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Texas Instruments LF398AN/NOPB
- Part No.:
- LF398AN/NOPB
- Manufacturer:
- Texas Instruments
- Category:
- Instrumentation, Op Amps, Buffer Amps
- Package:
- 8-DIP (0.300", 7.62mm)
- Datasheet:
-
LF398AN/NOPB.pdf
- Description:
- IC SAMPL/HOLD 1 CIRCUIT 8DIP
- Quantity:
- Payment:
- Shipping:
Inventory:1,043
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Product details
Overview
LF398AN/NOPB from Texas Instruments is a monolithic BI-FET sample-and-hold IC operating as a unity-gain follower with 0.004% typical DC gain error, 20 µs acquisition time to 0.1% with 0.01 µF hold capacitor, and 1 mV typical hold step - used in precision data acquisition systems requiring stable analog signal capture before ADC conversion.
For engineers reviewing the LF398AN/NOPB datasheet, LF398AN/NOPB pinout, LF398AN/NOPB application, or LF398AN/NOPB equivalent, this page delivers verified electrical specs, PDIP-8 package mapping, functional mode behavior, real-world trade-offs in hold capacitor selection, and validated alternative options for sample-and-hold circuit design.
Technical Context
The LF398AN/NOPB uses a bipolar input stage combined with P-channel JFET output devices to achieve low offset voltage (2–7 mV typ), wide bandwidth, and ultrahigh input impedance (1010 Ω), enabling direct interface with high-impedance sensors without accuracy degradation. Its differential logic interface accepts TTL/CMOS/PMOS with 1.4 V threshold and supports ±5 V to ±18 V dual supplies.
In sample mode, the output tracks the input via active charging/discharging of an external hold capacitor; in hold mode, the input is isolated and the output retains the last sampled value with leakage-limited droop (≤5 mV/min with 1 µF). Input offset is adjustable via a dedicated pin without impacting drift performance.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage Range | ±5 V to ±18 V - supports industrial and test equipment rails without level-shifting. |
| Acquisition Time | 20 µs to 0.1% with 0.01 µF hold capacitor - defines minimum sampling interval in multiplexed DAQ systems. |
| Hold Step | 1 mV typical at 25°C - critical error term affecting DC accuracy during mode transition; inversely proportional to hold capacitance. |
| Input Impedance | 10 GΩ - enables use with high-impedance sources (e.g., piezoelectric sensors, pH electrodes) without loading. |
| Gain Error | 0.004% typical - ensures sub-16-bit linearity in precision measurement paths before digitization. |
| Leakage Current (Hold) | 30–200 pA - determines minimum usable hold time before droop exceeds system resolution requirements. |
| Logic Threshold | 1.4 V differential - ensures robust TTL/CMOS compatibility without external biasing networks. |
Pinout & Package
LF398AN/NOPB is packaged in an 8-pin PDIP (Plastic Dual In-line Package) with body size 9.81 mm × 6.35 mm, designed for through-hole prototyping and legacy industrial PCBs. Thermal resistance RθJA is 48.9°C/W, supporting operation up to +70°C ambient.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| V+ | Positive supply | Accepts +5 V to +18 V; must be decoupled locally to suppress noise coupling into high-impedance analog path. |
| OFFSET ADJUST | DC offset compensation | Connects to wiper of 1-kΩ potentiometer between V+ and ground to null input offset without degrading drift. |
| INPUT | Analog input | High-impedance node (10 GΩ); sensitive to layout-induced leakage and capacitive feedthrough from logic lines. |
| V− | Negative supply | Accepts −5 V to −18 V; requires symmetric decoupling to maintain PSRR >80 dB. |
| OUTPUT | Analog output | Low-impedance buffer (0.5–4 Ω in hold mode); drives ADC inputs or downstream op-amps directly. |
| Ch | Hold capacitor connection | External capacitor node; value trades acquisition speed vs. droop rate and dielectric absorption error. |
| LOGIC REFERENCE | Logic reference input | Differential reference for LOGIC pin; sets common-mode baseline for TTL/CMOS-compatible switching. |
| LOGIC | Sample/Hold control | Pull high relative to LOGIC REFERENCE to sample; pull low to hold - edge-rate ≥1 V/µs required. |
Key Features
| Feature | Design Value |
|---|---|
| BI-FET process architecture | Combines bipolar input stage (low offset, wide bandwidth) with JFET output (low noise, low droop) - avoids MOS instability at elevated temperatures. |
| Unity-gain follower operation | Eliminates need for external gain-setting resistors; preserves signal integrity and simplifies layout in high-resolution systems. |
