground noise, making it appropriate for precision current sensing. Its ±200 µV input offset specification supports accurate low-level measurements, while ±2 µV/°C offset drift is important when the shunt voltage changes with temperature. The 106 dB CMR helps preserve accuracy when the measurement node rides on a larger signal. Select the gain and external RG resistor for the expected shunt voltage, and ensure output headroom remains sufficient across the complete input-current range.
推薦
Biomedical and Electrochemical Sensing
The INA121PA suits low-level biomedical and electrochemical measurements where electrodes or sensors present very high source impedance. The ±4 pA input bias current minimizes error current relative to microampere-scale biological or electrochemical signals, while the 106 dB CMR helps reject interference common to both sensing electrodes. Gain can be set as high as 10,000 V/V for small detector outputs. Use guarded PCB routing, clean surfaces, and appropriate input protection, and confirm the amplifier’s input common-mode range and output swing remain valid for the electrode bias and signal excursion.
推薦
Laboratory Instrumentation
The INA121PA provides the differential input, selectable gain, and common-mode rejection required by general-purpose laboratory measurement equipment. Its 1 to 10,000 V/V gain range supports a broad set of transducer sensitivities, and the 600 kHz bandwidth allows operation beyond slow dc-only measurements. The internal three-op-amp arrangement simplifies instrument construction by avoiding an exact matched-resistor gain network. For bench instruments, provide stable supply bypassing, use a clean RG connection, and account for the specified 0.001% nonlinearity when choosing the gain range and expected signal amplitude.
推薦
Industrial Sensor Interfaces
The INA121PA is appropriate for industrial sensors whose outputs are differential but share a substantial common-mode voltage relative to ground. Its 106 dB CMR rejects coupled industrial noise, while ±4 pA input bias current protects operation with high-impedance dividers, strain gauges, and passive probes. The -40°C to +85°C industrial temperature specification covers many factory and process environments. Robust designs should also consider input protection, surge paths, grounding, and supply isolation because the amplifier’s input ratings do not replace external transient-protection components.
推薦
Portable Battery-Powered Measurement
The INA121PA’s low ±450 µA quiescent current reduces the power burden of portable measurement systems operating from limited battery energy. Its low input bias current and high common-mode rejection support accurate conditioning of sensors without adding substantial load to high-impedance sources. The device can also operate from split supplies when a bipolar measurement signal is required. Designers should still evaluate total supply current, regulator efficiency, shutdown strategy, and the effect of the configured gain on usable bandwidth rather than considering quiescent current alone when estimating battery life.
推薦
推薦產品摘要
工程參考資料，適用於 INA121PA — 比較、設計指引及合規資訊。
選型指南
與替代品比較
| 參數 | 本產品 | INA121P |
|---|---|---|
| Brand | Texas Instruments | Texas Instruments |
| Package | 8-pin plastic DIP | 8-pin plastic DIP - same footprint |
| Amplifier Type | FET-input instrumentation amplifier | FET-input instrumentation amplifier |
| Input Bias Current | ±4 pA | ±4 pA - same family rating |
| Quiescent Current | ±450 µA | ±450 µA - same family rating |
| Input Offset Voltage | ±200 µV | ±200 µV - same family rating |
| Common-Mode Rejection Ratio | 106 dB | 106 dB - same family rating |
| Gain Range | 1 to 10,000 V/V | 1 to 10,000 V/V - same family rating |
| Gain-Bandwidth Product | 600 kHz | 600 kHz - same family rating |
| Supply Voltage Range | ±18 V | ±18 V - same family rating |
| Nonlinearity Error | 0.001% | 0.001% - same family rating |
| Operating Temperature Range | -40°C to +85°C | -40°C to +85°C - same family rating |
主要差異化特點
- Very low input bias current for high-impedance sensing (對比INA121P)
- Integrated three-op-amp differential gain stage (對比INA121P)
- Strong common-mode rejection for differential measurement (對比INA121P)
設計說明
Keep the two input conductors short, symmetric, and away from switching nodes and high-current paths. For high-impedance sources, use a guarded ground or driven guard where appropriate, clean the PCB surface, and avoid contamination around the input pins. Because the specified input bias current is only ±4 pA, board leakage can become significant relative to the intended sensor current.
Check the input common-mode range, output swing, gain, and supply voltage together before finalizing the circuit. The maximum ±18 V supply capability does not permit every combination of gain and signal amplitude. Likewise, the 600 kHz gain-bandwidth product should not be interpreted as 600 kHz at every gain setting; higher gain reduces usable bandwidth.
Place the RG gain-setting resistor and required bypass capacitors close to their associated device pins. Use a short, direct connection for the RG node because long traces can pick up noise and stray capacitance. Ground the bypass returns directly to the appropriate device ground pins, and follow the manufacturer’s package and layout guidance for the 8-pin plastic-DIP footprint.
Use symmetric input routing to minimize conversion of common-mode noise into differential error. Keep the amplifier away from motor-switching nodes, transformers, and high-current return paths, and decouple supply pins close to the component. If the source is adjacent to an analog front end, control connector and cable return paths rather than relying on CMR alone to reject all interference.
合規資訊
The INA121 is an industrial-temperature instrumentation amplifier, but no specific RoHS, REACH, lead-free, halogen-free, conflict-minerals, or automotive qualification statement is included in the cited product information.
