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Analog Devices Inc. AD844AQ
- Part No.:
- AD844AQ
- Manufacturer:
- Analog Devices Inc.
- Category:
- Instrumentation, Op Amps, Buffer Amps
- Package:
- 8-CDIP (0.300", 7.62mm)
- Datasheet:
-
AD844AQ.pdf
- Description:
- IC OPAMP CFA 1 CIRCUIT 8CERDIP
- Quantity:
- Payment:
- Shipping:
Inventory:1,232
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Product details
Overview
AD844AQ from Analog Devices is a current-feedback operational amplifier optimized for high-speed current-to-voltage conversion and inverting-mode amplification, delivering 60 MHz bandwidth at gain = −1, 2000 V/μs slew rate, 100 ns settling to 0.1%, and differential phase error of 0.16° at 4.4 MHz - used in flash ADC front-ends and video cable drivers.
For engineers reviewing the AD844AQ datasheet, AD844AQ pinout, AD844AQ application, or AD844AQ equivalent, key selection considerations include its current-feedback architecture (not voltage-feedback), 50 Ω inverting input impedance, ±4.5 V to ±18 V supply range, and CERDIP-8 package thermal performance over −40°C to +85°C.
Technical Context
The AD844AQ employs a junction-isolated complementary bipolar process with a low-impedance inverting input (≈50 Ω) and high-impedance noninverting input (≈10 MΩ), enabling feedback-dominated bandwidth independent of closed-loop gain. Its transresistance is 2.2–3.0 MΩ with 4.5 pF transcapacitance, forming a stable time constant with external RF.
Unlike voltage-feedback op amps, it eliminates classical slew-rate limiting: output dV/dt exceeds 2000 V/μs for full 20 V steps, and settling time remains ~100 ns across gains −1 and −10. It drives 50 Ω loads to ±2.5 V with THD < 0.005% at 100 kHz and supports short-circuit protection up to 80 mA.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Small Signal Bandwidth | 60 MHz at gain = −1 - enables baseband video and fast pulse amplification without gain-bandwidth trade-off |
| Slew Rate | 2000 V/μs - supports clean 20 V step response in ≤100 ns, critical for flash ADC sampling aperture |
| Settling Time | 100 ns to 0.1% (10 V step) - ensures accurate multi-bit digitization within single clock cycle |
| Differential Phase Error | 0.16° at 4.4 MHz - meets broadcast video timing fidelity requirements for composite signal buffering |
| Input Impedance (−IN) | 50 Ω - matches coaxial video/cable driver impedances and simplifies termination design |
| Supply Range | ±4.5 V to ±18 V - allows operation from dual ±5 V logic supplies or ±15 V analog rails |
| Quiescent Current | 6.5 mA - balances speed and power for high-density analog signal chains |
Pinout & Package
AD844AQ is housed in an 8-lead CERDIP (Q) package with hermetic ceramic construction rated for industrial temperature range (−40°C to +85°C). The package features internal substrate connection to +VS and gold-plated leads compatible with standard reflow and wave soldering.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 8 | NULL (Offset Null) | Laser-trimmed offset null terminals - unused in most applications; left open or tied to ±15 V via 10 kΩ for fine adjustment |
| 2 | −IN (Inverting Input) | Low-impedance current-summing node (≈50 Ω) - defines feedback path and bandwidth via RF |
| 3 | +IN (Noninverting Input) | High-impedance voltage-input node (≈10 MΩ) - used only in noninverting configurations; limited to ±1 V transient swing |
| 4 | −VS | Negative supply rail - must be decoupled with ≥0.22 µF ceramic capacitor near pin |
| 5 | TZ (Transimpedance Node) | Internal high-slew node - not user-accessible; determines large-signal response and stability |
| 6 | OUTPUT | Buffered voltage output - capable of ±2.5 V into 50 Ω with <0.005% THD at 100 kHz |
| 7 | +VS | Positive supply rail - substrate tied internally; requires local 0.22 µF ceramic decoupling |
Key Features
| Feature | Design Value |
|---|---|
| Current-feedback architecture | Bandwidth set by feedback resistor, not gain - enables 60 MHz at −1× and 33 MHz at −10× without compensation |