| Differential logic interface | 1.4 V threshold with ±30 V differential tolerance - allows direct connection to TTL/CMOS without level shifters or pull-ups. |
| No feedthrough in hold mode | Input-to-output isolation maintained even with input signals at supply rails - prevents corruption of held value by fast transients. |
| Adjustable input offset | Single-pin trim using external potentiometer - achieves <10 mV total offset across temperature without calibration firmware. |
Applications
| Ramp Generator with Variable Reset | Integrator with Programmable Reset |
|---|---|
|
Use Scenario: Generating linear voltage ramps whose slope and endpoint are dynamically adjusted in real time for laser scanning or waveform synthesis. IC Role / Device Role / Timing Role: LF398AN/NOPB captures reset-level voltage at precise timing instants and holds it to define integrator reference, enabling programmable ramp termination. Use Value: Enables sub-millisecond reset reconfiguration without DAC latency, leveraging 20 µs acquisition and <1 mV hold step for repeatable endpoint accuracy. |
Use Scenario: Precision analog integration where reset level must be set independently of integration time - e.g., charge amplifiers in radiation detection. IC Role / Device Role / Timing Role: LF398AN/NOPB samples and holds a user-defined reference voltage applied to integrator summing junction, isolating reset action from integration cycle. Use Value: Achieves <0.01% gain stability over temperature via 0.004% gain error and 10 GΩ input impedance, eliminating drift-induced baseline walk. |
| Synchronous Correlator | DC and AC Zeroing Circuit |
|
Use Scenario: Extracting weak periodic signals buried in noise by multiplying input with a synchronous reference and integrating result - used in lock-in amplifiers. IC Role / Device Role / Timing Role: LF398AN/NOPB freezes the multiplier output at zero-crossing points of reference signal to enable accurate phase-sensitive sampling. Use Value: Low 1 mV hold step and high feedthrough attenuation (>80 dB at 1 kHz) prevent reference-phase leakage from corrupting correlation amplitude. |
Use Scenario: Nulling sensor offsets in high-gain instrumentation (e.g., strain gauge bridges, thermopile amplifiers) under both static and dynamic conditions. IC Role / Device Role / Timing Role: LF398AN/NOPB implements DC zeroing via OFFSET ADJUST pin and AC zeroing via hold-step cancellation using inverted logic-coupled capacitor network. Use Value: Simultaneous correction of DC offset (<10 mV) and AC hold-step error (±4 mV adjustable) improves effective resolution by ≥1 LSB in 16-bit systems. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar sample-and-hold applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LF398N | Same silicon, no lead-free (Pb) exemption - RoHS non-compliant; identical electrical specs and PDIP-8 footprint. | Not suitable for new designs targeting RoHS compliance; otherwise drop-in replacement in legacy assemblies. | Select LF398N only for repair or backward-compatible manufacturing where Pb-free is not mandated. |
| AD585JN | Higher acquisition speed (1.5 µs), lower hold step (0.25 mV), but requires ±15 V only and has different pinout (16-pin DIP). | Better for high-speed sampling (>100 kSPS), but demands PCB redesign and tighter supply regulation. | Choose AD585JN when acquisition time dominates system performance and board revision is feasible. |
Compared with LF398AN/NOPB, LF398N offers identical performance without RoHS compliance, while AD585JN delivers superior speed and hold fidelity at the cost of pinout incompatibility and stricter supply constraints - making LF398AN/NOPB optimal for cost-sensitive, RoHS-required, medium-speed DAQ upgrades.
Availability
LF398AN/NOPB is available at Aetrix Electronics and suitable for precision data acquisition, industrial process monitoring, and test equipment calibration requiring stable component supply across extended product lifecycles.
Supply support for LF398AN/NOPB includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.
Manufacturer
Texas Instruments is a global semiconductor leader specializing in analog and embedded processing technologies, with decades of heritage in precision linear ICs and industrial-grade components.
The LFx98x family - including LF398AN/NOPB - was engineered for high-accuracy sample-and-hold functions in automated test equipment, medical instrumentation, and aerospace data systems where DC integrity and transient fidelity are non-negotiable.
FAQ
What is the maximum recommended hold capacitor value for LF398AN/NOPB?
