The SSM22111 is a high performance audio amplifier that delivers 1 W RMS of low distortion audio power into a bridge-connected 8 ? speaker load (or 1.5 W rms into a 4 ? load).

The SSM2211 operates over a wide temperature range and is specified for single-supply voltages between 2.7 V and 5.5 V. When operating from batteries, it continues to operate down to 1.75 V. This makes the SSM2211 the best choice for unregulated applications, such as toys and games.

Featuring a 4 MHz bandwidth and distortion below 0.2% THD + N @ 1 W, superior performance is delivered at higher power or lower speaker load impedance than competitive units. Furthermore, when the ambient temperature is at 25?C, THD + N < 1%, and VS = 5 V on a four-layer PCB, the SSM2211 delivers a 1.5 W output.

The low differential dc output voltage results in negligible losses in the speaker winding and makes high value dc blocking capacitors unnecessary. The battery life is extended by using shutdown mode, which typically reduces quiescent current drain to 100 nA.

Download the datasheet document of SSM2211 for 1.5W audio amplifier circuit reference:

SSM2211 Datasheet

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Download Datasheet

Schematic diagram:

PCB layout:

Power Supply Circuit:

This amplifier require dual polarity output power supply (+, ground and -). Use this power supply circuit:

Transformer: 3-5 Ampere, 24V secondary output
Diode: Diode bridge 5A or 4 piece of single diode 5A

This circuit is quite simple but will give you high quality audio output. Take a note that above diagram designed for single input and single output (mono system). For stereo system, you need to build two similar circuits.

The input stage is an LF351 op amp which provides most of the open loop gain as well as stabilizes the quiescent dc voltage. This feeds a level shift stage which references the voltage swing to the (-) rail. The transconductance stage is a darlington, to improve high-frerqency linearity. The 2SC2344 by itself has a rather large collector-base capacitance which is voltage dependent. The MPSA42 presents this with a low-z and has a C(ob) of only a few pf that is effectively swamped by the 33pF pole-splitting cap. The stage is supplied by the 2SA1011 active load (current source) which is about 20 ma. The current to the stage is limited by the 2N3094 to about 70 ma under worst case.

The output is a full complementary darlington with paralleled outputs. Although you could “get away with” only one if only 8 ohm easy-to-drive loads are used, this is not recommended. The use of parallel devices increases the ability to drive reactive loads (which can pull a significant current while the voltage waveform crosses zero and puts a high voltage and a high curent across the transistor simultaneously), gives the amp a higher damping factor, and reduces the maximum current each transistor has to supply to peaks (remember, the gain of a power transistor drops as the current increases).

Compensation is two-pole and one zero. The op-amp’s pole and the pole generated by the 33pf cap and the 470 ohm bias resistor of the MPSA42 dominate. (the 33pF gets multiplied by the stage gain.) The 22 pf feedback capacitor provides lead compensation, and is taken from the output of the tranconductance stage rather than the output itself. In this way, the phase lag introduced by the output transistors is not seen by the high-frequency feedback. This intorduces a closed-loop pole which limits the high-frequency response. The two compensation capacitors must be type 1 creamic (NPO) or silver mica – with ZERO voltage coefficient.

The 100W RMS audio amplifier circuit was designed to run 2 channels off a +/- 55 volt unregulated supply, reducing to +/- 48 volts under full load. It used a 40-0-40 volt, 5 amp toroid transformer, a bridge rectifier, and 10,000 uf of filter cap per side. If a standard EI transformer is used, a 6-amp rated unit should be used. With this power supply, it produces 100 watts continuous, both channels driven into 8 ohms resistive with no clipping. Dynamic headroom is about a db and a half. For more headroom, unloaded voltages to +/- 62 volts can be used with no circuit modification.

Read detail explanation about this 100W RMS audio amplifier HERE
Download large schematic diagram in PDF format HERE