AD844SQ - 60MHz 2000V/us Current Feedback Op Amp | Analog Devices
N.º da peça: AD844SQ ✓ Ativo| Qtd. | Preço unitário | Total |
|---|---|---|
| 1 | $28.5 | $28,50 |
| 10 | $25.75 | $257,50 |
| 100 | $22.1 | $2.210,00 |
| 500 | $18.95 | $9.475,00 |
| 1.000 | $16.4 | $16.400,00 |
AD844SQ Visão geral
A current-feedback operational amplifier is a high-speed amplifier topology whose inverting input is a low-impedance emitter node rather than a high-impedance differential pair. This architecture lets the -3 dB bandwidth remain nearly independent of closed-loop gain, contrasting with voltage-feedback op-amps whose gain-bandwidth product is constant. Current-feedback op-amps sit in the broader category of high-speed amplifiers within the operational amplifier / amplifier IC family of analog signal-chain semiconductors. They are preferred when large-signal slew rate, high bandwidth at gain, and low distortion across frequency must coexist in one device. The AD844SQ also integrates a low-noise quad transistor useful for buffering and discrete gain stages.
Key performance highlights include 60 MHz small-signal bandwidth at unity gain, 2000 V/us slew rate enabling fast large-signal response, and excellent dc precision. The AD844SQ's "S" grade indicates the standard military operating temperature range, and the "Q" suffix indicates the CERDIP package with screened processing. The 8-pin CERDIP (TO-99-equivalent) form factor is hermetic and qualified for harsh-environment and MIL-grade applications.
Architecturally, the AD844SQ's current-mirror front end combined with a complementary-bipolar output stage lets the part drive heavy loads while maintaining low distortion. The on-board low-noise NPN/PNP quartet enables the AD844 to operate as an extremely low-noise, high-gain building block when wired as a discrete transistor front end, broadening the device's utility beyond a single op-amp function.
Typical uses are RGB/composite video gain stages and cable drivers, high-speed instrumentation front ends, ADC input buffers, IF and baseband signal conditioning, ATE pin electronics, and high-impedance wideband buffers. The wide bandwidth and high slew rate also suit pulse amplifiers, waveform generators, and active filters.
When designing with the AD844SQ, pay attention to feedback resistor selection: the datasheet recommends a specific Rfb value (typically around 1 kohm for gain-of-1 bandwidth) to maintain stability. Use a low-inductance ground return and a solid ground plane; current-feedback amplifiers are more sensitive to parasitic inductance than voltage-feedback parts.
This page synthesizes distributor pricing, hermetic-package drop-in equivalents, and practical layout notes not found in the standalone datasheet, giving procurement and design engineers a single reference for sourcing and applying the AD844SQ.
Alternativas drop-in para AD844SQ — mesmo encapsulamento, compatível pino a pino. Peças de encapsulamento diferente que exigem retrabalho na PCB são excluídas.
Variantes desta série
Modelos da mesma série compatíveis como drop-in com AD844SQ (mesmo formato e footprint) — diferindo em Full-Power Bandwidth, Package, RoHS Status, Slew Rate.
Ferramenta de comparação rápida — selecione peças alternativas para comparação lado a lado:
AD844SQ/883B
✅ Drop-In📋 Alternativa de referência (fora do catálogo)
AD844S
✅ Drop-In📋 Alternativa de referência (fora do catálogo)
AD844ANZ
✅ Drop-In📋 Alternativa de referência (fora do catálogo)
AD844JR
✅ Drop-In📋 Alternativa de referência (fora do catálogo)
LT1226
✅ Drop-In📋 Alternativa de referência (fora do catálogo)
AD844SQ Classificações máximas e características elétricas
| Amplifier Type | Current Feedback Operational Amplifier |
| Number of Circuits | 1 |
| Slew Rate | 2000 V/us |
| Small-Signal Bandwidth | 60 MHz (gain = -1) |
| Bandwidth at Gain of -10 | 33 MHz |
| Full-Power Bandwidth | 20 MHz (20 V pk-pk) |
| Differential Gain Error | 0.03% at 4.4 MHz |
| Differential Phase Error | 0.16 degrees at 4.4 MHz |
| Faixa de temperatura de operação | -55C to +125C (military grade) |
| Encapsulamento | 8-Pin CERDIP (Q) |
| Tipo de montagem | Through-Hole |
| Process Technology | Junction-isolated complementary bipolar (CB) |
| Status RoHS | Non-compliant (hermetic CERDIP) |
Configuração de pinos do AD844SQ
| Pino 1 | NC — Not connected (per datasheet) |
| Pino 2 | -IN — Inverting input (low-impedance current-feedback node) |
| Pino 3 | +IN — Non-inverting input (high-impedance) |
| Pino 4 | V- — Negative supply |
| Pino 5 | NC — Not connected (per datasheet) |
| Pino 6 | OUT — Amplifier output |
| Pino 7 | V+ — Positive supply |
| Pino 8 | NC — Not connected (per datasheet) |
Aplicações típicas
AD844SQ é adequado para 6 aplicaçãos: Broadcast Video Gain Stage / Cable Driver, High-Speed ADC Input Buffer, IF / Baseband Signal Conditioning, ATE Pin Electronics / Pulsed Load Driver, High-Impedance Wideband Buffer / Photodiode Front End, Pulse Amplifier / Waveform Generator Output Stage.
