The OPA836 device is tested in this application in a unity-gain buffer configuration. A buffer configuration is selected for maximum loop gain of the amplifier circuit. At higher closed-loop gains, the loop gain of the circuit reduces, which increases the harmonic distortion. The relationship between distortion and closed-loop gain at a fixed input frequency is shown in Figure 7-36 in Section 7.9. The test was performed under using resistive loads of 300 Ω and 100 KΩ. Figure 7-34 shows the distortion performance of the amplifier versus the resistive load. Output loading, output swing, and closed-loop gain play a key role in determining the distortion performance of the amplifier.

The Audio Precision was configured as a single-ended output in this application circuit. In applications where a differential output is available, the OPA836 device can be configured as a differential-to-single-ended amplifier as shown in Figure 9-4. Power-supply bypassing is critical to reject noise from the power supplies. A 2.2-μF supply decoupling capacitor must be placed within 2 inches of the device and can be shared with other operational amplifiers on the same board. A 0.1-μF supply decoupling capacitor must be placed as close to the supply pins as possible, preferably within 0.1 inch. For a split supply, a capacitor is required for both supplies. A 0.1-µF capacitor placed directly between the supplies is also beneficial for improving system noise performance. If the output load is heavy, such as 16 Ω to 32 Ω, performance of the amplifier could begin to degrade. To drive such heavy loads, both channels of the OPA2836 device can be paralleled with their outputs isolated with 1-Ω resistors to reduce the loading effects.