PAM8403

A 3 W + 3 W filterless class-D stereo amplifier board that drives two 4 to 8 ohm speakers from a 5 V supply.

Supply voltage2.5 V to 5.5 V (DFR0119 board: 3.6 V to 5.5 V)
Absolute maximum supply6.0 V
Output power at 5 V, 4 ohm3.2 W per channel at 10 % THD+N, 2.5 W at 1 %
Output power at 5 V, 8 ohm1.8 W per channel at 10 % THD+N, 1.4 W at 1 %

In short

The PAM8403 is a filterless class-D stereo amplifier: at 5 V it delivers 3.2 W per channel into 4 ohm or 1.8 W into 8 ohm at 10 % THD, with a fixed 24 dB gain (Diodes PAM8403 datasheet DS36439, p. 4). It runs from 2.5 V to 5.5 V and is destroyed above 6 V (pp. 3, 4). Feed line-level audio into LIN and RIN, and wire each speaker between its own + and - outputs, never to ground.

Class-D amplifiers switch their outputs at high frequency and let the speaker coil average the result, which is why the PAM8403 reaches up to 90 % efficiency (Diodes datasheet, p. 1) and stays cool on a small board. Its outputs are bridge-tied: each speaker connects between L+ and L- (or R+ and R-), and both terminals carry the switching signal.

The chip's gain is fixed at 24 dB (datasheet, p. 4), so a line-level signal of a few hundred millivolts already drives it to full power. A GPIO's 3.3 V or 5 V square wave is far too large; attenuate it with a resistor divider and couple it through a capacitor, as the datasheet's input capacitor guidance describes (p. 8).

DFRobot's Fermion breakout (DFR0119) brings out LIN, RIN, two grounds, VCC and an active-low SHDN on one header and L+, L-, R-, R+ on the other. It wants 3.6 V to 5.5 V, and SHDN can be left open for normal operation (DFRobot DFR0119 wiki). Generic green PAM8403 boards with a volume knob use the same chip and the same rules.

PAM8403 pinout

Pin	Function	Type
LIN	Audio in, leftLine level, a few hundred mV	input
GND1	GND	power in
RIN	Audio in, right	input
VCC	VCC3.6 V to 5.5 V	power in
GND2	GND	power in
SHDN	Shutdown (active low)	input
LP	Speaker	output
LM	Speaker	output
RM	Speaker	output
RP	Speaker	output

How to wire the PAM8403

Pin by pin, for the board you have.

PAM8403	Arduino Uno	Note
VCC	5V
GND2	GND
LIN	D8	Through a divider and capacitor: D8, 10 kOhm, a node with 1 kOhm to GND, then 1 µF into LIN.
GND1	GND
SHDN	D7	HIGH runs the amplifier, LOW mutes it to under 1 µA.
LP	Speaker +
LM	Speaker -

Never connect L- or R- to GND: both outputs switch, and grounding one shorts the amplifier.
Use a 4 ohm or 8 ohm speaker. At full power on 4 ohm the board draws well over 1 A from 5 V, more than the Uno's USB supply; keep the volume moderate or use a separate 5 V supply with shared ground.

Design this circuit on an Arduino Uno

PAM8403	ESP32 DevKit V1	Note
VCC	VIN	5 V from USB.
GND2	GND
LIN	GPIO25 (D25)	Through 10 kOhm, a node with 1 kOhm to GND, then 1 µF into LIN.
GND1	GND
SHDN	GPIO26 (D26)	3.3 V HIGH runs it, LOW mutes it.
LP	Speaker +
LM	Speaker -

Power VCC from 5 V (VIN), not from 3V3: the speaker current would overload the ESP32's regulator.
Never ground L- or R-.

Design this circuit on an ESP32 DevKit V1

PAM8403	Raspberry Pi Pico	Note
VCC	VBUS	5 V from USB.
GND2	GND
LIN	GP15	Through 10 kOhm, a node with 1 kOhm to GND, then 1 µF into LIN.
GND1	GND
SHDN	GP14	HIGH runs it, LOW mutes it.
LP	Speaker +
LM	Speaker -

Feed VCC from VBUS or a separate 5 V supply, never from 3V3(OUT), whose load should stay under 300 mA (Raspberry Pi Pico datasheet, p. 9).
Never ground L- or R-.

Design this circuit on a Raspberry Pi Pico

PAM8403 code

Every example here compiles for its board.

