LMP7721MA/NOPB-Q1 - 3fA Input Bias Precision Op Amp | Texas Instruments
MPN: LMP7721MA/NOPB-Q1 ✓ Active| Qty | Unit Price | Extended |
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| 1 | $0 | $0.00 |
| 10 | $0 | $0.00 |
| 100 | $0 | $0.00 |
| 500 | $0 | $0.00 |
| 1,000 | $0 | $0.00 |
Drop-in alternatives for LMP7721MA/NOPB-Q1 — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
LMP8350MA/NOPB-Q1
✅ Drop-In✓ In Stock
$2.53 / Unit
View Datasheet →OPA365AID
✅ Drop-In📋 Reference alternative (not in catalog)
OPA356AID
✅ Drop-In📋 Reference alternative (not in catalog)
AD8628ARZ
⚡ Same Package✓ In Stock
$1.49 / Unit
View Datasheet →LMP7721MA/NOPB-Q1 Maximum Ratings & Electrical Characteristics
| Amplifier Type | Precision, General Purpose |
| Number of Channels | 1 |
| Input Bias Current (typ) | 3 fA |
| Input Bias Current Limit at 25C | ±20 fA |
| Input Bias Current Limit at 85C | ±900 fA |
| Gain Bandwidth Product | 17 MHz |
| Slew Rate | 12.8 V/us |
| Supply Voltage Range | 1.8 V to 5.5 V |
| Output Type | Rail-to-Rail |
| Input Type | Rail-to-Rail |
| Package | 8-SOIC (3.90 mm width) |
| Mounting Type | Surface Mount |
| Packaging | Tube |
| Input Bias Cancellation | Patent-pending cancellation circuitry |
| Special Pinout | Inputs isolated from supply/output pins for leakage prevention |
| RoHS Status | Compliant (NOPB = no lead, RoHS) |
LMP7721MA/NOPB-Q1 Pin Configuration
| Pin 1 | TRIM1 — Input pin 1 isolated from supply/output (special leakage-isolating pinout) |
| Pin 2 | IN- — Inverting input |
| Pin 3 | IN+ — Non-inverting input |
| Pin 4 | GND / V- — Negative supply or ground |
| Pin 5 | TRIM2 — Input pin 2 isolated from supply/output |
| Pin 6 | OUT — Rail-to-rail output |
| Pin 7 | V+ — Positive supply, 1.8 V to 5.5 V |
| Pin 8 | NC/ISO — Isolated pin (see datasheet for exact function) |
Safe Operating Area (SOA) & Thermal Characteristics
No official SOA curve available for this component. Always operate within absolute maximum ratings specified in the datasheet. Ensure adequate cooling and derate as needed.
Typical Applications
LMP7721MA/NOPB-Q1 is suitable for 6 applications: Electrochemical Sensor Front End, Photodiode Transimpedance Amplifier, Ionization Chamber Instrumentation, pH and Chemical Probe Buffering, Battery-Operated Portable Instrumentation, Picoammeter and Electrometer Circuits.
Electrochemical Sensor Front End
Electrochemical gas sensors and ion-selective electrodes produce currents in the picoampere range, demanding amplifiers whose input bias current is orders of magnitude lower. The LMP7721's 3 fA typical bias current and ±20 fA limit at 25C ensure the amplifier loads the cell by less than a few percent of the signal current. Its special SOIC-8 pinout isolates inputs from supply and output traces, and paired with guard rings keeps PCB leakage negligible. Operated from a single 1.8V to 5.5V rail with rail-to-rail I/O, it buffers the sensing electrode directly for battery-powered safety and environmental monitors.
Recommended
Photodiode Transimpedance Amplifier
Low-light detection with photodiodes requires a transimpedance amplifier whose input bias current does not mask the photocurrent. With 3 fA typical input bias and 17 MHz GBW, the LMP7721 supports megohm-scale feedback resistors while maintaining useful closed-loop bandwidth, enabling optical power detection down to femtoampere signal levels. The isolated input pinout, combined with a guard ring driven by the amplifier output, minimizes surface leakage across the feedback path. A feedback capacitor of 0.1 pF to 1 pF stabilizes the circuit at high transimpedance gains in optical instruments and flame sensors.
Recommended
Ionization Chamber Instrumentation
Ionization chambers in radiation monitoring and smoke detection generate sub-picoampere currents that only femtoampere-class front ends can measure accurately. The LMP7721's ±20 fA maximum bias at 25C and ±900 fA at 85C guarantee measurement error far below typical chamber currents, while its 12.8 V/us slew rate handles transient events. Configured as a current-to-voltage converter with guard-ring PCB layout, it preserves accuracy even in high-humidity environments. The wide 1.8V to 5.5V supply range allows operation from lithium cells in portable dosimetry and industrial radiation survey instruments.
