Audio amplifier module

01

Read power ratings at a stated distortion, load and supply

Texas Instruments' TPA3255 datasheet (a Class-D amplifier IC) lists output power per channel at 51 V supply and a 75 °C case temperature: 315 W into 4 Ω at 10% THD+N but 255 W at 1% THD+N; at 53.5 V, 250 W and 200 W into 6 Ω and 195 W and 155 W into 8 Ω. It quotes 0.006% THD+N at 1 W into 4 Ω, about 112 dB SNR, 85 µV A-weighted output noise, and 2.5 W idle loss with four channels switching. [1]

The datasheet's feature list gives 90% efficient Class-D operation into 4 Ω and a supply range of 18–53.5 V, and describes stereo, mono (bridged) and 2.1 or 4 × single-ended configurations. [1]

Lower-power modules use smaller chips. TI's TPA3116D2 family lists 2 × 50 W into 4 Ω BTL at 21 V (TPA3116D2), 2 × 30 W into 8 Ω at 24 V (TPA3118D2) and 2 × 15 W into 8 Ω at 15 V (TPA3130D2) from a single 4.5–26 V supply, with over 90% efficiency, switching up to 1.2 MHz with AM avoidance, a programmable power limit and stereo or mono modes. TI's TAS5825M, a digital-input closed-loop Class-D amplifier, lists 2 × 30 W into 8 Ω at 24 V at 1% THD+N and 2 × 38 W at 10%, or 1 × 53 W and 1 × 65 W into 4 Ω at 22 V, from 4.5–26.4 V. [2] [3]

Editorial calculation: the TAS5825M's stereo rating rises from 30 W to 38 W per channel between 1% and 10% THD+N, about 27% (38 ÷ 30), similar to the TPA3255's 24% step, so compare modules only at the same distortion figure. [3] [1]

Editorial calculation: the 10% THD+N figure is about 24% higher than the 1% figure (315 ÷ 255) for the same chip and load; at 90% efficiency, 2 × 200 W of output draws about 444 W from the supply and leaves about 44 W to remove as heat. Ask module suppliers for power at 1% THD+N into your impedance and supply. [1]

Infineon's MA5332MS, a multichip module listed as active and preferred, integrates a dual-channel PWM controller, a high-voltage gate driver and four low-RDS(on) MOSFETs in a 7 × 7 mm 42-pin IQFN package. Infineon lists 2 × 200 W into 4 Ω at 10 % THD+N, 95 % efficiency at 2 × 200 W into 4 Ω, operation without a heat sink at 2 × 100 W, a split ±25 V or single 50 V supply, differential or single-ended inputs, 2 × SE, BTL and parallel-SE output modes, and OCP, OTP and UVLO protection with clip and fault reporting outputs. [4]

Editorial calculation: at Infineon's 95 % efficiency, 2 × 200 W of output draws about 400 ÷ 0.95 ≈ 421 W and leaves about 21 W of heat, against about 44 W for 2 × 200 W at the 90 % TI figure above; both are 10 % THD+N or chip-level figures, so the module's heat sink must still be sized from the supplier's test at your supply, load and enclosure temperature. [4] [1]

Give the supplier the number of channels and configuration, speaker impedance, required power at a stated THD+N, supply voltage and source, input type and level, gain, SNR and noise targets, protection features, size and mounting, heat sink and airflow, EMC and safety requirements, and quantities.

02

Check the measurement filters and the cooling behind the rating

TI warns that audio analysers can give incorrect readings of Class-D amplifier performance because of out-of-band noise at the output, and recommends AES17 plus AUX-0025 pre-analyser filters; without them a 30 kHz low-pass filter (10 Ω and 47 nF) can reduce the remaining out-of-band noise. Its electrical characteristics are measured with AES17 plus AUX-0025 filters and a specified LC output filter. [1]

TI also states that thermal performance depends on the heat sink design and the surroundings, such as a closed box without airflow or a fanned system, so the maximum continuous output power is influenced by thermal design; its thermal data assume an 85 °C heat sink with thermal compound. [1]

The TAS5825M lists THD+N of 0.03% at 1 W and 1 kHz at 12 V, 110 dB A-weighted SNR, 35 µV rms idle channel noise and quiescent current under 20 mA at 12 V; it accepts I²S, left- or right-justified or TDM audio at 32–192 kHz and adds DRC, EQ, bass enhancement and speaker thermal and excursion protection. Both TI families integrate over-current, over-temperature and under- or over-voltage protection with fault reporting. [3] [2]

Editorial note: ask module suppliers which filter and analyser they used, the case or heat-sink temperature during the power test, and how long full power can be held in your enclosure.

03

High-power, mid-power and digital-input Class-D boards

The reviewed data sheets cover high-power analogue-input Class-D stages for hundreds of watts per channel (TPA3255), mid-power analogue-input stereo amplifiers for 15–50 W per channel (TPA3116D2 family), and digital-input amplifiers with built-in audio processing for smart and wireless speakers (TAS5825M). [1] [2] [3]

Listings include 2.1-channel digital amplifier boards built on Class-D amplifier ICs, alongside power supply modules.

04

Class-D IC, output LC filter, supply decoupling, protection and heat sink

The heat sink decides how much of the IC's rating the module can hold: TI ties maximum continuous output power to heat-sink design and enclosure airflow, and Infineon states heat-sink-less operation only up to 2 × 100 W on its 2 × 200 W part. [1] [4]

05

Power at 1% THD+N, distortion, SNR, supply range and load for a module quotation

Ask for the power row at 1% THD+N: the reviewed datasheets put their 10% figures 24–27% higher for the same chip and load. [1] [3]

06

Send the channel, load and power data together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Channels: [number; configuration]
Load: [impedance]
Power: [W per channel at 1% THD+N]
Supply: [voltage; source]
Performance: [SNR; THD+N; gain]
Build: [heat sink; size; protection; EMC]

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