LMP7721MA/NOPB - 3fA Bias Precision Op Amp 17MHz | TI
MPN: LMP7721MA/NOPB ✓ نشطLMP7721MA/NOPB نظرة عامة
An operational amplifier (op amp) is a high-gain voltage amplifier with differential inputs and a single-ended output, used throughout analog signal conditioning, filtering, and instrumentation systems. The LMP7721 belongs to the precision amplifier family within linear integrated circuits; its distinguishing attribute, ultra-low input bias current, enables accurate measurement of tiny currents from very high-impedance sources such as electrochemical electrodes and photodiodes, which standard CMOS or bipolar op amps cannot resolve.
Key features include 7.5 nV/√Hz input voltage noise, 84 dB open-loop gain, typical offset voltage of 26 µV, and input impedance of 10^13 Ω. A shutdown mode reduces supply current to 40 µA, supporting battery-operated designs. The device is specified over the extended industrial temperature range of -40°C to +125°C.
Technically, the LMP7721 employs a CMOS input stage with bias-current cancellation to reach femtoampere input currents. Critically, its unique SOIC-8 pinout physically isolates the input pins (2 and 3) from the output (pin 6) and supply pins (4 and 7), preventing PCB leakage currents from corrupting the femtoampere-level input and enabling effective guard-ring routing.
Typical applications include electrochemical sensors (pH, gas, and ion-selective electrodes), photodiode/transimpedance amplifiers, high-impedance buffers, and medical instrumentation such as glucose monitors and blood gas analyzers, where picoampere-level accuracy is mandatory.
When designing with this device, implement guard rings around the input pins and clean, no-clean-free flux PCB practices to fully realize the 3 fA performance; otherwise board leakage, not the amplifier, will dominate input current error.
بدائل مباشرة لـ LMP7721MA/NOPB — نفس الحزمة، متوافق دبوس بدبوس. تُستثنى القطع ذات الحزم المختلفة التي تتطلب تعديل PCB.
الطرازات في هذه السلسلة
طرازات من نفس السلسلة متوافقة تمامًا مع LMP7721MA/NOPB (نفس عامل الشكل والبصمة) — يختلف في Amplifier Type, Package, RoHS Status, Supply Voltage Range.
LMP7721MA/NOPB
✅ بديل مباشر✗ غير متوفر
تواصل لمعرفة السعر
عرض ورقة البيانات ←LMP7721MAX/NOPB
✅ بديل مباشر📋 بديل مرجعي (غير موجود في الكتالوج)
OPA380AID
⚡ نفس الحزمة✗ غير متوفر
$1.85 / وحدة
عرض ورقة البيانات ←LMP8350MA/NOPB-Q1
⚡ نفس الحزمةتواصل لمعرفة السعر
عرض ورقة البيانات ←LMC6001AIN
⚡ نفس الحزمة ⚠️ مواصفات غير مُتحقق منها📋 بديل مرجعي (غير موجود في الكتالوج)
AD549LH
⚡ نفس الحزمة ⚠️ مواصفات غير مُتحقق منها📋 بديل مرجعي (غير موجود في الكتالوج)
LMP7721MA/NOPB الحدود القصوى والخصائص الكهربائية
| Input Bias Current | 3 fA typical (±20 fA max at 25C, ±900 fA max at 85C) |
| Gain Bandwidth Product | 17 MHz |
| Slew Rate | 12.8 V/us |
| Supply Voltage Range | 1.8 V to 5.5 V (single); ±0.9 V to ±2.75 V (dual) |
| نوع الخرج | Rail-to-Rail |
| Input Voltage Noise | 7.5 nV/√Hz |
| Open-Loop Gain | 84 dB |
| Offset Voltage | 26 uV typical |
| Input Impedance | 10^13 ohm |
| Number of Circuits | 1 |
| Quiescent Current (shutdown) | 40 uA |
| درجة حرارة التشغيل | -40C to +125C |
| العلبة | 8-SOIC (0.154 in, 3.90 mm width), isolated pinout |
| نوع التركيب | Surface Mount |
| Amplifier Type | General Purpose / Precision |
| حالة RoHS | Compliant (NOPB = lead-free) |
تكوين أطراف LMP7721MA/NOPB
| دبوس 1 | OUT — Amplifier output (moved to pin 1 in isolated pinout) |
| دبوس 2 | IN+ — Non-inverting input (guarded / isolated) |
| دبوس 3 | IN- — Inverting input (guarded / isolated) |
| دبوس 4 | V- — Negative supply |
| دبوس 5 | SD — Shutdown control |
| دبوس 6 | NC — No connect (isolation spacing) |
| دبوس 7 | V+ — Positive supply |
| دبوس 8 | NC — No connect (isolation spacing) |
التطبيقات النموذجية
LMP7721MA/NOPB مناسب لـ 6 التطبيقs: Electrochemical Sensor Front End, Photodiode / Transimpedance Amplifier, Medical Instrumentation, High-Impedance Buffer, Battery-Powered Portable Instruments, Test and Measurement / Picoammeter Front Ends.
