LM4875M/NOPB - 750mW Mono Audio Amplifier w/ DC Volume | TI
MPN: LM4875M/NOPB ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $2.55 | $2.55 |
| 10 | $2.29 | $22.90 |
| 100 | $1.93 | $193.00 |
| 500 | $1.62 | $810.00 |
| 1,000 | $1.38 | $1,380.00 |
LM4875M/NOPB Overview
An audio power amplifier IC is an integrated circuit that delivers sufficient low-distortion current to drive a loudspeaker or headphone transducer from a low-voltage analog source. Within the power management hierarchy, the LM4875M/NOPB belongs to the analog amplifier family, which is a sub-category of signal-chain ICs alongside op-amps, line drivers, and codecs. Class-AB amplifiers such as the LM4875 bias their output transistors with a small quiescent current, achieving higher efficiency than Class-A designs while avoiding the crossover notch distortion of Class-B push-pull stages. The bridged (BTL) topology doubles the voltage swing across the load without requiring a DC blocking capacitor or split supply, simplifying single-rail portable designs.
Key features of the LM4875M/NOPB include 750 mW output into 8 ohm at 5 V with 0.5% THD+N, an integrated DC voltage volume control pin that sets gain in 32 steps, an automatic bridged-mode / headphone-mode sense pin, click-and-pop suppression on enable and mode transitions, and thermal shutdown protection. The supply range of 2.7 V to 5.5 V supports both single-cell Li-ion (3.7 V nominal) and USB-powered (5 V) rails, making the part well suited to handheld consumer audio. The 8-pin SOIC (M) package is JEDEC MS-012 standard with a thermal pad absent, so most dissipation is handled through the PCB copper pours on pins 4 and 5.
The device uses a fully differential Class-AB output stage with internal feedback networks, plus a switched headphone amplifier that engages when a jack is sensed. Volume is set by a DC voltage on the VOL pin rather than a logarithmic taper potentiometer, eliminating the need for a mechanical pot and allowing software or hardware mute. The depop circuit controls the output common-mode voltage during power-up and headphone insertion, suppressing the audible transient that plagues many low-cost amplifiers.
Typical applications include portable media players, USB-powered speakers, MP3 docking stations, laptop and tablet audio outputs, point-of-sale and kiosk audio prompts, and intercom / doorbell audio. The wide 2.7-5.5 V supply range and small 8-pin SOIC footprint make it a strong fit for any battery- or bus-powered design that needs more volume than a codec headphone amp can deliver.
When designing with this part, ensure the input coupling capacitors are sized for the lowest desired bass response (47 nF gives roughly -3 dB at 300 Hz into the internal 20 kohm input impedance). Provide adequate ground copper on pins 4 and 5, and keep the HP-SENSE trace short to avoid false mode switching.
This page synthesizes DigiKey/Mouser distributor pricing, drop-in same-package alternatives, and application-specific design notes not aggregated in the manufacturer datasheet, giving engineers a faster path to a verified BOM.
Drop-in alternatives for LM4875M/NOPB — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
LM4875MX/NOPB
✅ Drop-In📋 Reference alternative (not in catalog)
LM4875MM/NOPB
✅ Drop-In📋 Reference alternative (not in catalog)
LM4875M/NOPB.A
✅ Drop-In📋 Reference alternative (not in catalog)
TPA711DGN
✅ Drop-In📋 Reference alternative (not in catalog)
TPA2005D1DR
✅ Drop-In📋 Reference alternative (not in catalog)
LM4875M/NOPB Maximum Ratings & Electrical Characteristics
| Product Type | Audio Power Amplifier (Class-AB, Bridged Mono) |
| Output Channels | 1-Channel (Mono) with Mono Headphones |
| Output Power | 750 mW into 8 ohm at 5 V, 1% THD+N |
| Supply Voltage Range | 2.7 V to 5.5 V |
| Topology | Bridged (BTL) speaker + single-ended headphone amp |
| THD+N | 0.5% at 750 mW into 8 ohm (typ) |
| Volume Control | DC voltage, 32-step (internal) |
| Headphone Sense Pin | Yes (HP-SENSE auto-switches BTL / SE) |
| Depop / Click Suppression | Yes (integrated) |
| Operating Temperature | -40 C to +85 C |
| Package | 8-SOIC (3.90 mm / 0.154") |
| Mounting Type | Surface Mount |
| MSL Level | 1 (unlimited floor life) |
| Lead-Free / RoHS | Yes / Compliant |
| Manufacturer | Texas Instruments (National Semiconductor legacy) |
LM4875M/NOPB Pin Configuration
| Pin 1 | SHUTDOWN — Active-low shutdown logic input (logic high = enabled, logic low = low quiescent current) |
| Pin 2 | VOL — DC voltage volume control input; 0 V mutes, increasing DC voltage increases gain in 32 steps |
| Pin 3 | HP-SENSE — Headphone sense input; logic level selects bridged speaker mode or single-ended headphone mode |
| Pin 4 | GND — Ground (signal and thermal) |
| Pin 5 | GND — Ground (second ground pin for thermal dissipation) |
| Pin 6 | +OUT — Bridged positive output to speaker (BTL topology; -OUT is internal) |
| Pin 7 | IN — Audio analog input (AC-coupled, typically via 0.1-1 uF cap) |
| Pin 8 | VDD — Supply voltage input, 2.7 V to 5.5 V |
Typical Applications
LM4875M/NOPB is suitable for 6 applications: Portable Media Player Speaker Amplifier, USB-Powered Computer Speakers, MP3 / Bluetooth Docking Station Audio, Point-of-Sale and Kiosk Audio Prompts, Laptop and Tablet Audio Output, Intercom, Doorbell, and Access Control Audio.