| Zero slew-rate limiting | Rise/fall times independent of output amplitude - 100 ns to 0.1% for both 2 V and 10 V steps |
| Video-optimized linearity | 0.03% differential gain / 0.16° differential phase at 4.4 MHz - preserves color fidelity in RGB or composite video paths |
| Laser-trimmed DC precision | 150 μV max input offset (B grade), 1 μV/°C drift - minimizes baseline error in DC-coupled I-V converters |
| Robust output stage | Short-circuit protected to 80 mA, drives 50 Ω loads - eliminates need for external current-limiting resistors in cable drivers |
Applications
| Flash ADC Front-End | High-Speed DAC Buffer |
|---|---|
Use Scenario: Amplifying analog input to 8–12-bit flash ADC with sub-ns aperture jitter tolerance. IC Role / Device Role / Timing Role: Inverting mode current-to-voltage converter and gain stage - converts DAC current output or conditions sensor signals before sampling. Use Value: 100 ns settling to 0.1% ensures full-scale accuracy across entire conversion window; 2000 V/μs slew prevents missing fast transients during track-and-hold acquisition. |
Use Scenario: Interfacing current-output DACs (e.g., AD97xx series) to terminated 50 Ω transmission lines. IC Role / Device Role / Timing Role: High-speed I-V converter with matched 50 Ω output drive - translates DAC current into clean, low-distortion voltage waveform. Use Value: 50 Ω inverting input impedance eliminates RF-CS pole instability common with voltage-feedback op amps; supports >200 MSPS update rates. |
| Video Cable Driver | Pulse Amplifier |
Use Scenario: Driving 75 Ω coaxial video cables in broadcast equipment or medical imaging displays. IC Role / Device Role / Timing Role: Unity-gain inverting buffer with DC coupling - maintains signal integrity across 0–60 MHz bandwidth including sync pulses and chroma components. Use Value: Differential phase/gain errors of 0.16°/0.03% at 4.4 MHz meet SMPTE 259M and ITU-R BT.601 standards for SD video; drives 100 m cable runs. |
Use Scenario: Amplifying nanosecond-rise-time pulses in laser diode drivers, time-of-flight sensors, or particle detectors. IC Role / Device Role / Timing Role: Fast inverting pulse amplifier with minimal overshoot - shapes and scales TTL/PECL-compatible logic edges. Use Value: Clean 100 ns pulse response with <5% overshoot enables precise timing alignment; 2000 V/μs slew avoids pulse width distortion on 10 V transitions. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar high-speed current-feedback amplifier applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| THS3091DR | Higher slew rate (6500 V/μs), wider bandwidth (200 MHz), but higher quiescent current (11 mA) and no CERDIP packaging | Preferred for >100 MHz pulse amplification; less suitable for space-constrained industrial PCBs requiring hermetic sealing | Select THS3091DR when bandwidth >100 MHz is required and SOIC-8 packaging suffices |
| LMH6720MF | Lower input bias current (1.5 µA vs. 450 nA), similar 600 MHz GBW, but voltage-feedback architecture limits slew rate to 3000 V/μs | Better for high-Z sensor interfaces; lacks true current-feedback benefits in I-V conversion stability | Choose LMH6720MF only when ultra-low input bias is critical and feedback resistor values exceed 5 kΩ |
Compared with THS3091DR and LMH6720MF, the AD844AQ provides superior stability with low-value feedback resistors (<1 kΩ), proven CERDIP reliability in harsh environments, and lower power consumption - making it optimal for cost-sensitive, thermally demanding industrial video and data acquisition systems.
Availability
AD844AQ is available at Aetrix Electronics and suitable for flash ADC front-ends, high-speed DAC interfaces, and video cable drivers requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for AD844AQ 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, with design centers worldwide and ISO 9001-certified manufacturing.
The AD844AQ belongs to Analog Devices' legacy high-speed current-feedback op amp family, engineered specifically for applications demanding wide bandwidth, fast settling, and precision DC performance in instrumentation, video, and data conversion systems.
