OPA2681: Operational Guide for Dual-Speed Wide-band Current-Feedback Op-Amp with Disable Function

The OPA2681 is a high-performance dual-speed wide-band current-feedback operational amplifier, specifically engineered for applications demanding high gain bandwidth and rapid response. Boasting exceptional bandwidth characteristics and low noise performance, this product finds extensive use in audio equipment, video devices, signal processing and data acquisition systems, among other fields. The OPA2681 is designed to deliver outstanding linear performance and flexible application possibilities, with its "disable" function offering users remarkable flexibility to meet the requirements of diverse application scenarios.

Optimizing Bandwidth by Setting Resistor Values

Current-feedback operational amplifiers like the OPA2681 can maintain an almost constant bandwidth across different signal gain settings by appropriately adjusting external resistor values. As illustrated in the typical performance curves, the small-signal bandwidth only decreases slightly with increasing gain. These curves also indicate that each gain setting corresponds to a change in the feedback resistor. The resistance value on the inverting side of the current-feedback op-amp circuit can be regarded as a frequency response compensation component, while their ratio determines the signal gain.

Inverting Amplifier Operation

As a versatile, wide-band current-feedback operational amplifier, the OPA2681 allows designers to utilize most common op-amp application circuits. For dual-op-amp applications that require considerable flexibility in feedback components (such as integrator, trans-impedance amplifiers, and certain filters), the unity-gain stable voltage-feedback OPA2680 should be considered, as the feedback resistor serves as a compensation component in current-feedback op-amps. Wide-band inverting operations, especially summing applications, are particularly well-suited for the OPA2681.

Output Current and Voltage

The OPA2681 offers unparalleled output voltage and current capabilities among low-cost dual monolithic operational amplifiers. Under no-load conditions at 25°C, the output voltage typically swings to within less than 1V of either supply rail; the guaranteed swing is limited to within 1.2V of either rail. With a 15Ω load (the minimum test load), it is guaranteed to deliver over ±135mA of current.

Driving Capacitive Loads

One of the most demanding yet common load conditions for operational amplifiers is capacitive loading. Typically, capacitive loads are found at the input of A/D converters, including additional external capacitors that may be recommended to enhance A/D linearity. When a capacitive load is directly connected to the output pin, high-speed, high-open-loop gain amplifiers like the OPA2681 are highly susceptible to reduced stability and closed-loop response peaking.