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Analog Devices Inc. AD845KNZ
- Part No.:
- AD845KNZ
- Manufacturer:
- Analog Devices Inc.
- Category:
- Instrumentation, Op Amps, Buffer Amps
- Package:
- 8-DIP (0.300", 7.62mm)
- Datasheet:
-
AD845KNZ.pdf
- Description:
- IC OPAMP JFET 1 CIRCUIT 8DIP
- Quantity:
- Payment:
- Shipping:
Inventory:187
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Product details
Overview
AD845KNZ from Analog Devices is a precision N-channel JFET-input operational amplifier with 16 MHz unity-gain bandwidth, 100 V/µs slew rate, and 350 ns settling time to 0.01%-designed for high-speed, high-accuracy signal conditioning in data acquisition systems. It delivers 0.25 mV max input offset voltage, 94 dB min CMRR, and stable operation driving 100 pF || 500 Ω loads.
For engineers reviewing the AD845KNZ datasheet, AD845KNZ pinout, AD845KNZ application, or AD845KNZ equivalent, key selection criteria include DC precision under dynamic loading, unity-gain stability with capacitive drive capability, low input bias current (≤1 nA), and compatibility with ±15 V supply rails in active filter, photodiode preamp, and ADC buffer circuits.
Technical Context
The AD845KNZ employs complementary bipolar (CB) process technology with laser-wafer trimming to achieve sub-millivolt offset and low drift. Its JFET input stage enables ultra-low input bias current (0.5–1 nA typical) while maintaining high open-loop gain (≥250 V/mV at 500 Ω load) and wide common-mode range (±10.5 V / –13 V).
It is internally compensated for unity-gain stability and specified for operation with 100 pF capacitive load in parallel with 500 Ω resistive load-a critical requirement for driving switched-capacitor ADC inputs and sample-and-hold circuits without oscillation or excessive overshoot.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Unity-Gain Bandwidth | 16 MHz typical - supports stable closed-loop operation up to ~10 MHz in gain-of-1 configurations with minimal phase margin degradation. |
| Slew Rate | 100 V/µs typical - enables full-scale 20 Vp-p output transitions in <200 ns, critical for fast DAC output buffering. |
| Settling Time | 350 ns to 0.01% with 100 pF || 500 Ω load - ensures accurate sampling after multiplexer switching or DAC updates. |
| Input Offset Voltage | 0.25 mV max (K grade) - eliminates need for external nulling in 12-bit systems where 1 LSB = ~2.4 mV at ±10 V full scale. |
| CMRR | 94 dB min over ±10 V input range - maintains accuracy in noisy industrial environments with ground-referenced sensor signals. |
| Input Bias Current | 0.5 nA typical at 25°C - preserves signal integrity in high-impedance photodiode and piezoelectric sensor interfaces. |
| Supply Range | ±4.75 V to ±18 V - allows direct use with standard ±15 V rails and compatibility with legacy hybrid amplifier replacements. |
Pinout & Package
AD845KNZ is housed in an 8-lead plastic mini-DIP (PDIP) package (N-8), compliant with JEDEC MO-095AA. Pin 1 is marked by a notch or dot; pin numbering follows standard DIP convention (counterclockwise from top-left corner).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | Offset Null (to V+) | Connects to +VS for internal offset adjustment; unlike standard op amps, nulling is referenced to positive supply-not ground. |
| 2 | Inverting Input (–IN) | Differential input node; high-impedance JFET gate with 4 pF capacitance and >1011 Ω resistance. |
| 3 | Non-Inverting Input (+IN) | Differential input node; matched to Pin 2 for optimal CMRR and bias current cancellation. |
| 4 | V– (Negative Supply) | Accepts –4.75 V to –18 V; substrate tied to +VS, requiring symmetrical or properly decoupled dual supplies. |
| 5 | NC | No internal connection; electrically isolated and must remain unconnected. |
| 6 | Output | Capable of sourcing/sinking ≥50 mA; specified for linear operation into 500 Ω load with 12.5 V swing. |
| 7 | V+ (Positive Supply) | Accepts +4.75 V to +18 V; substrate connection point; requires low-inductance bypassing per TPC 19. |