No library needed

// PAM8403 on Arduino Uno: wiring and a free simulation at https://www.tinkered.ai/components/pam8403
// PAM8403 on an Arduino Uno: tone on D8 (through 10k/1k divider and 1 uF) into LIN, SHDN on D7.
const int AUDIO_PIN = 8;
const int SHDN_PIN = 7;
const int NOTES[] = {262, 294, 330, 349, 392, 440, 494, 523}; // C4 to C5 in Hz

void setup() {
  Serial.begin(115200);
  pinMode(SHDN_PIN, OUTPUT);
  digitalWrite(SHDN_PIN, LOW);  // keep it asleep while the supply settles
  delay(10);
  digitalWrite(SHDN_PIN, HIGH); // then enable the amplifier
  Serial.println("PAM8403 ready");
}

void loop() {
  for (int i = 0; i < 8; i++) {
    Serial.print("Note ");
    Serial.print(NOTES[i]);
    Serial.println(" Hz");
    tone(AUDIO_PIN, NOTES[i], 300);
    delay(350);
  }
  digitalWrite(SHDN_PIN, LOW); // mute between scales
  Serial.println("Muted");
  delay(1500);
  digitalWrite(SHDN_PIN, HIGH);
}

Compiled for arduino:avr:uno on 2026-10-30

No library needed

// PAM8403 on ESP32 DevKit V1: wiring and a free simulation at https://www.tinkered.ai/components/pam8403
// PAM8403 on an ESP32 DevKit V1: tone on GPIO25 (through 10k/1k divider and 1 uF) into LIN, SHDN on GPIO26.
const int AUDIO_PIN = 25;
const int SHDN_PIN = 26;
const int NOTES[] = {262, 294, 330, 349, 392, 440, 494, 523};

void setup() {
  Serial.begin(115200);
  pinMode(SHDN_PIN, OUTPUT);
  digitalWrite(SHDN_PIN, LOW);
  delay(10);
  digitalWrite(SHDN_PIN, HIGH);
  Serial.println("PAM8403 ready");
}

void loop() {
  for (int i = 0; i < 8; i++) {
    Serial.printf("Note %d Hz\n", NOTES[i]);
    tone(AUDIO_PIN, NOTES[i], 300);
    delay(350);
  }
  digitalWrite(SHDN_PIN, LOW);
  Serial.println("Muted");
  delay(1500);
  digitalWrite(SHDN_PIN, HIGH);
}

Compiled for esp32:esp32:esp32 on 2026-10-30

No library needed

// PAM8403 on Raspberry Pi Pico: wiring and a free simulation at https://www.tinkered.ai/components/pam8403
// PAM8403 on a Raspberry Pi Pico (arduino-pico): tone on GP15 (through 10k/1k divider and 1 uF) into LIN, SHDN on GP14.
const int AUDIO_PIN = 15;
const int SHDN_PIN = 14;
const int NOTES[] = {262, 294, 330, 349, 392, 440, 494, 523};

void setup() {
  Serial.begin(115200);
  pinMode(SHDN_PIN, OUTPUT);
  digitalWrite(SHDN_PIN, LOW);
  delay(10);
  digitalWrite(SHDN_PIN, HIGH);
  Serial.println("PAM8403 ready");
}

void loop() {
  for (int i = 0; i < 8; i++) {
    Serial.print("Note ");
    Serial.print(NOTES[i]);
    Serial.println(" Hz");
    tone(AUDIO_PIN, NOTES[i], 300);
    delay(350);
  }
  digitalWrite(SHDN_PIN, LOW);
  Serial.println("Muted");
  delay(1500);
  digitalWrite(SHDN_PIN, HIGH);
}

Compiled for rp2040:rp2040:rpipico on 2026-10-30

Before you wire it

Keep the supply between 2.5 V and 5.5 V (Diodes datasheet, p. 4); four fresh alkaline cells exceed 6 V and can kill it, so use three cells or four NiMH (p. 7).
Wire each speaker between its own + and - outputs, with nothing else on them.
Attenuate a GPIO signal before LIN or RIN: the 24 dB gain (datasheet, p. 4) clips a full logic-level square wave.
Couple sources through a capacitor; the input must stay within -0.3 V to VDD + 0.3 V (datasheet, p. 3).
Decouple the supply near the board with about 1 µF ceramic plus 20 µF or more, as the datasheet recommends (p. 8).

Don’t

Never ground L- or R-, or join the two channels' outputs: the outputs are bridge-tied.
Never feed the outputs into another amplifier's input; they are a switching signal for a speaker coil.
Never power it from a 3.3 V regulator pin at full volume: 3 W into a speaker means well over half an amp.
Never exceed 6 V on VCC, even briefly (datasheet, p. 3).

