Here it is shown and explained how to build powerful 3W audio amplifier to drive a speaker with LM741 op amp. The 741 operational amplifier IC like LM741 or uA741 are old but still popular op-amp that can be used for many electronics projects. Here electronics hardware design of 3W audio amplifier with LM741 op-amp is shown. There are many types of electronic circuits for amplifiers- like pre-amplifiers which are used to amplify small signals from microphones and audio amplifier which are used to drive loud speakers. In the previous tutorial we explained with electronic schematic of how to make Magnetic Mic Pre-amplifier using uA741 op-amp.
The electronics schematics diagram of the 3W audio amplifier with LM741 operational amplifier(or uA741 op amp) is shown below.
In the above electrical drawing diagram, the lm741 supply voltage is a single supply of 12V. This single rail op amp amplifier design is made possible using the biasing resistors R5 and R6. In the tutorials Biasing LM741 for Single Supply with Split Resistor Biasing and Audio Amplifier design with uA741 op-amp we have explained how to bias uA741 op-amp(which is same as LM741 op amp) for single supply voltage. In the electronics schematic above, the first LM741 op amp is used for tone control and the second LM741 op amp along with push pull amplifier is used for amplifying the audio signal signal. The audio signal enters through the port shown as vin in the circuit diagram. The audio signal enters the tone control circuit via the coupling capacitor C1. Using the potentiometer RV2 and RV3 we can control the brass effect and treble effect on the audio. The resulting output signal is directly fed into the second op-amp. The second op-amp is an inverting amplifier. The output is this inverting amplifier is fed into the push pull amplifier which is made up of the NPN 2N3904 transistor and PNP 2N3906 transistor. The amplified audio signal from the push pull amplifier is then ac coupled to the 4Ohm speaker.
In this way we can design a 3W audio amplifier with LM741 operational amplifier and push pull amplifier. We can make an electret amplifier to pick up small signal as illustrated in the tutorial How to make electret microphone amplifier using LM358 and then connect that circuit to this audio amplifier circuit to create a complete audio signal acquisition and amplifying system.
See next How to design Powerful Audio Amplifier with LM741 op amp which illustrates another technique of designing powerful audio amplifier.
