OPA2156: OPA2156: Full power bandwidth

Hello Tony,

Your calculations are correct for a conventional Op amp design. However, the OPA2156 is less conventional from a slew rate standpoint and there is more to the 40 V/us story.

The OPA2156 is a "slew boosted" Op amp. That means that throughout most of its output large-signal slew range, its slew rate is 40 V/us. The slew boost is a benefit when the output is responding to a step, or other fasting changing edge waveform such as a square wave input. In such cases, the Op amp goes into slew boost when the output is slewing from about 10% to 90% of the output swing range; that range being a function of the applied supply voltages. The net result is the output spends less time slewing than it would if the boost weren't implemented in the design.

Beyond the slew boost range, the slew rate actually decreases. This is done to improve the overshoot and settling behavior of the output. The graph in Figure 16 is based on the lower non-slew boosted, or natural slew rate of the OPA2156. To attain the lowest, non slew rate limited bandwidth the curves in Figure 16 should be applied when a linear response is important. The 250 kHz large signal bandwidth would be applicable for a 5 Vpk output.

Regards, Thomas

Precision Amplifiers Applications Engineering

Thanks for the info!
Regards, Tony