OPA228PA - 33MHz Low-Noise Precision Op Amp | Texas Instruments
MPN： OPA228PA ✓ 啟用中OPA228PA 概覽
An operational amplifier, commonly called an op amp, is a high-gain differential amplifier whose closed-loop behavior is controlled by an external feedback network. The OPA228 belongs to the precision operational-amplifier class within the broader voltage-feedback amplifier hierarchy. This category supports measurement, control, analog-signal conversion, filtering, buffering, and reference-current drive where low noise, low offset, and stable gain are more important than rail-to-rail operation.
The headline specifications of the OPA228PA establish its position as a wide-band precision amplifier. Its 33 MHz gain-bandwidth product supports accurate amplification of signals well above audio frequency, while the 3 nV/√Hz input-noise density is valuable when the objective is to preserve small signals rather than merely process large ones. Because the OPA228 is optimized for closed-loop gains of 5 or greater, feedback ratios must be selected with that stability requirement in mind. The 8-pin DIP package also supports conventional through-hole PCB construction and prototype instrumentation.
Technically, the OPA228 is designed for demanding precision analog front ends where both AC and DC performance contribute to the final measurement accuracy. High open-loop gain reduces the fraction of the input represented as error, while low input noise improves the signal-to-noise ratio for small source voltages. Its wide bandwidth can also make high-frequency phase margin a decisive layout consideration. The feedback resistor values, compensation network, source impedance, capacitive loading, and grounding arrangement should therefore be treated as part of the amplifier design rather than added afterward.
Typical uses include precision instrumentation amplifiers, low-level sensor signal conditioning, active analog filters, audio and communications interfaces, laboratory measurement equipment, and feedback-control loops. The part is especially useful when a designer needs wide bandwidth and low noise together but does not require a unity-gain-stable amplifier. In filter and gain blocks, its gain setting must remain within the stable operating region specified by the manufacturer.
The primary design consideration is stability. Use a closed-loop gain of at least 5 unless the application and compensation method are specifically supported by the manufacturer. Place input, feedback, and decoupling connections for short, low-inductance paths, and evaluate capacitive loading at the output. The DIP footprint also makes it practical to prototype a circuit before converting it to a smaller surface-mount package.
This product page combines manufacturer specifications, sourcing information, application guidance, comparison fields, and practical design notes into one engineering-focused reference for evaluating the OPA228PA in precision analog designs.
直接替換替代品，適用於 OPA228PA — 相同封裝，腳位對腳位相容。需重新設計 PCB 的不同封裝零件不列入。
此產品無可直接替換的替代品。
申請替代品OPA228PA 最大額定值與電氣特性
| Product Type | High-precision, low-noise operational amplifier |
| Amplifier Architecture | Single voltage-feedback operational amplifier |
| Number of Circuits | 1 circuit |
| Gain-Bandwidth Product | 33 MHz |
| Input Voltage Noise Density | 3 nV/√Hz |
| Minimum Recommended Closed-Loop Gain | 5 |
| 封裝 | 8-pin DIP |
| 安裝類型 | Through-hole |
OPA228PA 8-pin dip 腳位配置指南
OPA228PA（8-pin dip 封裝）的腳位配置。 此類比元件具有輸入、輸出與電源腳位。偏移歸零、補償與致能腳位配置請參閱製造商資料表。適用於訊號調理與放大器電路。
無詳細腳位定義資料： OPA228PA.
請參閱 資料表 以查看完整腳位配置。
典型應用
OPA228PA 適用於 6 應用s: Precision Sensor Signal Conditioning, Laboratory Instrumentation Amplifier, Active Analog Filter, Audio and Communications Interface, Precision Feedback Control, Low-Level Buffering.
Precision Sensor Signal Conditioning
OPA228PA fits low-level sensor front ends where the signal must be amplified without adding excessive noise. Its 3 nV/√Hz input-noise density limits the amplifier's voltage-noise contribution, while the 33 MHz gain-bandwidth product supports both DC accuracy and wider-band signal detail. The part is intended for closed-loop gains of 5 or greater, making it appropriate for sensor amplifiers with a defined gain stage rather than a unity-gain buffer. The feedback network should set the required closed-loop gain, and source impedance should be considered when balancing offset, bias-current, and noise behavior.
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Laboratory Instrumentation Amplifier
OPA228PA is useful in laboratory instrumentation front ends that combine small differential signals with a relatively high closed-loop gain. The 33 MHz gain-bandwidth product provides useful bandwidth margin in precision gain stages, and the 3 nV/√Hz input noise is suitable for measurements where source voltage is small. Because OPA228PA is optimized for gains of 5 or greater, it fits a gain-of-10 or gain-of-50 input block better than a unity-gain follower. Keep input leads short, use a clean reference ground, and verify that output loading and test-instrument capacitance preserve the intended stability and bandwidth.
