Diagram Diagosis

This is a one watt home stereo amplifier module project using the KA2209 IC from Samsung, which is equivalent to the TDA2822. It operates from 3-12V DC & will work from a battery since the dormant current drain is low. It requires no heat sink for normal use. The input & output are both ground referenced. Maximum output will be obtained with a 12V power supply & 8 ohm speaker, however it is suitable for driving headphones from a supply as low as 3V.

The Specifications of the home stereo amplifier :

D.C. input : 3 – 12 V at 200 – 500 mA max
Idle current : approx. 10 mA
Power output : > 1 Watt max. 4-8 ohms, 12V DC
Freq. Resp. : approx. 40 Hz to 200 kHz, 8 ohm, G=10
THD : < 1 % @ 750 mW, 4-8 ohm, 12V
Gain : approx. x10 (20 dB) OR x100 (40dB)
S/N ratio : > 80 dB, G = 20 dB
Sensitivity : < 300 mV, G = 20 dB
Input Impedance : approx. 10 k ohm

Description 

The gain is adjustable from ten to 100, i.e. twenty to 40 dB. Start with feedback resistors R1 and R3 of 1k ohm, this will give a gain of ten which ought to be adequate for most applications. In case you need more gain, you can remove resistors R1 and R3.This will give a gain of about 100, or 40 dB.The input attenuation can be adjusted by the potentiometer which can be used as a volume control. The IC gain ought to be kept as low as necessary to accomplish full output, with the in put potentiometer and your signal source at maximum.

Voltage Gain = 1+ R1/R2 = 1+R3/R4, however the maximum gain with no outside feedback is about 100, or 40dB. (GdB = 20log Gv)

This will keep the signal to noise ratio as high as feasible. Additional gain provided by the amplifier will reduce the S/N ratio by a similar amount, since the input noise figure is constant. Other values for R1 and R3 of between 1k and 10k ohm can be used if an intermediate gain level is necessary.

If driving a pair of headphones, you may also need a 100 ohm resistor in series with each output to reduce the output level, depending on headphone impedance & sensitivity. Make positive you start with the volume right down to check. Numerous headphones may be driven from the amplifier in the event you wish, since most headphones have at least 16 ohm impedance, or more often 32 ohm.

There are only a few outside parts, the IC contains most of the necessary circuitry. R1,R2 and R3,R4 are the feedback resistors. C1 provides power supply decoupling. C2 and C3 are the input coupling capacitors, which block any DC that might-be present on the inputs. C4,C5 block DC in the feed back circuit from the inverting inputs, and C6,C7 are the output coupling capacitors. C8, R5 and C9,R6 act as Nobel networks providing a high frequency load to maintain stability at frequencies where loud speaker inductive reactant may become excessive. The pot provides adjustable input level attenuation.

This electronic amplifier project is an IC amplifier module from ST Microelectronics, the TDA7294. It is intended for use as a prime quality audio classification AB amplifier in hi-fi softwares. Its low noise and distortion, broad bandwidth and good output present functionality, enabling it to produce excessive power in to each four ohm and 8 ohm heaps. Its each quick circuit and thermal protection.

With the addition of a handful of sections and the appropriate power provide, this module will deliver over 50W RMS in to four or eight ohms-with < 0.1% Total Harmonic Distortion (THD) and < 0.1% Inter-modulation Distortion (IMD). It can also be appropriate as a replacement power amp stage, or improve for loads of existing amplifiers of between 30W-50W, provided they have got the precise twin provide, & most do.

The Specifications of the digital amplifier project there are:

D.C. Input : 35V
Output energy : > 50W RMS, 4-8 ohm load.
Gain : 24 dB (30dB modification)
Input sensitivity : one.3V for 50W, 8 ohm
Signal-to-Noise ratio : > ninety five dB, (>105 dBA)
Frequency response : approx. 20Hz - 200kHz, �3 dB
Slew charge : > 10V/uS
THD : < 0.01%, 1W-40W, 1kHz
IMD : < zero.01%, 1W

The maximum provide voltage of the IC is +/- 40V. However the most dissipation of the IC can be exceeded even at a lower voltage. Therefore the provide voltage used require now not be over +/- 35V. This may additionally be developed the utilization of a 50V heart tapped-transformer, a diode bridge rated at 5A (min.) & a pair of electrolytic capacitors, as shown under. A lower secondary voltage transformer may even be used however the reduced DC voltage will lead to less energy output in to 8 ohms. You can still receive 50W in to four ohms with best 24V supply rails.

A 36V C.T. transformer offers you approx +/- 25V rails. The-mains transformer used must be feed at a most of 80VA. In the experience you require to run modules in a stereo amplifier you want to use a typical power supply. In this case the transformer ought to be charged at 150VA or higher.

Most of the circuitry is contained throughout the IC module. The enter sign is applied to pin three by capacitor C1 & low-pass filter R1/C2. The filter strengthens the coronary heart beat response & lend a hands stop RF indicators. The lower -3dB point is determined-by R2/C1 & R4/C3. This is set 20Hz for the values used. The higher -3dB point is over 200kHz. C7/C8 & C9/C10 provide further power provide filtering or decoupling.

R3/R4 are the feedback resistors. The achieve is 1+R3/R4 which is approx 16 times, or 24dB. In case you wish to elevate the enter sensitivity you can additionally alter the resistors to swimsuit. Changing R3 to 22k would elevate the acquire to 30dB and lower the enter-required for 50W in to eight ohm, to 0.6V, without affecting efficiency so much. In case you scale back the worth of R4 you are going to additionally need to raise C3 to maintain bass response, as this units the comments low frequency roll off.

Pin ten is a mute enter and pin 9 gives a standby mode. Muting ought to always happen earlier than standby mode is chosen. Connecting these pins completely to the provision rail ensures that the amplifier comes on right away on energy up. Any switch-on clicks may be eradicated by means of increasing the time constants of R5/C4 and R6/C5 if necessary.

Make definite that a heavy accountability heat-sink charged as a minimum one.4 stage C/W or higher is used.