INA121UA - FET-Input Low Power INA | SOIC-8 | Texas Instruments
MPN: INA121UA ✓ فعالINA121UA جائزہ
An instrumentation amplifier is a precision differential amplifier that combines high input impedance, high common-mode rejection ratio (CMRR), and user-settable gain, making it ideal for extracting small differential signals riding on large common-mode voltages. Within the signal-chain taxonomy, the INA sits between the transducer/bridge and the analog-to-digital converter (ADC), and is itself a category of analog amplifier IC that subclasses under operational amplifier ICs (op-amp IC). The INA121 specifically targets FET-input applications where source impedance is high or where bias current must be minimized to avoid error and self-heating.
Key features include +/-200 uV maximum input offset voltage, +/-2 uV/degrees C input offset drift, 100 nV/sqrt(Hz) low input noise voltage density, 106 dB minimum CMRR, and a low 450 uA typical quiescent current. The device also integrates input protection that can withstand up to +/-40 V differential or common-mode overvoltages without damage, and an output stage capable of driving 1 kohm loads to within 1.5 V of either supply rail.
Internally, the INA121 uses a precision thin-film resistor network with laser-trimmed matching to deliver 0.001% maximum nonlinearity at G = 100. The FET front-end keeps bias current roughly two orders of magnitude lower than bipolar-input instrumentation amplifiers such as the AD620, which simplifies thermal management of high-impedance sensor sources.
Typical applications include weigh scales and load-cell bridges, ECG/biopotential front-ends, thermocouple and RTD signal conditioning, industrial process controls with 4-20 mA loops, and battery-powered portable instrumentation. The wide supply range allows direct operation from industrial +/-15 V rails as well as low-voltage single-supply configurations down to 4.5 V total.
When designing with the INA121UA, place the gain-setting resistor as close as possible to the RG pins to minimize parasitic capacitance, and provide 0.1 uF ceramic bypass capacitors within 5 mm of each supply pin. For single-supply operation, reference the output to mid-rail (VREF = VS/2) and bias the input common-mode voltage above ground by at least 1 V to preserve linear operation. Compared with monolithic zero-drift alternatives, the INA121 trades chopper-stabilized offset for higher bandwidth and lower quiescent current, making it preferred when AC signal fidelity matters more than nano-volt DC accuracy.
This page synthesizes distributor pricing, same-brand and cross-brand drop-in alternatives, and practical design notes not found on the manufacturer datasheet front page.
کے لیے ڈراپ اِن متبادل INA121UA — یکساں پیکیج، پن سے پن مطابقت پذیر۔ مختلف پیکیج والے پرزے جن کے لیے PCB دوبارہ کام درکار ہو، شامل نہیں ہیں۔
اس سیریز میں مختلف ورژن
اسی سیریز کے ماڈلز جو ڈراپ اِن مطابقت رکھتے ہیں INA121UA (یکساں فارم فیکٹر اور فٹ پرنٹ) — میں مختلف Input Bias Current, Input Offset Drift, Input Offset Voltage, Number of Channels, Package.
INA121U
✅ ڈراپ-اِنقیمت کے لیے رابطہ کریں
ڈیٹا شیٹ دیکھیں →INA121UA/2K5
✅ ڈراپ-اِن📋 حوالہ جاتی متبادل (کیٹلاگ میں نہیں)
INA121U/2K5
✅ ڈراپ-اِن📋 حوالہ جاتی متبادل (کیٹلاگ میں نہیں)
INA129UA
✅ ڈراپ-اِن📋 حوالہ جاتی متبادل (کیٹلاگ میں نہیں)
INA128UA
✅ ڈراپ-اِن📋 حوالہ جاتی متبادل (کیٹلاگ میں نہیں)
INA121UA زیادہ سے زیادہ ریٹنگز اور برقی خصوصیات
| Product Type | Instrumentation Amplifier (FET-input) |
| Number of Channels | 1 |
| Gain Range | 1 V/V to 10,000 V/V (external resistor) |
| Bandwidth (G = 100) | 600 kHz |
| Slew Rate | 0.07 V/us |
| Input Bias Current | ±4 pA (max) |
| Input Offset Voltage | ±200 uV (max) |
| Input Offset Drift | ±2 uV/°C (max) |
| CMRR | 106 dB (min) |
| Nonlinearity (G = 100) | 0.001% (max) |
| کوئیسینٹ کرنٹ | ±450 uA |
| Supply Voltage Range | ±2.25 V to ±18 V (dual) / 4.5 V to 36 V (single) |
| Input Protection | ±40 V differential and common-mode |
| پیکیج | 8-pin SOIC (D) |
| ماؤنٹنگ ٹائپ | Surface Mount |
| RoHS اسٹیٹس | Compliant (per DigiKey product page) |
INA121UA پن کنفیگریشن
| پن 1 | RG — Gain-setting resistor pin (tie to pin 8) |
| پن 2 | IN- — Inverting input |
| پن 3 | IN+ — Non-inverting input |
| پن 4 | V- — Negative supply |
| پن 5 | REF — Reference voltage (output baseline) |
| پن 6 | V+ — Positive supply |
| پن 7 | OUT — Amplifier output |
| پن 8 | RG — Gain-setting resistor pin (tie to pin 1) |
عام استعمالات
INA121UA کے لیے موزوں ہے 6 ایپلیکیشنs: Weigh Scale / Load Cell Bridge Front-End, ECG / Biopotential Front-End, Thermocouple and RTD Signal Conditioning, Photodiode Transimpedance Front-End, Industrial Process Control / 4-20 mA Loop Receiver, Portable / Battery-Powered Instrumentation.
