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. No matter how much volume, an audio amp provides, there are still those who require even more. Resistor R3 controls the gain and Capacitor C3 couples the output to the speaker. The circuit in Figure 4 uses a LM IC amp and will provide up to 7 watts of output power for those who l380 to really experience their audio.

lm3800 In this circuit, R1 and C1 accomplish this task very well. The type sold by Radio Shack is the LM and is the one we used in this circuit.

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. The primary advantages of the LM series IC’s are higher output power, very low distortion and low external parts count.


It is little wonder that audio amp IC’s have replaced discrete transistors in most consumer km380 devices. The ln380 gain is only used when a very low input signal is to be amplified.

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 lm830 no IC socket if it is going to be operated at its full rated 2 watt output. 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 to 1.

This configuration will give us a gain of The main advantage to this IC is its 7 watt output which is why it has found its way into many inexpensive car radios. Input signals are normally fed to the non-inverting input while the inverting input is normally tied to ground.

Just lm38 regular op amps, audio amp IC’s have an inverting and non-inverting input.

It should be apparent now that audio amp IC’s have much to offer us in the way of low cost audio amp circuits. This IC offers low distortion and is a real bargain compared to discrete transistors.

In a previous article I discussed building audio amplifiers using discrete transistors. Perhaps the most unique feature is that it is available at any Radio Shack and can ln380 at voltages as low as 5 volts. My experiences with this IC revealed that it must be heat sinked at all times due to it’s high standby current.


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Because of l380 high gain of IC audio amps, it is highly recommended to isolate them from the power supply to prevent oscillations. 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. IC’s offer many advantages including high efficiency, high gain, low standby current, low component count, small size and ,of course, low cost.

By removing R2 and connecting C2 across pins 1 and 8, we can increase the gain to While many experimenters have stayed away from these little black mysteries, I am going to uncover some of their secrets and demonstrate how easy they are to use. For example, check out National Semiconductor at http: This IC can become quite warm and it’s important to get rid of excess heat through the pins.

It is important to understand that increasing the gain does not increase the output power. 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. There are many other audio amp IC’s available to us and data sheets can be easily obtained by searching the world wide web.