Two-Way AF Amplifier LM4830 Circuit

Introduction

The Two-Way AF Amplifier LM4830 is a great choice for anyone looking for an easy way to give their audio system some extra oomph. It’s perfect for stereo, mono, and even bridged mono applications, letting you get the power and clarity you need from your speakers. The audio quality is top-notch, too – it boasts low distortion for tight bass and crystal-clear highs. And best of all, it’s easy to set up and use – with just a few simple connections, you can be rocking out in no time!

Circuit Diagram

of Two-Way AF Amplifier LM4830

**Two-Way AF Amplifier LM4830 Circuit (Figure-1)**

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Working Explanation

of Two-Way AF Amplifier LM4830

The LM4830, whose internal circuit is shown in Figure 1, is an integrated solution for two-way audio amplification. It contains a bridge-connected audio power amplifier capable of delivering 1 W of continuous average power to an 82 load with less than 1% total harmonic distortion (THD) operating from a 5 V power supply. The LM4830 can also deliver 100 mW into a single-ended 32 2 impedance (headset operation). There is a 30 dB attenuator in front of a bridged electricity amplifier with 6 dB of advantage. The attenuation is controlled through a 4-bit parallel digital control; with 15 steps of 2 dB each. The device also contains a microphone preamplifier with two selectable inputs. Mic is selected when HS is high and A1‚ is in single-ended mode. Mic2 is selected when HS is low and A1‚ is in bridged mode. This configuration is ideal for switching between the internal speaker and an external headset with a microphone.

The LM4830 also incorporates a buffer for driving capacitive loads. The device has a low-current shut-down mode making it suitable for low-power portable systems. In addition, it has internal thermal shutdown protection.

As shown in Figure 2, amplifier A1‚ can be used in one of two modes, bridged output or single-ended output. This also allows headphones to be driven single-ended. The output can be switched automatically from a bridged speaker drive to a single-ended headphone drive using a control pin in the headphone jack that is tied to the HS (headset) pin 3. When the voltage at the HS pin input changes from 0 V to 5 V, the Vo2 of the bridged amplifier output becomes high impedance. This allows the permanently connected internal speaker to be disabled when a headphone is plugged into the headphone socket. Output Vo1 then drives the headphone single-ended via output coupling capacitor Cc. This capacitor should be chosen to allow the full audio bandwidth to be amplified. Since Cc and R1‚ form a high-pass filter, the value of Cc must be high enough to allow frequencies down to 20 Hz to be amplified. The value is calculated from

Cc=1/[2€20RL]

where 16 ohms <- RL <- 600 ohms

The LD (load) pin 9 has two modes of operation. When this input is high, the power amplifier's attenuation control is in transparent mode, where the voltage on bits D0-D3 will cause the appropriate attenuation level to be latched and decoded within the IC. For normal attenuation, pin 9 should be at 5 V. When the pin is low, the power amplifier's attenuation control is locked out so that any change in the input bits will not cause a subsequent change in the amplifier's attenuation level.

The attenuation level is preset to -16 dB when the IC is first powered up, ensuring that pin 9 is low until the IC is fully biased. The preamplifier in this IC is intended for use as a microphone amplifier. Relying on the frequency reaction of the microphone, the preamplifier's response can be configured to suit the microphone. Capacitors may simply be used to limit the bandwidth of the frequency response of the preamplifier and improve the system's performance. Once the gain of the amplifier is chosen, the values of the resistors and capacitors may be determined with the following equations.

AVCL=1+Rf/Ri [2]
fLP=1/2rRfCi [3]
fHp=1/2rRfCi [4]

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Conclusion

The LM4830 is a highly versatile two-way audio amplifier that is ideal for almost any application. With its powerful output and wide range of controls, it can be used in any setup where volume control and a high-quality sound are desired. The input supports both balanced and unbalanced signals for maximum versatility. Its low distortion ensures that your signal remains as clean as possible, allowing for the potential of crystal-clear reproduction across the whole frequency spectrum. Moreover, its comprehensive protection circuitry protects from overloads and short circuits to make setup worry-free. Though affordable, the LM4830 is definitely an excellent choice for anyone looking to add quality audio amplification to their setup!