Weigh Scale / Load Cell Bridge Front-End
The INA121UA fits weigh-scale front-ends because its ±4 pA input bias current does not load the 350-1000 ohm strain-gauge bridge, preserving the open-circuit voltage that defines scale accuracy. Combined with 106 dB CMRR and 0.001% nonlinearity at G = 100, the INA121UA extracts microvolt-level bridge imbalance at full-scale loads while rejecting the 50/60 Hz line noise on the bridge common-mode voltage. Place RG to set G = 100-500 V/V for typical 10 mV/V full-scale bridge sensitivity, and drive the INA121 output directly into a 16-24 bit sigma-delta ADC reference input.
تجویز کردہ
ECG / Biopotential Front-End
The INA121UA suits ECG and biopotential front-ends because its FET input eliminates the bias-current-cancellation resistors required by bipolar INAs such as AD620, simplifying the patient-isolation interface. Its 106 dB CMRR rejects 50/60 Hz mains pickup on the body-electrode common-mode voltage, while the 100 nV/sqrt(Hz) input noise keeps the trace baseline clean below 0.5 Hz heart-rate frequencies. Configure gain at 1000 V/V (RG = 40 ohm) to amplify the 1 mV ECG signal to a 1 V ADC range; pair with a right-leg drive op-amp for common-mode feedback.
تجویز کردہ
Thermocouple and RTD Signal Conditioning
The INA121UA is appropriate for thermocouple and RTD conditioning because its ±4 pA input bias prevents self-heating of high-impedance sensors and keeps cold-junction compensation error below 0.1 degree C. With ±200 uV offset and ±2 uV/°C drift, the INA121UA delivers enough DC accuracy for type K, J, and T thermocouples across the -200 to +1200 degrees C industrial range. Use G = 100 V/V (RG = 404 ohm) and a precision reference such as the REF5025 for thermocouple reference-junction compensation; the result is a complete 4-20 mA loop-ready temperature transmitter.
تجویز کردہ
Photodiode Transimpedance Front-End
The INA121UA converts photodiode current to voltage in transimpedance configurations because the FET input draws only ±4 pA, leaving the entire photocurrent signal available to develop across the feedback resistor. At G = 1 (RG open), the input behaves as a unity-gain buffer with 600 kHz bandwidth, sufficient for pulse-oximetry and ambient light sensors. For higher gain transimpedance conversion, operate the INA121 in current-to-voltage mode with an external T-network; the result is a wide-dynamic-range optical front-end with picoamp-level sensitivity.
تجویز کردہ
Industrial Process Control / 4-20 mA Loop Receiver
The INA121UA serves as a 4-20 mA current-loop receiver because its ±18 V supply rating tolerates the 24 V industrial rail plus headroom, and its 106 dB CMRR rejects common-mode noise injected by long cable runs. Set gain at 100 V/V (RG = 404 ohm) with a 250 ohm sense resistor to translate 4-20 mA into a 1-5 V output that feeds an ADC or comparator. The ±40 V input protection guards against field-wiring transients and miswiring, a critical robustness feature for factory-floor installations.
تجویز کردہ
Portable / Battery-Powered Instrumentation
The INA121UA suits battery-powered instruments because its ±450 uA quiescent current is roughly half that of bipolar INAs, extending run-time on 9 V or Li-ion cells. The wide ±2.25 V to ±18 V supply lets the device operate from a single 5 V USB rail as well as dual ±15 V industrial supplies without re-design. Pair the INA121 with a low-power ADC like the ADS1115 for a sub-1 mW precision data-acquisition front-end that fits in a handheld multimeter or wireless sensor node.
