Lm4808 Headphone Amplifier Homemade Diy

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Lm4808 headphone amplifier for homemade DIY, it is a stereo amplifier for headphones capable of providing up to 105mW per channel with low distortion. Its small size makes it capable of being inserted in small spaces.

Schematic headphone amplifier homemade diy

Schematic Lm4808 Headphone Amplifier Homemade Diy — Schematic

About the LM4808 integrated circuit (LM4808MM, LM4808MMX, LM4808MX).

Available in SMD WSON, VSSOP, and 8-pin SOIC packages.
It features noise suppression (pop) when turning off.
It requires few external components and can be used as a headphone amplifier or audio preamplifier for home use.
The gain can be adjusted by changing the resistor values.
It can deliver up to 105mW of power per channel. It operates with voltages from 2 to 5.5V, ideally 5V.
It can also work with 3.7V batteries. Power consumption is up to 3mA.

About the circuit

Amplifying the lowest audio frequencies requires high-value input and output coupling capacitors (C2 and C3 int the schematic). A high-value capacitor can be expensive and may compromise space efficiency in portable designs. In numerous instances, however, the speakers used in portable systems, whether internal or external, have little ability to
reproduce signals below 150Hz. Applications using speakers with this limited frequency response reap little improvement by using high-value input and output capacitors.
Besides affecting system cost and size, Ci has an effect on the LM4808’s click and pop performance. The magnitude of the pop is directly proportional to the input capacitor’s size. Thus, pops can be minimized by selecting an input capacitor value that is no higher than necessary to meet the desired −3dB frequency.
As shown in the schematic, the input resistor, RI, and the input capacitor, CI, produce a −3dB high pass filter cutoff frequency that is found using Equation. In addition, the output load RL, and the output capacitor CO, produce a -3db high pass filter cutoff frequency defined by Equation.

fI_-3db = 1/2πR_IC₂
fO_-3db=1/2πR_LC₈

You can use an RC filter calculator, where RL is 20k at the input and the impedance of the headphone at the output. In our circuit, FC = 3.61 Hz at the input and 49 Hz at the output for a load of 32 Ohms.

Besides minimizing the input capacitor size, careful consideration should be paid to the value of the bypass capacitor, C1. Since C1 determines how fast the LM4808 settles to quiescent operation, its value is critical when minimizing turn-on pops. The slower the LM4808’s outputs ramp to their quiescent DC voltage (nominally 1/2 VDD), the smaller the turn-on pop. Choosing CB equal to 1.0μF or larger, will minimize turn-on pops. As discussed above, selecting C2 no larger than necessary for the desired bandwidth helps minimize clicks and pops.

The power supply should be from a source with good filtering, ranging from 2 to 5.5V, usually 5V. Batteries or batteries can also be used, as they have low consumption. T

To change the gain, the resistors R3, R5, R4, and R6 must be altered.

Gain = R3/R5.

In our application, the gain is 10.

Suggestion for a printed circuit board (PCB) to assemble the headphone amplifier.

Lm4808 Pcb Component View — Lm48Mx Pcb Component View

See also:

BOM to assemble the headphone amplifier

Last updated: 18/11/2023 13:26

Parts	Value	Description	Quantity
Capacitors
C2, C3	2.2uF	0603	2
C4, C8, C9	100uF	SMD electrolytic capacitor — 6,6 × 6,3	3
C7	100n	0603	1
Semiconductors
IC2	LM4808	SOIC8 or VSSOP8- 105-mW, stereo, analog input headphone amplifier	1
Resistors 1/4W
R3, R4	3.9K	0603–392	2
R5, R6	39K	0603–393	2
Miscellaneous
Solder, Wires, PCB, Box, power supply.