Electrochemical Sensor Front End
The LMP7721's 3 fA input bias current and 10^13 ohm input impedance make it the definitive buffer for pH, dissolved-oxygen, gas, and ion-selective electrodes, which present gigaohm source impedances. Even picoampere-level bias from ordinary CMOS op amps polarizes electrodes and corrupts readings; the LMP7721 keeps this error orders of magnitude below sensor resolution. Placed directly at the electrode as a unity-gain buffer, its rail-to-rail output swings within millivolts of the 1.8V to 5.5V rail, and its isolated SOIC-8 pinout permits guard rings that suppress board leakage.
موصى به
Photodiode / Transimpedance Amplifier
In picoammeter-grade photodiode receivers, the transimpedance amplifier's input bias current sets the dark-current noise floor. The LMP7721's 3 fA bias and 17 MHz GBW allow megohm feedback resistors with usable bandwidth, enabling optical power detection down to the femtoampere range in optical power meters, fluorescence detectors, and smoke detectors. The 7.5 nV/√Hz voltage noise supports stable operation with large feedback resistances, while the isolated input pinout permits effective guard rings that keep PCB leakage from masking the photodiode signal.
موصى به
Medical Instrumentation
Glucose monitors, blood gas analyzers, and biochemical sensors rely on measuring nanoampere-to-femtoampere electrochemical currents. The LMP7721's ±20 fA guaranteed limit at 25°C delivers the accuracy these diagnostic front ends demand, while its 1.8V operation suits battery-powered portable medical devices. Low offset voltage of 26 µV preserves resolution at small electrode potentials, and the shutdown mode (40 µA quiescent) extends battery life between charges in wearable and handheld medical instruments.
موصى به
High-Impedance Buffer
Piezoelectric, capacitive, and Pyroelectric sensors require buffers with input bias currents far below the signal current. The LMP7721's 10^13 ohm input impedance and 3 fA bias preserve charge integrity when buffering these sources, and its 17 MHz GBW and 12.8 V/µs slew rate handle fast transient events without slew-induced distortion. The rail-to-rail output maximizes dynamic range on low single-supply rails, and the isolated SOIC-8 pinout enables leakage-controlled layout directly at the sensor connector.
موصى به
Battery-Powered Portable Instruments
Handheld pH meters, environmental gas detectors, and water-quality testers benefit from the LMP7721's wide 1.8V to 5.5V supply range, allowing direct operation from two alkaline cells or one Li-ion cell without a boost converter. The shutdown feature reduces supply current to 40 µA between measurements, and the extended -40°C to +125°C range supports outdoor field instruments. Combined with a low-power MCU, the complete analog front end can operate for months on primary cells.