Gain is 20 log(2 x RF/RI) and the chip limits it to 24 dB (datasheet, p. 7); the board has no gain setting, so control volume at the source or with a potentiometer before LIN and RIN.
The input capacitor and the chip's input resistance form a high-pass filter; small speakers reproduce little below 100 to 150 Hz anyway, so 0.47 µF to 1 µF is plenty (datasheet, p. 8).
The 10 kOhm and 1 kOhm divider in the wiring turns a 5 V square wave into about 0.45 Vpp, a usable line level.
Short-circuit protection disables the outputs if they are shorted to each other or to ground, and thermal shutdown protects the chip (datasheet, pp. 1, 8).
Hold SHDN low for about 10 ms after power-up before enabling, to reduce the turn-on pop.

Specifications

Supply voltage: 2.5 V to 5.5 V (DFR0119 board: 3.6 V to 5.5 V)Diodes PAM8403 datasheet DS36439, p. 4; DFRobot DFR0119 wiki
Absolute maximum supply: 6.0 VDiodes PAM8403 datasheet DS36439, p. 3
Output power at 5 V, 4 ohm: 3.2 W per channel at 10 % THD+N, 2.5 W at 1 %Diodes PAM8403 datasheet DS36439, p. 4
Output power at 5 V, 8 ohm: 1.8 W per channel at 10 % THD+N, 1.4 W at 1 %Diodes PAM8403 datasheet DS36439, p. 4
Gain: 24 dB fixedDiodes PAM8403 datasheet DS36439, pp. 4, 7
Efficiency: Up to 90 %Diodes PAM8403 datasheet DS36439, p. 1
Quiescent current: 10 mA at 3.6 V, no load; under 1 µA in shutdownDiodes PAM8403 datasheet DS36439, p. 4
Input voltage range: -0.3 V to VDD + 0.3 VDiodes PAM8403 datasheet DS36439, p. 3
SHDN on the breakout: Low puts the amplifier to sleep; open or high runs itDFRobot DFR0119 wiki

From the PAM8403 Filterless 3W Class-D Stereo Audio Amplifier, DS36439 Rev. 2-3, published by Diodes Incorporated.

Common mistakes

Speaker minus to ground
With most amplifiers the speaker's negative goes to ground; with the PAM8403 both outputs switch (bridge-tied). Grounding L- shorts an output and the short-circuit protection shuts the channel down (Diodes datasheet, p. 8).
Four AA batteries
Four fresh alkaline cells measure over 6 V, above the 6.0 V absolute maximum (datasheet, pp. 3, 7). Use three alkaline cells, four NiMH cells or a regulated 5 V supply.
Distorted, very loud beeps
A 5 V square wave straight into LIN, multiplied by the 24 dB gain, clips hard. Add the 10 kOhm and 1 kOhm divider and a coupling capacitor, or turn down the source.
Noise and hum
Long input wires pick up the class-D switching and USB noise. Keep audio wires short, share a single ground point and add the supply capacitors the datasheet recommends (p. 8).

PAM8403 questions

How much power does the PAM8403 really give?

At 5 V into 4 ohm, 3.2 W per channel at 10 % distortion or 2.5 W at 1 %; into 8 ohm, 1.8 W and 1.4 W (Diodes datasheet, p. 4). At 3.6 V the figures drop by about half.

PAM8403 vs LM386: which amplifier should I use?

The PAM8403 is a stereo class-D amplifier, up to 90 % efficient (datasheet, p. 1), giving watts from 5 V. The LM386 is a mono class-AB amplifier giving well under a watt and wasting more power as heat. For battery and USB projects the PAM8403 is the better choice.

Can I connect the PAM8403 to an Arduino?

Yes, for beeps and simple tones: use tone() on a pin, a 10 kOhm and 1 kOhm divider and a 1 µF capacitor into LIN. For music, feed it from a DAC or an MP3 module such as the DFPlayer Mini.

What does the SHDN pin do?

Pulling it low shuts the amplifier down to under 1 µA (datasheet, p. 4). On the DFRobot board it runs when the pin is left open (DFR0119 wiki), so you only need to wire it to mute from code.

Can I use one speaker with both channels?

Not by joining the outputs. Use one channel for one speaker, or mix left and right through two resistors into a single input if you want both signals in one speaker.

Build something with the PAM8403

Desktop speaker pair
Amplify a phone or PC line output into two small speakers.
Build this
Doorbell chime
Play a melody through a speaker when a button is pressed.
Build this
Audio alarm for a sensor
Sound a loud alert from a gas or water sensor.
Build this

For AI assistants

This page as plain Markdown, for ChatGPT, Claude or your own agent. /components/pam8403.md

PAM8403

Speaker minus to ground

Four AA batteries

Distorted, very loud beeps

Noise and hum

PAM8403 questions

Desktop speaker pair

Doorbell chime

Audio alarm for a sensor

What will you build with it?