| 8 | Offset Null (to V+) | Second null terminal; tied to same +VS node as Pin 1 for balanced trimming. |
Key Features
| Feature | Design Value |
|---|---|
| Unity-gain stable, internally compensated | Eliminates need for external compensation components in gain-of-1 buffers and integrators-reducing BOM count and layout sensitivity. |
| Specified with 100 pF || 500 Ω load | Guarantees 350 ns settling to 0.01% under real-world ADC input conditions, avoiding instability seen with many FET-input op amps. |
| Laser-trimmed input offset & drift | 0.25 mV max offset and 5 µV/°C max drift enable 12-bit accuracy without calibration across 0°C to 70°C (K grade). |
| JFET input with 0.5 nA bias current | Preserves signal fidelity in high-Z sensor interfaces (e.g., photodiodes, pH electrodes) where leakage would otherwise dominate error. |
| 110 dB CMRR at ±10 V common-mode | Rejects power supply noise and ground bounce in mixed-signal PCBs-critical for precision instrumentation front-ends. |
Applications
| Photodiode Preamp | ADC Driver / Buffer |
|---|---|
|
Use Scenario: Amplifying low-current output (pA–nA) from reverse-biased photodiodes in optical sensing and spectrometry. IC Role / Device Role / Timing Role: Transimpedance amplifier with low input bias current and high DC gain to convert photocurrent to measurable voltage. Use Value: 0.5 nA input bias current minimizes dark-current error; 16 MHz bandwidth supports >1 MHz modulation frequencies in lock-in detection. |
Use Scenario: Driving the analog input of successive-approximation ADCs (e.g., AD76xx series) during acquisition phase. IC Role / Device Role / Timing Role: Unity-gain buffer isolating DAC or signal chain from dynamic ADC input capacitance switching. Use Value: 350 ns settling to 0.01% ensures full 16-bit accuracy before conversion starts; 100 V/µs slew prevents slewing-induced distortion. |
| Active Filter (Low-Pass / Band-Pass) | High-Speed Integrator |
|
Use Scenario: Implementing 2nd- to 4th-order active filters in communication channel equalization and anti-aliasing. IC Role / Device Role / Timing Role: Gain block in multiple-feedback or state-variable topologies requiring wide bandwidth and low distortion. Use Value: 16 MHz GBW enables filter cutoffs up to ~2 MHz with <0.1 dB passband ripple; 0.02° differential phase at 4.4 MHz preserves video signal integrity. |
Use Scenario: Precision integration of current pulses in pulse-height analysis and charge measurement circuits. IC Role / Device Role / Timing Role: Integrator core with low input offset and drift to minimize baseline wander over integration windows. Use Value: 0.25 mV max offset contributes <0.05% error over 10 ms integration; 5 µV/°C drift limits thermal drift to <0.35 mV over 70°C ambient range. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar precision high-speed op amp applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| OPA605 | Higher 220 MHz GBW but higher 2.5 nA input bias current; not unity-gain stable without external compensation. | Better for RF gain blocks; less suitable for DC-coupled photodiode preamps or unity-gain ADC buffers. | Select OPA605 only when >50 MHz small-signal bandwidth is required and input impedance >1 GΩ is not critical. |
| LF412CN | Lower 4 MHz GBW, 15 V/µs slew rate, and 5 mV max offset; JFET input but no laser trimming or 100 pF load specification. | Adequate for audio and general-purpose filtering; cannot meet 350 ns settling or 12-bit accuracy requirements. | Choose LF412CN only for cost-sensitive, non-precision applications where speed and offset are secondary. |
Compared with OPA605 and LF412CN, AD845KNZ uniquely balances 16 MHz bandwidth, 100 V/µs slew rate, 0.25 mV offset, and guaranteed 100 pF drive capability-making it the only option among the three qualified for 12-bit data acquisition with sub-400 ns settling and no external compensation.
Availability
AD845KNZ is available at Aetrix Electronics and suitable for active filter design, photodiode signal conditioning, and high-resolution ADC buffering requiring stable component supply across commercial temperature range (0°C to 70°C).