Broadcast Video Gain Stage / Cable Driver
The AD844SQ's 60 MHz bandwidth and 2000 V/us slew rate, combined with 0.03% differential gain error and 0.16 degree differential phase at 4.4 MHz (the NTSC subcarrier frequency), make it well suited to RGB/composite video gain stages and 75 ohm cable drivers. The current-feedback topology maintains bandwidth independent of closed-loop gain, so a gain-of-2 video line driver and a gain-of-10 distribution amp share nearly the same -3 dB point. Designers place the AD844SQ between a sync stripper and the output BNC, with Rfb chosen to set gain and a 75 ohm back-terminated output to absorb cable return loss. Compared to a slower op-amp, the AD844SQ preserves chroma amplitude at high APL transitions without visible color shift.
Recomendado
High-Speed ADC Input Buffer
Fast 12-16 bit ADCs in the 20-50 MSPS class require an input buffer that settles within the ADC's acquisition window and does not introduce distortion above the converter's noise floor. The AD844SQ's 2000 V/us slew rate and current-feedback topology let it settle a full-scale transition fast enough for 40-50 MSPS ADCs, while its low dc error preserves the converter's effective bits. Designers typically use the AD844SQ in an inverting or non-inverting buffer between the front-end anti-alias filter and the ADC input, with Rfb sized for unity or modest gain and a small series resistor to isolate ADC kickback. The hermetic CERDIP-8 package also suits MIL/aerospace instrumentation designs where plastic parts are unacceptable.
Recomendado
IF / Baseband Signal Conditioning
The AD844SQ's wide small-signal bandwidth (60 MHz at -1, 33 MHz at -10) and high slew rate make it an excellent IF / baseband amplifier for receivers operating in the 1-30 MHz range, including shortwave, HF radar, and software-defined radio front ends. The current-feedback topology means a 2-stage 30 MHz IF strip can use identical compensation regardless of per-stage gain, simplifying design. Driving an I/Q demodulator or ADC behind the IF strip, the AD844SQ preserves signal envelope and group delay flatness across the IF passband. Designers typically set Rfb per the datasheet gain chart and place the part between the SAW filter and the demodulator.
Recomendado
ATE Pin Electronics / Pulsed Load Driver
Automatic test equipment (ATE) pin electronics require amplifiers that can swing 10-20 V pk-pk into 50 ohm loads with sub-microsecond settling. The AD844SQ's 2000 V/us slew rate and 20 MHz full-power bandwidth at 20 V pk-pk meet these requirements, while the on-board low-noise transistor quartet lets designers build a discrete low-noise pre-driver around the same die. The hermetic CERDIP-8 package qualifies for MIL-STD-883 and aerospace ATE fixtures where vibration and temperature swing preclude plastic op-amps. Designers typically buffer a precision DAC with the AD844SQ to drive the device-under-test (DUT) input pin.
Recomendado
High-Impedance Wideband Buffer / Photodiode Front End
Photodiode transimpedance amplifiers (TIAs) for wideband optical receivers demand low input bias current, low voltage noise, and enough gain-bandwidth to support the photodiode's pulse rise time. The AD844SQ's complementary-bipolar input stage and integrated low-noise NPNP transistors enable a hybrid TIA where the AD844SQ serves as the high-slew-rate output stage after a discrete low-noise FET input. The 60 MHz bandwidth supports multi-MHz pulse streams while the 2000 V/us slew rate preserves pulse edges. Designers pair the AD844SQ with a low-capacitance PIN photodiode and a small feedback network, achieving nanosecond-class rise times at gains of 10-100.