Recommended
pH and Chemical Probe Buffering
Glass pH electrodes present source impedances of hundreds of megohms, so any input bias current creates a direct DC voltage error. The LMP7721's 3 fA bias current produces only nanovolt-scale error even across 1 GOhm sources, preserving pH accuracy to 0.01 pH. Its rail-to-rail input stage accommodates the electrode's full millivolt-range output near supply rails on single 3.3V or 5V rails, and rail-to-rail output drives downstream ADCs directly. The isolated input pinout plus conformal-coated guard layout keeps leakage stable across cleaning cycles in chemical process monitoring.
Recommended
Battery-Operated Portable Instrumentation
Portable field instruments need precision analog performance from a single lithium cell. The LMP7721 operates from 1.8V to 5.5V and draws low supply current while delivering 17 MHz GBW and 12.8 V/us slew, so a single stage can buffer high-impedance sensors without multiple gain blocks. Rail-to-rail input and output maximize usable signal swing on a 3V coin cell or single Li-ion cell. Its femtoampere bias means sensors are not discharged by the amplifier during storage or duty-cycled operation, extending battery life and calibration intervals in handheld meters and environmental loggers.
Recommended
Picoammeter and Electrometer Circuits
Picoammeter front ends require the lowest possible amplifier input current and careful leakage management. The LMP7721, specified at 3 fA typical bias, enables measurement ranges starting near tens of femtoamperes when used in a feedback ammeter topology with high-value (10 to 100 GOhm) resistors. The dedicated input-isolated pinout allows short, guarded input traces that never run near supply or output copper, which is the dominant leakage source on conventional op amp pinouts. Combined with PTFE standoffs and post-assembly board cleaning, it forms the core of compact laboratory-grade current measurement modules.
Recommended
Recommended Products Summary
Engineering reference data for LMP7721MA/NOPB-Q1 — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | LMP8350MA/NOPB-Q1 | OPA365AID | OPA356AID | AD8628ARZ |
|---|---|---|---|---|---|
| Package | 8-SOIC (3.90 mm) | 8-SOIC - same body | 8-SOIC - same body | 8-SOIC - same body | 8-SOIC - same body, different pinout |
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Analog Devices |
| Input Bias Current (typ) | 3 fA | [DATA_NEEDED] | pA-class | pA-class | pA-class |
| Gain Bandwidth Product | 17 MHz | [DATA_NEEDED] | 50 MHz | 200 MHz | 2.5 MHz |
| Slew Rate | 12.8 V/us | [DATA_NEEDED] | 25 V/us | 360 V/us | 1 V/us |
| Supply Voltage Range | 1.8 V to 5.5 V | [DATA_NEEDED] | 2.5 V to 5.5 V | 2.5 V to 5.5 V | 2.7 V to 6 V |
| Rail-to-Rail I/O | Yes (input and output) | [DATA_NEEDED] | Yes | Yes | Yes |
| Automotive Grade Option | Yes (-Q1) | Yes (-Q1) | Standard | Standard | Standard |
Key Differentiators
- Industry's lowest guaranteed input bias current (vs OPA365AID)
- Leakage-isolating special pinout (vs AD8628ARZ)
- Automotive-grade Q1 variant availability (vs OPA365AID)
Design Notes
Exploit the LMP7721's special SOIC-8 pinout: route the input traces (pins 2, 3) on the inner layer or through guard rings on the top layer, driven by a low-impedance potential matching the input common-mode voltage. Keep inputs physically far from pins 6 (OUT) and 7 (V+), which the isolated pinout is specifically designed to permit. TI documents this technique as the primary method to prevent PCB leakage current from reaching the input pins.
Board contamination dominates femtoampere measurements. No-clean flux residue and moisture can leak picoamperes - hundreds of times the 3 fA typical bias current. Clean the assembly with isopropyl alcohol and bake dry, use conformal coating on the input area, and avoid FR4-only isolation; consider PTFE standoffs for sub-100 fA measurements. Verify achieved performance by measuring offset with inputs shorted through a GOhm resistor.
In transimpedance configurations, stability is set by the feedback capacitor: CF must satisfy CF >= sqrt(Cj/(2*pi*Rf*GBW)) where Cj is the total input capacitance and GBW is 17 MHz. Start with 0.5 pF at 10 MOhm feedback and reduce empirically. High-value resistors (GOhm class) add significant Johnson noise, which often exceeds amplifier noise - size Rf against your resolution target, not just gain.
Compliance Information
NOPB suffix indicates no-Pb (lead-free) RoHS-compliant packaging. Q1 suffix indicates AEC-Q100 automotive qualification per TI naming convention; REACH and halogen-free status not stated in retrieved data.