Supply support for AD845KNZ 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
Analog Devices, Inc. is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, headquartered in Norwood, MA.
The AD845 belongs to Analog Devices' precision high-speed op amp product line, engineered specifically to replace hybrid amplifiers in instrumentation, data acquisition, and signal reconstruction systems demanding both DC accuracy and AC performance.
FAQ
What is the operating temperature range for AD845KNZ?
The AD845KNZ is rated for commercial operation from 0°C to +70°C. This grade uses the plastic mini-DIP (N-8) package and is tested across this range for parameters including input offset voltage (0.25 mV max), slew rate (100 V/µs min), and settling time (350 ns to 0.01%). It is not qualified for industrial or extended temperature use-those require AD845AQ or AD845SQ variants in CERDIP packages.
Does AD845KNZ require external compensation for unity-gain stability?
No, AD845KNZ is internally compensated and unity-gain stable. Its compensation network is factory-optimized to maintain phase margin >45° at unity gain, even when driving a 100 pF capacitive load in parallel with 500 Ω. External compensation is unnecessary and may degrade bandwidth or settling performance. The datasheet explicitly confirms this in Product Highlights #3.
How does the offset nulling configuration differ on AD845KNZ compared to standard op amps?
Unlike conventional op amps where offset null pins connect to ±VOS trim potentiometers referenced to ground, AD845KNZ's offset null terminals (Pins 1 and 8) are both connected to the positive supply rail (V+). A 10 kΩ potentiometer is wired between Pins 1 and 8, with its wiper grounded-per Figure 21 in the datasheet. This architecture reflects the internal substrate tie to +VS.
Can AD845KNZ drive a 1000 pF load reliably?
No-AD845KNZ is characterized and guaranteed only for 100 pF || 500 Ω loads. Driving 1000 pF introduces significant phase lag, risking instability, overshoot (>20%), and degraded settling (exceeding 1 µs to 0.01%). For larger capacitive loads, add an isolation resistor (e.g., 50 Ω) between AD845KNZ output and the capacitor, or select a driver with higher current capability like ADA4898-1.
Is AD845KNZ pin-compatible with other AD845 variants like AD845JN or AD845AQ?
Yes-AD845KNZ shares identical pinout and footprint with all AD845 variants (JN, AQ, BQ, SQ) in the same package type. Since AD845KNZ uses the N-8 (plastic DIP) package, it is mechanically and electrically interchangeable with AD845JN. However, AD845AQ uses Q-8 (CERDIP) and is not physically compatible despite identical pin function mapping.
AD845KNZ Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 8-DIP (0.300", 7.62mm)
- Packaging:
- Tube
- Product Status:
- Active
- Amplifier Type:
- J-FET
- Number of Circuits:
- 1
- Output Type:
- -
- Slew Rate:
- 100V/µs
- Gain Bandwidth Product:
- 16 MHz
- -3db Bandwidth:
- -
- Current - Input Bias:
- 500 pA
- Voltage - Input Offset:
- 100 µV
- Current - Supply:
- 10mA
- Current - Output / Channel:
- 50 mA
- Voltage - Supply Span (Min):
- 9.5 V
- Voltage - Supply Span (Max):
- 36 V
- Operating Temperature:
- 0°C ~ 70°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 8-PDIP
AD845KNZ FAQ
1.How can I place an order for AD845KNZ through Aetrix?
Please submit a Request for Quotation (RFQ) for AD845KNZ 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 AD845KNZ reliable?
The price and inventory of AD845KNZ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AD845KNZ is usually 5 days.
3.What payment methods are accepted for AD845KNZ?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AD845KNZ transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AD845KNZ?
AD845KNZ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AD845KNZ 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 AD845KNZ?
For technical support, including AD845KNZ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AD845KNZ requirements.
6.How does Aetrix verify that AD845KNZ is sourced from the original manufacturer or authorized distributors?
All AD845KNZ 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 AD845KNZ meets industry standards.
7.What is the process for return or replacement of AD845KNZ?
All AD845KNZ units undergo pre-shipment inspection (PSI). If there is an issue with AD845KNZ, 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 AD845KNZ part is unused and in its original packaging.
Return procedure for AD845KNZ:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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