Recomendado
Pulse Amplifier / Waveform Generator Output Stage
Arbitrary waveform generators, function generators, and pulse-pattern drivers require an output stage that slews cleanly to +/-10 V or more without slew-induced distortion. The AD844SQ's 2000 V/us slew rate and current-feedback topology deliver flat gain across a 1 MHz - 30 MHz operating range, suitable for high-fidelity pulse amplification and active filter networks. Compared to a general-purpose op-amp, the AD844SQ's wide large-signal bandwidth avoids the triangular corner on fast pulses. Designers often place the AD844SQ at the output of a DAC-driven waveform generator, with Rfb chosen to flatten frequency response at the desired gain.
Recomendado
Resumo dos produtos recomendados
Dados de referência de engenharia para AD844SQ — comparação, orientação de projeto e informações de conformidade.
Guia de seleção
Comparação com alternativas
| Parâmetro | Este produto | AD844SQ/883B | AD844S | AD844ANZ | AD844JR | LT1226 |
|---|---|---|---|---|---|---|
| Brand | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices (Linear Technology legacy) |
| Package | 8-CERDIP | 8-CERDIP - same | 8-CERDIP - same | 8-PDIP - same pin count, different package | 8-SOIC - same pin count, surface-mount | 8-PDIP - same pin count, different package |
| Slew Rate | 2000 V/us | 2000 V/us | 2000 V/us | 2000 V/us | 2000 V/us | 1600 V/us (-20%) |
| Bandwidth at Gain -1 | 60 MHz | 60 MHz | 60 MHz | 60 MHz | 60 MHz | 50 MHz (-17%) |
| Operating Temperature | -55C to +125C (MIL) | -55C to +125C (MIL) | -55C to +125C (MIL/Aero) | -40C to +85C (Industrial) | 0C to +70C (Commercial) | -40C to +85C (Industrial) |
| Hermetic Package | Yes (CERDIP) | Yes (CERDIP) | Yes (CERDIP) | No (PDIP) | No (SOIC) | No (PDIP) |
| RoHS Compliant | No | No | No | Yes (with Z suffix) | No (JR suffix) | Varies by suffix |
| Topology | Current Feedback | Current Feedback | Current Feedback | Current Feedback | Current Feedback | Current Feedback |
Principais diferenciais
- Hermetic MIL-grade CERDIP-8 package for harsh environments (vs AD844JR (SOIC-8))
- Full MIL-STD-883 screening available in the same pinout (vs AD844SQ/883B)
- Higher slew rate than the cross-family LT1226 (vs LT1226)
Notas de projeto
Current-feedback amplifiers are far more sensitive to parasitic inductance at the inverting input than voltage-feedback op-amps. Keep the feedback resistor (Rfb) and the inverting-input trace as short as possible; place Rfb within 5 mm of the -IN pin. Use a solid uninterrupted ground plane directly under the package and a low-impedance V+/V- decoupling network (typically 0.1 uF ceramic in parallel with 10 uF tantalum at each supply pin, placed within 3 mm). Estimated: stray inductance above ~5 nH at the -IN node can degrade the AD844SQ's -3 dB bandwidth by 10-20 MHz.
The AD844SQ operates on dual supplies (typically +/-5 V to +/-15 V) with absolute maximum value; the datasheet states the supply overshoot. Decouple each supply pin with a 0.1 uF X7R ceramic in parallel with a 4.7-10 uF tantalum or low-ESR electrolytic capacitor. Estimated: total quiescent current draw is approximately 7-8 mA per supply at +/-15 V (datasheet value should be confirmed), so a small linear regulator such as the LT3032 is adequate for the analog rail. Do not share the AD844SQ's analog ground return with a switching converter's power ground; use a star-ground topology or ground plane partitioning.
Three pitfalls to avoid with the AD844SQ: (1) Do not assume any Rfb value will work - the AD844's bandwidth and stability depend strongly on Rfb; use the datasheet's recommended value (~1 kohm for unity gain, scaling with desired gain). (2) Do not drive large capacitive loads (>50 pF) directly without a series resistor; the AD844SQ's high slew rate and output stage can cause oscillation into 100+ pF loads. (3) Do not assume SOIC-8 layout will work - the AD844SQ is CERDIP-8 (through-hole), and the AD844JR (SOIC-8) has the same signal pins but NC pin positions differ. Always cross-check the pinout against the latest datasheet before PCB assembly.
Informações de conformidade
CERDIP package contains lead-bearing solder/glass and is NOT RoHS compliant. Choose AD844ANZ or AD844ARZ for RoHS-compliant surface-mount designs. AD844S grade is classified as PRODUCTION Aerospace by Analog Devices; consult ADI for full screening details.
