INA121PA - Low-Power FET-Input Instrumentation Amplifier | TI
N.º da peça: INA121PA ✓ AtivoINA121PA Visão geral
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.
Alternativas drop-in para INA121PA — mesmo encapsulamento, compatível pino a pino. Peças de encapsulamento diferente que exigem retrabalho na PCB são excluídas.
Variantes desta série
Modelos da mesma série compatíveis como drop-in com INA121PA (mesmo formato e footprint) — diferindo em Amplifier Type, Gain Range, Input Bias Current, Input Offset Drift, Input Offset Voltage.
INA121P
✅ Drop-In ⚠️ Especificações não verificadasConsulte o preço
Ver ficha técnica →INA121PA Classificações máximas e características elétricas
| Amplifier Type | Instrumentation amplifier |
| Number of Circuits | 1 circuit |
| Input Bias Current | ±4 pA |
| Corrente de repouso | ±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 |
| Encapsulamento | 8-pin plastic DIP |
| Faixa de temperatura de operação | -40°C to +85°C |
| Tipo de montagem | Through-hole |
Guia de Configuração de Pinos do INA121PA 8-pin plastic dip
Configuração de pinos para INA121PA (pacote 8-pin plastic dip). Este componente analógico possui pinos de entrada, saída e alimentação. Consulte o datasheet do fabricante para configurações de offset null, compensação e pino de enable. Ideal para circuitos de condicionamento de sinal e amplificadores.
Nenhum dado detalhado de pinagem disponível para INA121PA.
Consulte a ficha técnica para a configuração completa dos pinos.
Aplicações típicas
INA121PA é adequado para 6 aplicaçãos: 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.
Recomendado
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.
Recomendado
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.
Recomendado
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.
Recomendado
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.
Recomendado
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.
Recomendado
Resumo dos produtos recomendados
Dados de referência de engenharia para INA121PA — comparação, orientação de projeto e informações de conformidade.
Guia de seleção
Comparação com alternativas
| Parâmetro | Este produto | 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 |
Principais diferenciais
- Very low input bias current for high-impedance sensing (vs INA121P)
- Integrated three-op-amp differential gain stage (vs INA121P)
- Strong common-mode rejection for differential measurement (vs INA121P)
Notas de projeto
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.
Informações de conformidade
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.