Portable Media Player Speaker Amplifier
The LM4875M/NOPB is a strong fit for portable media player speaker outputs because it delivers 750 mW into an 8 ohm speaker from a single Li-ion cell (3.7 V nominal) within its 2.7-5.5 V supply window. The integrated DC volume control lets the host MCU set audio level through a DAC or PWM-filtered GPIO, eliminating a mechanical audio-taper potentiometer and saving PCB area. The bridged output topology doubles the voltage swing across the speaker without a DC blocking capacitor, preserving low-frequency response below 100 Hz that is critical for full-range music playback. The depop circuit suppresses turn-on and shutdown transients, so there is no audible thump when the player is powered up or the headphone jack is inserted.
Recommended
USB-Powered Computer Speakers
The LM4875M/NOPB works well in USB-powered computer speakers because its 5.5 V absolute maximum supply rating accepts the USB 5 V bus directly without additional regulation. At 5 V supply into 8 ohm, the part delivers 750 mW with less than 1% THD+N, sufficient for desktop near-field listening. The HP-SENSE pin enables automatic switching to a front-panel headphone jack without an external mechanical switch, a common feature on multimedia speakers. The SOIC-8 package and small external BOM (two input caps, two output caps, one bypass cap) keep the total solution under 10 components, which is critical for cost-sensitive consumer USB speakers.
Recommended
MP3 / Bluetooth Docking Station Audio
The LM4875M/NOPB is widely used in MP3 and Bluetooth docking stations where line-level audio from the dock connector must drive an internal 8 ohm speaker. Its 0.5% THD+N at full output preserves audio fidelity from the dock's digital source, and the bridged topology drives the speaker without a coupling capacitor that would otherwise roll off bass. The 32-step DC volume interface allows the dock MCU to coordinate volume changes with the source device's volume control via Bluetooth AVRCP or proprietary protocols. Integrated depop circuitry prevents audible clicks when the dock enters or exits standby, an important user-experience detail for consumer audio products.
Recommended
Point-of-Sale and Kiosk Audio Prompts
Industrial point-of-sale terminals and self-service kiosks use the LM4875M/NOPB for short audio prompts, beep tones, and voice guidance from an embedded speaker. The 2.7-5.5 V supply range accepts both 3.3 V logic-rail-derived power and 5 V USB-derived power in the same design, simplifying inventory across product variants. The DC volume control enables software-controlled loudness, useful for adjusting output level in quiet retail versus noisy industrial environments. Click-and-pop suppression is important for kiosks that power-up and power-down frequently, since un-suppressed transients would be highly noticeable to users standing close to the device.
Recommended
Laptop and Tablet Audio Output
The LM4875M/NOPB serves as a Class-AB mono speaker amplifier in laptop and tablet designs that need more output than the codec's integrated headphone amp can provide. Its bridged topology drives the internal 8 ohm speaker with full bass response, complementing the headphone-only output of the main codec. The integrated headphone switch allows the same amplifier section to feed external headphones when plugged in, sharing circuitry between speaker and headphone modes and reducing BOM cost. The lack of a switching Class-D stage means no EMI coupling into nearby Wi-Fi, Bluetooth, or touchscreen sense circuitry - a major reliability advantage in dense mobile platforms.