推薦
Active Analog Filter
OPA228PA can implement active low-pass or band-pass sections when both precision and bandwidth are important. Its 33 MHz gain-bandwidth product is substantially higher than the frequency range normally required in many precision filters, providing useful closed-loop bandwidth margin, while 3 nV/√Hz noise supports low-level filtering. The minimum recommended closed-loop gain of 5 must be respected in the filter topology. Component tolerances and op-amp finite gain-bandwidth can shift the nominal response, so simulate the complete filter with realistic source and load impedances before manufacturing.
推薦
Audio and Communications Interface
OPA228PA is appropriate for precision audio and communications interfaces that need low noise without giving up bandwidth. Its 3 nV/√Hz input-noise density helps preserve low-level content, and the 33 MHz gain-bandwidth product covers frequencies well beyond the audio band. In communications or line-interface circuits, the OPA228 should be used in a stable gain configuration of at least 5. Output drive, supply headroom, and capacitive loading should be checked against the exact interface standard rather than inferred from nominal bandwidth alone.
推薦
Precision Feedback Control
OPA228PA can support closed-loop control and feedback blocks requiring accurate DC behavior together with useful dynamic bandwidth. Its 33 MHz gain-bandwidth product allows a control loop to respond beyond low-frequency regulation bandwidth, while low input noise reduces disturbance coupled through the amplifier. The OPA228 is optimized for closed-loop gains of 5 or greater, so compensation and loop-gain calculations must account for that restriction. Verify output-current capability, capacitive loading, and phase margin using the final sensor or actuator model.
推薦
Low-Level Buffering
OPA228PA can buffer low-level analog nodes when the surrounding circuit provides a supported closed-loop gain of 5 or greater. Its low input-noise density and 33 MHz gain-bandwidth product make it useful when preserving both small-signal amplitude and higher-frequency content. It is not the general choice for a unity-gain voltage follower because that operating condition falls outside the family's stated gain optimization. In a gain-and-buffer arrangement, inspect the feedback ratio, source impedance, DC output offset, and output-current demand before assigning the device.
推薦
推薦產品摘要
工程參考資料，適用於 OPA228PA — 比較、設計指引及合規資訊。
選型指南
與替代品比較
| 參數 | 本產品 |
|---|---|
| Brand | Texas Instruments |
| Package | 8-pin DIP |
| Amplifier Type | High-precision, low-noise operational amplifier |
| Number of Circuits | 1 circuit |
| Gain-Bandwidth Product | 33 MHz |
| Input Voltage Noise Density | 3 nV/√Hz |
| Minimum Recommended Closed-Loop Gain | 5 |
| Mounting Type | Through-hole |
主要差異化特點
- Wide bandwidth for a precision amplifier (對比OPA227PA)
- Higher closed-loop gain is the intended operating mode (對比OPA227PA)
- Low-noise precision in an 8-pin DIP package (對比OPA227PA)
設計說明
Do not treat OPA228PA as a unity-gain-stable buffer. Texas Instruments identifies the OPA228 family as optimized for closed-loop gains of 5 or greater. Select a unity-gain-stable precision amplifier when the circuit requires a follower, or choose a gain stage that meets the manufacturer's stability requirements. This distinction prevents unexpected oscillation, poor phase margin, and an unusable response at low noise gain.
Place the op amp close to the feedback resistors, input components, and supply decoupling so that high-frequency loop area remains small. Connect input returns directly to the device ground without long shared traces, and place supply bypass capacitance at the power pins. The 33 MHz gain-bandwidth product makes trace inductance and parasitic capacitance more consequential than they would be in a much lower-bandwidth precision amplifier.
Evaluate noise over the actual measurement bandwidth rather than quoting 3 nV/√Hz alone. Input-voltage noise integrated over the signal bandwidth combines with resistor noise, source impedance, input bias-current effects, and output-referred noise from later stages. A practical noise calculation should use the complete source and feedback network because changing the gain also changes the op amp's noise gain and bandwidth.
The 8-pin DIP package is convenient for breadboards and through-hole prototypes but larger than surface-mount alternatives. Maintain adequate spacing around adjacent components for probe access, soldering, and thermal airflow. If the circuit is later converted to a surface-mount package, reassess pin mapping, exposed-pad requirements where applicable, parasitic capacitance, and the component layout rather than treating the package change as purely mechanical.
合規資訊
No specific RoHS, REACH, AEC-Q100, lead-free, halogen-free, or conflict-minerals declaration was identified for the OPA228PA ordering option.