The LF398AN/NOPB does not specify an absolute maximum hold capacitor value, but practical limits arise from acquisition time and droop trade-offs. With Ch = 0.01 µF, acquisition time is 20 µs; increasing to 1 µF reduces droop to ≤5 mV/min but extends acquisition to ~200 µs. Capacitors >1 µF risk excessive charging current heating and dielectric absorption errors - polypropylene or NP0 ceramic types are preferred for values >0.1 µF. Always verify settling behavior per Figure 6 in the LF398AN/NOPB datasheet.
Can LF398AN/NOPB operate from a single +15 V supply?
No, the LF398AN/NOPB requires dual-symmetric supplies (e.g., ±5 V to ±18 V) as specified in Absolute Maximum Ratings and Recommended Operating Conditions. Its internal BI-FET architecture relies on balanced positive and negative rails to bias input and output stages correctly. Attempting single-supply operation will result in undefined behavior, output clipping, or permanent damage. For single-supply sample-and-hold applications, consider alternatives like the MAX197 or LTC1098 with rail-to-rail input/output capability.
How does logic signal slew rate affect hold step in LF398AN/NOPB?
LF398AN/NOPB requires logic edge rates ≥1 V/µs at the LOGIC pin to minimize hold step error. Slower edges cause incomplete switching during the aperture window, resulting in increased hold step - potentially exceeding the typical 1 mV spec. This is due to finite charge injection during transition and incomplete isolation of the hold capacitor. TI recommends verifying dV/dt at the pin using a scope; if insufficient, add a small series resistor or buffer (e.g., SN74LVC1G04) to sharpen edges without overshoot. The LF398AN/NOPB datasheet Figure 17 illustrates this dependency.
Is LF398AN/NOPB pin-compatible with LF398A-N or LF398-N variants?
Yes - all LF398x variants (LF398AN/NOPB, LF398A-N, LF398-N) share identical PDIP-8 pinout, terminal functions, and mechanical dimensions. Differences lie solely in tightened electrical specifications (e.g., LF398A-N has lower input offset and hold step), not physical layout. Thus, LF398AN/NOPB can replace LF398-N in existing designs without PCB changes, though performance margins may differ. Always validate against system-level accuracy requirements when substituting.
What is the role of the LOGIC REFERENCE pin in LF398AN/NOPB?
The LOGIC REFERENCE pin establishes the common-mode baseline for the differential LOGIC input pair. It must be tied to a stable reference - typically ground or mid-supply - to define the 1.4 V threshold for logic state recognition. Incorrect referencing (e.g., floating or noisy connection) causes erratic sample/hold transitions and increased hold step. TI specifies that one logic pin must remain ≥2 V below V+ and ≥3 V above V− for reliable operation; thus, LOGIC REFERENCE should be placed within that window, commonly at 0 V for ±15 V supplies. This ensures deterministic mode control in the LF398AN/NOPB.
LF398AN/NOPB Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 8-DIP (0.300", 7.62mm)
- Packaging:
- Tube
- Product Status:
- Active
- Amplifier Type:
- Sample and Hold
- Number of Circuits:
- 1
- Output Type:
- -
- Slew Rate:
- -
- Gain Bandwidth Product:
- -
- -3db Bandwidth:
- -
- Current - Input Bias:
- 10 nA
- Voltage - Input Offset:
- 1 mV
- Current - Supply:
- 4.5mA
- Current - Output / Channel:
- -
- Voltage - Supply Span (Min):
- 10 V
- Voltage - Supply Span (Max):
- 36 V
- Operating Temperature:
- 0°C ~ 70°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 8-PDIP
LF398AN/NOPB FAQ
1.How can I place an order for LF398AN/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LF398AN/NOPB on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for LF398AN/NOPB reliable?
The price and inventory of LF398AN/NOPB are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LF398AN/NOPB is usually 5 days.
3.What payment methods are accepted for LF398AN/NOPB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LF398AN/NOPB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LF398AN/NOPB?
LF398AN/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LF398AN/NOPB order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for LF398AN/NOPB?
For technical support, including LF398AN/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LF398AN/NOPB requirements.
6.How does Aetrix verify that LF398AN/NOPB is sourced from the original manufacturer or authorized distributors?
All LF398AN/NOPB products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that LF398AN/NOPB meets industry standards.
7.What is the process for return or replacement of LF398AN/NOPB?
All LF398AN/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LF398AN/NOPB, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The LF398AN/NOPB part is unused and in its original packaging.
Return procedure for LF398AN/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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