Recommended
Intercom, Doorbell, and Access Control Audio
The LM4875M/NOPB fits intercom, doorbell, and access-control panel audio where short voice prompts or chime tones need to be loud and intelligible. Its 750 mW output into 8 ohm provides ample volume for entryways, while the wide 2.7-5.5 V supply range accepts both 3.3 V system-rail power and 5 V from PoE or USB-C adapters. The thermal shutdown protection prevents failure in outdoor installations where the amplifier might be driven into continuous output during tampering or fault conditions. The integrated depop circuit eliminates the turn-on thump that would otherwise be heard through the wall-mounted speaker, an important detail for residential and commercial intercom installations.
Recommended
Recommended Products Summary
Engineering reference data for LM4875M/NOPB — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | LM4875MX/NOPB | LM4875MM/NOPB | LM4875M/NOPB.A | TPA711DGN | TPA2005D1DR |
|---|---|---|---|---|---|---|
| Package | 8-SOIC (3.90 mm) | 8-SOIC wide body - same | MSOP-8 - different (smaller) | 8-SOIC - same | MSOP-8 PowerPAD - different | SOIC-8 PowerPAD - different (with thermal pad) |
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments |
| Output Power (8 ohm, 5 V) | 750 mW | 750 mW | 750 mW | 750 mW | 700 mW (-7%) | 1.1 W (+47%) |
| Supply Voltage Range | 2.7 V to 5.5 V | 2.7 V to 5.5 V | 2.7 V to 5.5 V | 2.7 V to 5.5 V | 2.5 V to 5.5 V | 2.5 V to 5.5 V |
| Volume Control Interface | DC voltage, 32 steps | DC voltage, 32 steps | DC voltage, 32 steps | DC voltage, 32 steps | Fixed gain (external resistors) | Fixed gain (external resistors) |
| Headphone Switch | Yes (HP-SENSE auto-switch) | Yes | Yes | Yes | No (speaker only) | No (speaker only) |
| Depop / Click Suppression | Yes (integrated) | Yes | Yes | Yes | Yes | Yes |
| Topology | BTL speaker + SE headphone | BTL + SE | BTL + SE | BTL + SE | BTL speaker only | BTL speaker only |
Key Differentiators
- Integrated 32-step DC volume control eliminates mechanical potentiometer (vs TPA711DGN)
- Integrated bridged-mode / headphone-mode auto-switching (vs TPA2005D1DR)
- Higher output power than fixed-gain alternatives (vs TPA711DGN)
Design Notes
Estimated: at 5 V supply delivering 750 mW into 8 ohm, the LM4875M/NOPB draws roughly 250 mA average and dissipates approximately 1.6 W internally as heat (P_diss = VDD*IQ_avg + (VDD - V_OUT)*I_OUT for a bridged stage). The 8-SOIC package has no exposed thermal pad; thermal resistance theta_JA is approximately 170 C/W on a 1-oz 4-layer JEDEC test board. To stay below 125 C junction at 25 C ambient, dissipation must remain under roughly 0.6 W - so provide at least 1 square inch of copper pour on pins 4 and 5 plus GND copper on the top and bottom layers, or reduce sustained output power for continuous-tone applications.
Place the input coupling capacitor (typically 0.1-1 uF) as close as possible to pin 7 (IN) to minimize noise pickup on the high-impedance input node. Place the VDD bypass capacitor (1 uF ceramic plus 10 uF bulk) within 5 mm of pin 8 (VDD) and connect the ground side directly to pin 4 / pin 5 ground copper. Keep the HP-SENSE trace (pin 3) short and routed away from the speaker output traces (pin 6) to prevent false mode switching from capacitive coupling during high-volume playback.
Do not load the LM4875M/NOPB with less than 8 ohm impedances (e.g. 4 ohm speakers) at 5 V supply - the resulting current draw can trigger thermal shutdown and may damage the output stage over time. Ensure the VOL pin is never left floating; tie it to a defined DC level (typically half-VDD through a resistor divider or to a DAC) - a floating VOL pin can cause unpredictable gain or mute behavior depending on internal bias currents. Do not apply DC offset above 0.5 V to the audio input (pin 7); use a series coupling capacitor of at least 0.1 uF to block DC.
Compliance Information
RoHS compliant and lead-free per TI product page. The /NOPB suffix indicates lead-free terminal finish. Originally a National Semiconductor part number; now manufactured and supported by Texas Instruments. Not AEC-Q100 qualified - for automotive audio amplifier applications, evaluate the TPA2005D1DR-Q1 or similar automotive-grade TI part.
