300 Watt MOSFET Real HI-FI Power Amplifier

Description:

My passion for excellence progressed over the past 40 years to developing sonically superior amplifiers to the highest possible standards, providing life like sound performance.

I am committed to sharing my experience of the RAS 300 with other enthusiasts sharing my passion for perfection.I designed this minimalist amplifier to be durable, simple to operate while offering high fidelity equivalent to the original sound source and would recommend partnering this amplifier only with other products of outstanding quality.

When I set out to design this amplifier, my aim was to create a product most suitable for the reproduction of complex music and speech signals. Although I placed high emphasis on electrical characteristics, the single most important requirement is achieving an audibly superior sound, vivid spatial imaging and superb tonal clarity.

Although the average listening level is normally less than 10 watts, my design approach was to create an amplifier with ample reserve power, but biasing it for class A at average listening levels reducing cross-over distortion to extremely low levels.

There is not one capacitor in the signal path, improved the accuracy of the tonal characteristics of instruments and voices significantly.
The RAS 300 has almost zero phase distortion far beyond the audio range resulting in perfect resolution and totally un-coloured sound.

Amplifier Specification:
Maximum Output: 240 watts rms into 8 Ohms, 380 watts rms into 4 Ohms
Audio Frequency Linearity: 20 Hz - 20 kHz (+0, -0.2 dB)
Closed Loop Gain: 32 dB
Hum and Noise: -90 dB (input short circuit)
Output Offset Voltage: Less than 13 mV (input short circuit)
Phase Linearity: Less than 13 0 (10 Hz - 20 kHz)
Harmonic Distortion: Less than 0.007% at rated power
IM Distortion: Less than .009% at maximum power

The amplifier consists of two completely separate monaural amplifiers each channel has its own power supply, resulting in zero inter-channel cross talk, a common phenomenon in amplifiers sharing the same power supply.

In order to obtain the full output power each supply transformer should be rated at 40VAC - 0 - 40VAC at 640VA. Unlike many designs relying on the reservoir capacitors to supply peak currents, I prefer to have the raw power available from the transformer resulting in much faster transients.

Although the RAS 300 specifications are moderate, when listening to it you will immediately experience the massive reserve power available and never have any cause of anxiety that something is going to give in that one would when driving many amplifiers loud.

You will hear nothing but reality with no distortion at any level and I guarantee that this amplifier will divulge the best qualities of any equipment connected to it.

Li-Po charger and balancer using LM317

This is a Li-Po charger and balancer project for R/C hobby.The charger circuit is based on the circuit of Electron head and all folks in the DIY electronics topic on the rcgroups.com.

Basic electronic components and supplies required for the Newbie Electronics

Essential components and accessories to start

The work on electronic projects is a good way to learn electronics and will be implemented depending on the project, a series of tools and electronic components can be requested. There are some basic elements and services that are needed in almost all electronic equipment and are a must.

The first electronic components that must be taken into account are resistances. You should have a good selection of resistancedifferent values in the range of a Mega-ohm to 10 ohms with a tolerance of 5%. Carbon film resistors are a good choice for small electronic projects. They are cheap and easily available both online and offline retailers.

Another important element that is necessary is for capacitors. Ceramic disc capacitors or electrolytic capacitors are both a good choice for beginners electronic design, and also a good choice would be needed in terms of values. (Lower voltage capacitors to50V) would probably suffice for most entry-level projects.

Signal diodes are also a good buy for electronic design and electronic components are used in a variety of projects. A package of 50, the silicon diodes 1N914 are a good choice, because switching and analog signals can be used.

The next component is electronic rectifier diodes, which are kept in power must be verified. Approximately 20 of these diodes at different values of a good number would startwith.

Transistor electronic components are considered later. PNP and NPN, which are the most common and widely available transistors would be needed. Recommend TO92 package for beginners.

The LEDs are a mixture of colors and rectangular and packages around a good addition. Most standard LEDs are now available through 3V to their power.

A switch is a component well in hand. Often used to the circuit switch on or off. If you useSelect Start, select a switch or button.

Depending on the circuits and integrated circuits, some projects would also be necessary. One of the most commonly used ICS is the 555-timer. Like all the above components, which are listed in a through hole and surface mount packages. Begins with the through the hole until you feel comfortable soldering small components.

Last but not least, some wire and coupling circuits are a must forElectronic projects. Depending on your project, how about a box design or accommodation? They protect the circuit from the elements and dust and can be fixed with screws.

Ready to get started with electronics? Now you have the basic elements together, find a good book on basic circuits. If you really have no experience with electronics, is not afraid of a book that is for children to achieve. The simple explanations and illustrations in these books you're ready to go tothe next phase of testing in a hurry!

Full-wave rectifiers description

– Half-wave rectifiers have some applications.

– However, full-wave rectifiers are the most commonly used ones for dc power supplies.

– A full-wave rectifier is exactly the same as the half-wave, but allows unidirectional current through the load during the entire sinusoidal cycle (as opposed to only half the cycle in the half-wave).

– Average value of output becomes twice that of the half wave rectifier output:

V_AVG = 2V_p/p

– There are two main types of full wave rectifiers:

i) Center-tapped full-wave rectifier.

– Two diodes connected to the secondary of a center-tapped transformer.