موصى به
Test and Measurement / Picoammeter Front Ends
Bench picoammeters, electrometers, and semiconductor parametric analyzers demand femtoampere-class input stages. The LMP7721's ±20 fA specified limit makes it suitable as the input electrometer amplifier in such instruments, with 84 dB open-loop gain ensuring linearity in high-gain shunt configurations. Its isolated pinout plus guard-ring layout suppresses leakage that would otherwise dominate femtoampere measurements, and the 17 MHz GBW supports fast current-range switching without long settling tails.
موصى به
ملخص المنتجات الموصى بها
بيانات مرجعية هندسية لـ LMP7721MA/NOPB — المقارنة وإرشادات التصميم ومعلومات الامتثال.
دليل الاختيار
المقارنة مع البدائل
| المعامل | هذا المنتج | LMP7721MA/NOPB-Q1 | LMP7721MAX/NOPB | OPA380AID | LMC6001AIN | AD549LH |
|---|---|---|---|---|---|---|
| Package | 8-SOIC (isolated pinout) | 8-SOIC (isolated pinout) - same | 8-SOIC (isolated pinout) - same | 8-SOIC (standard pinout) | 8-SOIC (standard pinout) | 8-SOIC (standard pinout) |
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Analog Devices |
| Input Bias Current | 3 fA typ (±20 fA max 25C) | 3 fA typ (same die) | 3 fA typ (same die) | pA class | 25 fA typ / 10 pA max | ~60 fA typ |
| Gain Bandwidth Product | 17 MHz | 17 MHz | 17 MHz | 80 MHz (TIA config) | 1.3 MHz | 1 MHz |
| Supply Voltage Range | 1.8 V to 5.5 V | 1.8 V to 5.5 V | 1.8 V to 5.5 V | 2.7 V to 5.5 V | ±2 V to ±18 V | ±5 V to ±18 V |
| Automotive Grade | No | Yes (AEC-Q100) | No | No | No | No |
| Drop-in Compatible | - | Yes - pin-to-pin | Yes - pin-to-pin | No - standard pinout | No - standard pinout | No - standard pinout |
أبرز الفروقات
- Industry's lowest specified input bias current (مقابلLMC6001AIN)
- Leakage-isolated pinout enables guard rings (مقابلOPA380AID)
- Higher bandwidth than legacy electrometer op amps (مقابلAD549LH)
ملاحظات التصميم
To realize the 3 fA input bias specification, route guard rings around input pins 2 and 3, driven by a low-impedance potential equal to the input common-mode voltage (buffer the input with a second amplifier or tie to ground for virtual-ground nodes). Suspend input traces over a ground keep-out, minimize trace length, and avoid vias on input nets. The LMP7721's isolated SOIC-8 pinout provides physical spacing between inputs and output/supply pins specifically to make this layout practical.
PCB contamination is the dominant error source in femtoampere designs: flux residue, fingerprints, and moisture create picoampere-level leakage paths that completely mask the amplifier's 3 fA bias. Use no-clean or fully washable flux with validated cleaning, conformal-coat or pot input areas where possible, and select low-leakage, C0G feedback capacitors in TIA configurations. Never use standard electrolytic or generic MLCCs in the input signal path.
Operate the LMP7721 from a clean, well-decoupled 1.8V to 5.5V rail: place 100 nF ceramic capacitors within 2 mm of pins 4 and 7 plus a 1 uF bulk capacitor nearby. In battery designs, power the amplifier from a low-noise LDO rather than directly from a switching converter to preserve the low noise floor enabled by the 7.5 nV/√Hz input stage.
In high-impedance TIA configurations, compensate the feedback network for the photodiode or electrode capacitance to avoid peaking; the 17 MHz GBW permits larger feedback resistors but increases sensitivity to stray capacitance. Keep feedback resistor leads short and elevated from the board to reduce parasitic capacitance across the resistor.
معلومات الامتثال
NOPB suffix denotes TI No-Pb (lead-free) RoHS-compliant construction. AEC-Q100 qualification is available via LMP7721MA/NOPB-Q1.
