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Texas Instruments APA100 manual Changing the Gain

Models: APA100

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3.5 Changing the Gain

Changing the Gain

3.5 Changing the Gain

The APA100 EVM is set with a gain of 31.4 dB, but can be adjusted. The front-end has a gain of 4.4 dB (−1.667 V/V), and a back-end gain of 27 dB (−22.4 V/V), for a total of 31.4 dB (37.3 V/V). The back-end gain needs to be kept constant, because it is set by the control-loop feedback system with the TLV2464A, TPA2001D1, and TAS5111. The front-end gain is set by section A of the quad operational amplifier TLV2464A. The front-end gain is set by Equation 1, which is a ratio of feedback to input resistors.

Front−end Gain + *	R4	(VV)	(1)
	(R5 ) R6)

The APA100 EVM total gain can then be set by multiplying the front-end and back-end gains, as shown in Equation 2.

Total Gain + 22.4	R4	(VV)	(2)
	(R5 ) R6)

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Texas Instruments APA100 manual Changing the Gain

Contents

APA100 Audio Power AmplifiersUser’s Guide AugustProducts IMPORTANT NOTICEApplications About This Manual How to Use This ManualRead This First Information About Cautions and WarningsData Sheets Related Documentation From Texas InstrumentsFCC Warning This is an example of a warning statementContents Figures TablesPage EVM OverviewChapter Topic1.2 Power Requirements 1.1 Features1.2.1Supply Voltage EVM Basic Function/Block Diagram 1.3 EVM Basic Function/Block DiagramEVM Overview Integrator EVM Basic Function/Block DiagramFeedback TLV2464Chapter PCB DesignSchematic Page2.1 PCB Layout 2.1.1Split Ground Plane2.1.3Analog Section Layout 2.1.2H-BridgeLayoutFigure 2−2. APA100 Split Plane Bottom Layout 2.1.4PCB Layers Figure 2−3. Top Copper and SilkscreenPCB Layout Figure 2−4. Bottom Copper and SilkscreenFigure 2−5. Drill Drawing PCB DesignTable 2−1. Parts List 2.2 Bill of MaterialsBill of Materials Schematic 2.3 SchematicPCB Design Page Page EVM OperationChapter Topic3.1 Quick Start Figure 3−1. Quick Start Module Map3.4 Error Signals 3.2 Power−Up/Down Sequence3.3 Reset Button/Mute Table 3−1. TAS5111 Error Decoding3.5 Changing the Gain Page Technical InformationChapter Topic4.1 Feedback System Design Figure 4−1. APA100 Block DiagramPhase Margin + 180 Phase at Fc Figure 4−4. APA100 Integrator Design Closed−loop gain + 1.5 0 C10 V1 1 0 4.2 TPA2001D1 Class-DModulator Ch1: 3V/Div Ch2: 3V/Div Ch3: 3V/Div Ch4: 1V/Div Figure 4−7. TPA2001D1 Block DiagramTPA2001D1 Class-DModulator t − Time −4.4 TLV2464A Gain Setting and Feedback 4.3 TAS5111 H-Bridge4.5 LC Filter Figure 4−9. APA100 Output Filter4.6 Thermal Table 4−1. TAS5111 Thermal TableAs an indication of the importance of keeping the thermal grease layer thin, if the thermal grease layer increases to 0.002 inch thick, the required heatsink thermal resistance changes to 2.4C/W Page Measured ResultsChapter Topic5.1 Total Harmonic Distortion + Noise Total Harmonic Distortion + NoiseTotal Harmonic Distortion + Noise Measured Results5.2 Output Power Output PowerEfficiency 5.3 EfficiencyMeasured Results 5.5 Signal-to-NoiseRatio SNR 5.4 Gain and Phase ResponseGain and Phase Response Supply Ripple Rejection 5.6 Supply Ripple RejectionMeasured Results