The OPA2684 provides a new level of performance in low-power, wideband, current-feedback (CFB) amplifiers. This CFBPLUS amplifier is among the first to use an internally closed-loop input buffer stage that enhances performance significantly over earlier low-power CFB amplifiers. While retaining the benefits of very low power operation, this new architecture provides many of the benefits of a more ideal CFB amplifier. The closed-loop input stage buffer gives a very low and linearized impedance path at the inverting input to sense the feedback error current. This improved inverting input impedance retains exceptional bandwidth to much higher gains and improves harmonic distortion over earlier solutions limited by inverting input linearity. Beyond simple high-gain applications, the OPA2684 CFBPLUS amplifier permits the gain setting element to be set with considerable freedom from amplifier bandwidth interaction. This allows frequency response peaking elements to be added, multiple input inverting summing circuits to have greater bandwidth, and low-power line drivers to meet the demanding requirements of studio cameras and broadcast video.
The output capability of the OPA2684 also sets a new mark in performance for low-power, current-feedback amplifiers. Delivering a full ±4Vp-p swing on ±5V supplies, the OPA2684 also has the output current to support > ±3Vp-p into 50 loads. This minimal output headroom requirement is complemented by a similar 1.2V input stage headroom giving exceptional capability for single +5V operation.
The OPA2684’s low 3.4mA supply current is precisely trimmed at +25°C. This trim, along with low shift over temperature and supply voltage, gives a very robust design over a wide range of operating conditions.
