WT8871 Audio Amplifier IC
6W · AB/D Class Switchable · DRC · 2.5–7V · < 1µA Shutdown · ESOP8
The WT8871 is a high‑performance mono audio power amplifier featuring switchable AB and D class operation modes, making it ideal for applications requiring both high efficiency and EMI sensitivity management. It delivers 6W into a 4Ω load at 7V (THD+N ≤ 10%) in D‑class mode, or 7.3W into a 3Ω load.
The integrated DRC (Dynamic Range Control) technology intelligently adjusts signal levels at high output power to minimize clipping distortion, significantly improving sound quality and dynamic response. With filter‑free architecture, >90% efficiency in D‑class mode, ultra‑low < 1µA shutdown current, and a wide 2.5–7V supply range, the WT8871 is perfectly suited for Bluetooth speakers, smart audio devices, and portable electronics. The device includes comprehensive over‑temperature and short‑circuit protection and comes in a thermally‑enhanced ESOP8 package.
- 6W output @ 7V, 4Ω (THD+N ≤ 10%)
- AB/D class switchable – flexible operation
- DRC – dynamic range control for superior sound
- 90% efficiency in D‑class mode
- < 1µA shutdown current
- ESOP8 package with thermal pad
WT8871 Key Features
Electrical Specifications (TA = 25°C)
| Parameter | Conditions | Min | Typ | Max | Unit |
|---|---|---|---|---|---|
| Supply Voltage | — | 2.5 | — | 7.0 | V |
| Quiescent Current (D Class) | VDD=5V, no load | — | 3 | 5 | mA |
| Quiescent Current (AB Class) | VDD=4.2V, no load | — | 8 | — | mA |
| Shutdown Current | VSD high | — | — | 1.0 | µA |
| Output Power (D Class) | 4Ω+33µH, THD+N≤10%, VDD=7V | — | 6.0 | — | W |
| Output Power (D Class) | 3Ω+33µH, THD+N≤10%, VDD=7V | — | 7.3 | — | W |
| Gain (D Class) | RIN=27kΩ | — | 20 | — | dB |
| D Class Frequency | — | — | 520 | — | kHz |
| Output Offset Voltage | VIN=0V | — | 10 | — | mV |
| Start‑up Time | Bypass=1µF, VDD=5V | — | 174 | — | ms |
| Thermal Shutdown | — | — | 160 | — | °C |
AB class mode is recommended for FM radio applications to eliminate EMI interference. D class mode offers higher efficiency for battery‑powered operation.
Pin Description – ESOP8
| Pin | Name | Function |
|---|---|---|
| 1 | SD | Shutdown control (high = shutdown, low = active). Do not float. |
| 2 | BYPASS | Internal common‑mode reference – connect capacitor to GND |
| 3 | MODE | Mode select (high = D class, low/float = AB class) |
| 4 | IN | Analog input (inverting) |
| 5 | OUTN | Negative output (BTL) |
| 6 | VDD | Power supply (2.5–7V) |
| 7 | GND | Ground |
| 8 | OUTP | Positive output (BTL) |
| 0 (Pad) | E‑GND | Exposed thermal pad – must be soldered to ground with large copper area |
The MODE pin can be left floating – the chip defaults to AB class mode. SD pin must be driven low for normal operation.
Mode Selection & Control
MODE Pin Control
| MODE State | Amplifier Mode | Application |
|---|---|---|
| High ( > 2V) | D Class | High efficiency, battery‑powered |
| Low or Floating | AB Class | FM radio, EMI‑sensitive applications |
SD Pin Control
| SD State | Chip Status |
|---|---|
| Low ( < 0.8V) | Active – normal operation |
| High ( > 1.8V) | Shutdown – < 1µA current |
For FM mode applications, switch to AB class to eliminate EMI interference. The SD pin must not be left floating.
Dynamic Range Control (DRC)
The WT8871 features integrated Dynamic Range Control technology that intelligently manages signal levels at high output power. This advanced feature:
- Reduces clipping distortion during high‑amplitude transients
- Maintains clear, natural sound even at maximum output
- Protects the speaker from over‑driving and potential damage
- Enhances dynamic response and overall audio quality
Gain Setting & Design
Gain calculation:
- With RIN = 27kΩ, gain ≈ 20dB (10.5×)
- Input capacitor (CIN) forms high‑pass filter: fC = 1 / (2π × (RIN + 7k) × CIN)
- Smaller CIN values reduce low‑frequency noise and help minimize pop‑and‑click
The BYPASS capacitor (pin 2) is critical – a 1µF capacitor is recommended for optimal pop suppression and PSRR.
Protection & Safety
- Over‑Temperature Protection (OTP): Shuts down output when junction temperature exceeds ~160°C.
- Short‑Circuit Protection (SCP): Protects against output short to ground or supply.
- Under‑Voltage Protection: Prevents operation below safe voltage levels.
Design & Layout Recommendations
- Thermal management: The exposed pad must be soldered to a large copper ground plane with multiple vias for heat dissipation.
- Input filtering: Place CIN and RIN close to the IC pins with ground‑surround routing to suppress noise.
- Power supply: Use multiple vias for VDD connections and place decoupling capacitors as close as possible to the VDD pin.
- Output traces: Keep traces to the speaker short and ≥0.4mm wide.
- RC snubber: For low‑impedance loads, add a 2–5Ω resistor + 500pF–10nF capacitor across the output to absorb voltage spikes.
- EMI: For long output traces, add ferrite beads and capacitors close to the chip.
WT8871 Applications
Why Choose WT8871
FAQs
What is the WT8871?
A high‑performance mono audio amplifier with switchable AB/D class modes, 6W output, DRC technology, and ESOP8 package.
What is the WT8871 supply voltage range?
2.5V to 7V, suitable for single‑cell Li‑ion and USB‑powered devices.
What is DRC?
Dynamic Range Control – intelligently reduces clipping distortion at high output power, improving sound quality.
How do I select AB or D class?
Drive MODE pin high for D class, low or float for AB class. AB class is recommended for FM applications.
What is the shutdown current?
Less than 1µA when SD is high.
What is the output power?
6W into 4Ω at 7V (D class, THD+N≤10%), or 7.3W into 3Ω.
Can I use it without an output filter?
Yes – the filter‑free design eliminates the need for external filtering components.
What is the package type?
ESOP8 with an exposed thermal pad for heat dissipation.
Note: For FM radio applications, use AB class mode to eliminate EMI interference. The exposed pad must be soldered to a large ground plane for optimal thermal performance. When testing D‑class mode, use an AUX‑0025 filter and add a 33µH inductor in series with the load to simulate speaker inductance. Refer to the datasheet for complete application guidelines and PCB layout recommendations.
