4 Aug Hello everyone! I hope you all will be absolutely fine and having fun. Today, I am going to share my knowledge about Introduction to LM The LM is a power audio amplifier for consumer applica- tions. In order to hold system cost to a minimum, gain is internally fixed at 34 dB. A unique input. The LM is a power audio amplifier for consumer applica- tion In order to hold system cost to a minimum gain is internally fixed at 34 dB A unique input stage.

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Output capacitor coupling is mandatory in just about all IC audio amp designs. It should be apparent now that audio amp IC’s have much to offer us in the way of low cost audio amp circuits.

My experiences with this IC revealed that it must be heat sinked at all times due to it’s high standby current. This IC can become quite warm and it’s important to get rid of excess heat through the pins. Input signals are normally fed to the non-inverting input while the inverting input is normally tied to ground. While it is possible to build good audio amplifiers from discrete transistors, they are no match for the many audio amp IC’s available to us.

If you plan to use this IC keep all components as close as possible to the IC and be certain that your power source can supply up lm308 1. Resistor R3 controls the gain lm38 Capacitor C3 couples the output to pm380 speaker.


The main ml380 to this IC is its 7 watt output which is why it has found its way into many inexpensive car radios. The circuit in Figure 4 uses a LM IC amp and will provide up to 7 watts of output power for those who want to really experience their audio.

By removing R2 and connecting C2 across pins 1 and 8, we can increase the gain to Back to Projects Page!

The LM comes in an 8 pin package and its basic circuit is virtually identical to the LM except for the different pin out. Perhaps the most unique feature is that it is lm3380 at any Radio Shack and can operate at voltages as low as 5 volts.

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Almost all of the major IC manufacturers now offer their data sheets to be downloaded free at their web sites. Experience has shown the LM should be soldered directly to the circuit board no IC socket if it is going to be operated at its full rated 2 watt output.

The type sold by Radio Shack is the LM and is the one we used in this circuit. It is little wonder that audio amp IC’s have replaced discrete transistors in most consumer electronic devices.

There are many other audio amp IC’s available to us and data sheets can be easily obtained by searching the world wide web. Just like regular op amps, audio amp IC’s have an inverting and non-inverting input.


This configuration will give us a gain of This IC offers low distortion and is a real bargain compared to discrete transistors. For example, check out National Semiconductor at http: It is important to understand that increasing the gain does not increase the output power. In a previous article I discussed building audio amplifiers using discrete transistors.

In this circuit, Lm3880 and C1 accomplish this task very well. IC’s offer many advantages including high efficiency, high gain, low standby current, low component count, small size and ,of course, low cost. The primary advantages of the LM series IC’s are higher output power, very low distortion and low external parts count. Because of the high gain of IC audio amps, it is highly recommended to isolate them from the power supply to prevent oscillations.

No matter how much volume, an audio amp provides, there are still l,380 who require even more. The LM comes in a 14 pin package and pins 3,4,5,10,11 and 13 are connected to ground to act as a heat sink. While many experimenters have stayed lj380 from these little black mysteries, I am going to uncover some of their secrets and demonstrate how easy they are to use. The increased gain is only used when a very low input signal is to be amplified.