FAQ
What is the maximum operating temperature range for the AD844AQ?
The AD844AQ is specified for the industrial temperature range of −40°C to +85°C and packaged in an 8-lead CERDIP (Q) housing with hermetic sealing. This rating is confirmed in the Rev. G datasheet under "Ordering Guide" and "Absolute Maximum Ratings," where storage temperature is listed as −65°C to +150°C for the Q package. Operation beyond +85°C risks parametric shift in offset voltage and bandwidth.
Can the AD844AQ be used in noninverting configuration?
Yes, the AD844AQ can be used in noninverting mode, but with strict limitations: gain should be ≥10, input transients must stay below ±1 V, and bandwidth drops significantly below 30 MHz at low gains. The Rev. G datasheet explicitly warns that large-signal behavior degrades at low noninverting gains due to input stage biasing constraints - the AD844AQ is optimized for inverting and I-V converter topologies.
What is the purpose of the TZ pin on the AD844AQ?
The TZ (Transimpedance) pin (Pin 5) is an internal node in the AD844AQ's current-feedback architecture and is not intended for external connection. As described in the "Circuit Description" section (Page 13), TZ is the internal high-slew node where the mirrored input current develops voltage before buffering. It is electrically inaccessible and must remain unconnected - no external components or traces should attach to Pin 5.
How does the AD844AQ differ from a standard voltage-feedback op amp?
The AD844AQ uses current-feedback topology: its inverting input presents ≈50 Ω impedance (not high-Z virtual ground), bandwidth depends primarily on feedback resistor value (not gain), and it exhibits no classical slew-rate limitation. Voltage-feedback op amps rely on high-impedance inputs and gain-bandwidth product constraints - the AD844AQ achieves 60 MHz at −1× gain and 2000 V/μs slew where conventional op amps saturate.
Is the AD844AQ pin-compatible with other AD844 grades like AD844J or AD844B?
Yes, all AD844 variants - including AD844AQ, AD844JN, AD844AR, and AD844SQ - share identical 8-lead CERDIP (Q), 8-lead PDIP (N), and 16-lead SOIC (R) pinouts per Figures 1 and 2 of the Rev. G datasheet. Pin functions (e.g., Pin 2 = −IN, Pin 6 = OUTPUT) are identical across grades; only temperature range, offset voltage spec, and packaging differ - no PCB redesign is needed when upgrading from AD844J to AD844AQ.
AD844AQ Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 8-CDIP (0.300", 7.62mm)
- Packaging:
- Tube
- Product Status:
- Active
- Amplifier Type:
- Current Feedback
- Number of Circuits:
- 1
- Output Type:
- -
- Slew Rate:
- 2000V/µs
- Gain Bandwidth Product:
- -
- -3db Bandwidth:
- 60 MHz
- Current - Input Bias:
- 200 pA
- Voltage - Input Offset:
- 50 µV
- Current - Supply:
- 6.5mA
- Current - Output / Channel:
- 80 mA
- Voltage - Supply Span (Min):
- 9 V
- Voltage - Supply Span (Max):
- 36 V
- Operating Temperature:
- -40°C ~ 85°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 8-CERDIP
AD844AQ FAQ
1.How can I place an order for AD844AQ through Aetrix?
Please submit a Request for Quotation (RFQ) for AD844AQ 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 AD844AQ reliable?
The price and inventory of AD844AQ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AD844AQ is usually 5 days.
3.What payment methods are accepted for AD844AQ?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AD844AQ transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AD844AQ?
AD844AQ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AD844AQ 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 AD844AQ?
For technical support, including AD844AQ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AD844AQ requirements.
6.How does Aetrix verify that AD844AQ is sourced from the original manufacturer or authorized distributors?
All AD844AQ 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 AD844AQ meets industry standards.
7.What is the process for return or replacement of AD844AQ?
All AD844AQ units undergo pre-shipment inspection (PSI). If there is an issue with AD844AQ, 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 AD844AQ part is unused and in its original packaging.
Return procedure for AD844AQ:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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