Circuit electrinic

LM3900 Audio Mixer Circuit

Audio mixer circuit consists of 4 four-channel amplifier (LM3900) two microphone inputs and two audio inputs are available directly online at this circuit. By adding the parallel with this circuit, you can increase the number of entries according to applications. Each input is connected to the inverting terminal of the LM3900.

The amplifier built in each section amplifies each audio input separately and fed to the output terminals. The output terminal of each channel is connected to a single output line with a resistance no greater than 680 and produces a mixture of audio output with low noise. This audio mixer circuit does not use a low impedance input sources to the mix of ideals. Capacitors C1 to C4 are decoupling capacitors corresponding channels. C5 is the decoupling capacitor production.

The existence of the peak indicator "Audio Peak Indicator" in an audio device is needed. Audio Peak indicator is a simple circuit to detect the peak level of audio signal. Audio Peak indicator circuit is built with duabuah transistor and LED indicator as peak level detection of audio signals.


The main function of a series of Audio Peak indicator is to determine the occurrence of the peak level of audio signal that is more than +4 dB, equivalent to 1.25 V rms. If the received audio signal Audio Peak Indicator more than +4 dB was the LEDs in series Peak Audio This indicator will light. Audio Peak indicator circuit is mounted on the output audio system.

We hope to form the reference materials in the manufacture of circuit pernagkat Audio Peak Indicators in the audio readers.

This audio amplifier project is a class AB audio power amplifier using a TDA2003 module power amplifier.It is simple to construct and has only a few outside parts. The module is designed with short circuit and thermal protection. It can drive lots as low as one.6 ohm and can delivering-over ten watts from a 16 V DC power supply. Figure one shows the TDA 2003 packaged and pin configuration.

The power supply ought to be well filtered to reduce mains hum, the on board capacitors alone are not adequate for this purpose but are necessary to make sure stability. Additional filtering is unnecessary if operating from a battery. If boards are used for stereo, you will need to double the size of the power supply.

The power supply necessary for is 8 - 18V DC at one Amp or more. Maximum output power will only be obtained with a power supply of greater than 1A at 16V DC, and using two ohm speakers (or two by four ohm speakers in parallel). However about 4W RMS can be obtained with a 12V DC, 1A supply in to a four ohm load.

The major circuitry is contained in the amplifier module. C1 is the-input coupling capacitor & blocks DC signal, so does C3 which is the output coupling capacitor, & C2which blocks DC from the feed back loop to the differential input. R2 & R3 set the level of feedback. C4 & R4 provide a high frequency load for stability where loudspeaker inductive reactant may become excessive. C5 & C6 provide power supply  filtering.

There ought to be no issues with the stability of the circuit, however in the event you do, make definite the power-supply filtering and leads are adequate. If necessary you might connect an RC compensation network-between IC pins two and four as in the knowledge sheet. Values for Cx of 22 - 33 nF and for Rx of 39 - 47 ohms,should be satisfactory whilst still maintaining satisfactory high frequency response.

The gain is equal to one + (R2/R3) = 101, or 40 dB, minus any input attenuation. You may reduce the-overall gain by increasing the worth of R3 in the event you are only able to make use of part of the potentiometer range as a volume control. For example, an R3 of ten ohms will give a gain of 23 (27dB).