OPA835IDBVT datasheet(36/63 Pages) TI2

36 / 63 page

Figure 9-11 shows the test circuit used for the audio-frequency performance application.

OPA 835

10 W

100 pF

From AP

+2.5 V

-2.5 V

To AP

OUT

The 100-pF capacitor to ground on the input helped to decouple noise pick up in the lab and improved noise performance.

Figure 9-11. OPA835 Audio Precision Analyzer Test Circuit

9.2.1.1 Design Requirements

Design a low distortion, single-ended input to single-ended output audio amplifier using the OPA835 device. The

2700 series audio analyzer from Audio Precision is the signal source and the measurement system.

Table 9-4. Design Requirements

CONFIGURATION

INPUT

EXCITATION

PERFORMANCE

TARGET

RLOAD

OPA835 Unity Gain Config.

1 KHz Tone Frequency

> 110 dBc SFDR

300 Ω and

100 KΩ

9.2.1.2 Detailed Design Procedure

The OPA835 device is tested in this application in a unity-gain buffer configuration. A buffer configuration is

selected as the configuration maximizes the loop gain of the amplifier configuration. At higher closed-loop gains,

the loop gain of the circuit reduces, which results in degraded harmonic distortion. The relationship between

distortion and closed loop gain at a fixed input frequency can be seen in Figure 7-36 in Section 7.9. The test was

performed under varying output-load conditions using a resistive load of 300 Ω and 100 KΩ. Figure 7-34 shows

the distortion performance of the amplifier versus the output resistive load. Output loading, output swing, and

closed-loop gain play a key role in determining the distortion performance of the amplifier.

Note

The 100-pF capacitor to ground on the input helped to decouple noise pickup in the lab and improved

noise performance.

The Audio Precision was configured as a single-ended output in this application circuit. In applications where a

differential output is available, the OPA835 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

power-supply decoupling capacitor must be placed within two inches of the device and can be shared with other

op amps on the same board. A 0.1-μF decoupling capacitor must be placed as close to the power supply pins as

possible, preferably within 0.1 inch. For 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, from 16 Ω to 32 Ω, amplifier performance could begin to degrade. To drive such heavy loads, both

channels of the OPA2835 device can be paralleled with the outputs isolated with 1-Ω resistors to reduce the

loading effects.

OPA835, OPA2835

SLOS713J – JANUARY 2011 – REVISED MARCH 2021

www.ti.com

Submit Document Feedback

Product Folder Links: OPA835 OPA2835

OPA835IDBVT Datasheet(PDF) 36 Page - Texas Instruments

OPA835IDBVT Datasheet(HTML) 36 Page - Texas Instruments

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63

Datasheet Download

Link URL