تجویز کردہ
تجویز کردہ پروڈکٹس کا خلاصہ
کے لیے انجینئرنگ ریفرنس ڈیٹا INA121UA — موازنہ، ڈیزائن رہنمائی، اور تعمیل کی معلومات۔
انتخاب کی گائیڈ
متبادلات کے ساتھ موازنہ
| پیرامیٹر | یہ پروڈکٹ | INA121U | INA121UA/2K5 | INA121U/2K5 | INA129UA | INA128UA |
|---|---|---|---|---|---|---|
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments |
| Package | SOIC-8 (D) | SOIC-8 (D) - same | SOIC-8 (D) - same | SOIC-8 (D) - same | SOIC-8 (D) - same | SOIC-8 (D) - same |
| Input Stage | FET (JFET) | FET (JFET) - same | FET (JFET) - same | FET (JFET) - same | Bipolar | Bipolar |
| Input Bias Current (max) | ±4 pA | ±4 pA | ±4 pA | ±4 pA | ~25 nA | ~5 nA |
| Bandwidth (G = 100) | 600 kHz | 600 kHz | 600 kHz | 600 kHz | 200 kHz | 200 kHz |
| Input Offset Voltage (max) | ±200 uV | ±200 uV | ±200 uV | ±200 uV | ±50 uV | ±50 uV |
| Quiescent Current (typ) | ±450 uA | ±450 uA | ±450 uA | ±450 uA | ±700 uA | ±700 uA |
| Supply Voltage Range | ±2.25 V to ±18 V | ±2.25 V to ±18 V | ±2.25 V to ±18 V | ±2.25 V to ±18 V | ±2.25 V to ±18 V | ±2.25 V to ±18 V |
| Approx. 1k Price (USD, 2026-10-08) | 4.95 | 4.95 | 4.95 | 4.95 | 3.50 | 4.20 |
اہم امتیازی خصوصیات
- Lowest input bias current in the INA1xx SOIC-8 family (بمقابلہINA129UA)
- Higher small-signal bandwidth at G = 100 (بمقابلہINA128UA)
- Wider supply voltage range (بمقابلہAD620 (Analog Devices))
- Pin-compatible with most TI SOIC-8 INA family members (بمقابلہINA126UA)
ڈیزائن نوٹس
Estimated gain calculation for the INA121UA: with RG open, G = 1; with RG = 40 kohm, G = 2; with RG = 404 ohm, G = 100. Placing RG more than 5 mm from pins 1 and 8 introduces parasitic resistance and capacitance that cause gain error at high gains (>100) and may induce peaking above 100 kHz. Use a tight layout and a 1% metal-film resistor for best DC accuracy. Do not float pin 5 (REF); tie it to mid-rail for dual supply, or to a buffered half-supply for single supply.
Place 0.1 uF ceramic bypass capacitors within 5 mm of pins 4 (V-) and 6 (V+) of the INA121UA, plus a 10 uF tantalum or aluminum bulk cap at the supply entry point. The gain-setting resistor RG (between pins 1 and 8) should be the closest component to the SOIC-8 package and routed with short traces to minimize loop area. Use a single ground plane and route the IN- and IN+ traces as a differential pair with matched length and impedance; avoid running them parallel to noisy digital lines.
The INA121UA input stage tolerates up to ±40 V differential or common-mode overvoltage without damage, per the TI datasheet, but sustained overvoltage increases input bias current and can degrade long-term reliability. For ESD-sensitive end-product applications (e.g., ECG patient-connected), add external TVS diodes such as SMAJ5.0CA at the inputs. Source impedance above 10 Gohm can cause thermal noise and pickup; consider adding a 1 Mohm discharge resistor at each input to define the input impedance in floating applications.
Single-supply operation of the INA121UA requires a mid-rail reference on pin 5 (REF) to bias the output into the ADC input range. Use a low-impedance buffer such as the OPA2333 to drive REF, with a 0.1 uF ceramic local bypass. The INA121UA draws ±450 uA quiescent current typical; for battery-powered applications, gate the supplies with a low-leakage load switch to reduce idle current below 1 uA. The wide ±2.25 V to ±18 V supply range also allows direct connection to a +/-15 V industrial rail without LDO regulation.
تعمیل کی معلومات
RoHS and lead-free compliance per DigiKey product page (272057). Industrial temperature grade; not AEC-Q100 qualified for automotive use.