– Half of V_in shows up between the center tap and each secondary.

– At any point in time, only one of the diodes is forward biased.

– This allows for continuous conduction through load.

– Note that the peak inverse voltage (PIV) across D₂ is:

PIV = (V_p(sec)/2 – 0.7) – (-V_p(sec)/2)

= (V_p(sec)/2 + V_p(sec)/2 – 0.7)

= V_p(sec) – 0.7

– Since V_p(out) = V_p(sec)/2 – 0.7, we get:

V_p(sec) = 2V_p(out) + 1.4

– Thus, the PIV across each diode becomes:

PIV = 2V_p(out) + 0.7 V

ii) Bridge full-wave rectifier.

– When the input cycle is positive, diodes D₁ and D₂ are forward biased.

– When the input cycle is negative, diodes D₃ and D₄ are the ones conducing.

– The output voltage becomes:

V_p(out) = V_p(sec) – 1.4 V

– The reason we’d rather use a full bridge rectifier than a center-tap, is that the PIV is a lot smaller:

PIV = V_p(out) + 0.7 V

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Op-Amps having negative feedback

same input.

– The noninverting input is grounded.

– For finding the gain, let’s assume there is infinite impedance at the input (i.e. between the inverting and non-inverting inputs).

– Infinite input impedance implies zero current at the inverting input.

– If there is zero current through the input impedance, there is NO voltage drop between the inverting and noninverting inputs.

– Thus, the voltage at the inverting input is zero!

- The zero at the inverting input is referred to as virtual ground.

– Since there is no current at the inverting input, the current through R_i and the current through R_f are equal:

I_in = I_f.

– The voltage across R_i equals V_in because of virtual ground on the other side of the resistor. Therefore we have that

I_in = V_in/R_i.

– Also, the voltage across R_f equals –V_out, because of virtual ground. Therefore:

I_f = -V_out/R_f

– Since I_f = I_in, we get that:

-V_out/R_f = V_in/R_i

– Or, rearranging,

V_out/V_in = -R_f/R_i

– So,

A_cl(I) = -R_f/R_i

– Thus, the closed loop gain is independent of the op-amp’s internal open-loop gain.

– The negative feedback stabilizes the voltage gain.

– The negative sign indicates inversion.

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Characteristics and Parameters of Transistor

– The ratio of the dc collector current (I_C) to the dc base current (I_B) is the dc beta (b_DC).

– b_DC is called the gain of a transistor:

b_DC = I_C/I_B

– Typical values of b_DC range from less than 20 to 200 or higher.

– b_DC is usually designated as an equivalent hybrid (h) parameter:

h_FE = b_DC

– The ratio of the collector current (I_C) to the dc emitter current (I_E) is the dc alpha (a_DC). This is a less-used parameter than beta.

a_DC = I_C/I_E

– Typical values range from 0.95 to 0.99 or greater.

– a_DC is always less than 1.

– This is because I_C is always slightly less than I_E by the amount of I_B.

– From graph above we can see that there are 6 important parameters to be considered:

i) I_B: dc base current.

ii) I_E: dc emitter current.

iii) I_C: dc collector current.

iv) V_BE: dc voltage at base with respect to emitter.

v) V_CB: dc voltage at collector with respect to base.

vi) V_CE: dc voltage at collector with respect to emitter.

– V_BB forward-biases the BE junction.

– V_CC reverse-biases the BC junction.

– When the BE junction is forward biased, it is like a forward biased diode:

V_BE ? 0.7 V

– But it can be as high as 0.9 V (and is dependent on current). We will use 0.7 V from now on.

– Emitter is at ground. Thus the voltage across R_B is

V_R(B) = V_BB- V_BE

– Also

V_R(B) = I­_RR_B

– Or:

I­_RR_B = V_BB- V_BE

– Solving:

I_B = (V_BB- V_BE)/R_B

– Voltage at collector with respect to grounded emitter is:

V_CE = V_CC – V_R(C)

– Since drop across R_C is V_R(C) = I_CR_C the voltage at the collector is also:

V_CE = V_CC - I_CR_C

– Where I_C = b_DCI_B. Voltage across the reverse-biased collector-bias junction is

V_CB = V_CE - V_BE

Example:

Determine I_B, I_C, I_E, V_BE, V_CE, and V_CB in the following circuit. The transistor has b_DC 150.

Solution:

We know V_BE=0.7 V. Using the already known equations:

I_B = (V_BB- V_BE)/R_B

I_B = (5 – 0.7)/10kW = 430 mA

I_C = b_DCI_B = (150)( 430 mA) = 64.5 mA

I_E = I_C + I_B = 64.5 mA + 430 mA = 64.9 mA

Solving for V_CE and V_CB:

V_CE = V_CC – I_CR_C = 10V-(64.5mA)(100W) = 3.55 V

V_CB = V_CE – V_BE = 3.55 V – 0.7 V­ = 2.85 V

Since the collector is at higher potential than the base, the collector-base junction is reverse-biased.

– Changing the voltage supplies with variable voltage supplies in the circuit above, we can get the characteristic curves of the BJT.

– If we start at some positive V_BB and V_CC = 0 V, the BE junction and the BC junction are forward biased.

– In this case the base current is through the BE junction because of the low impedance path to ground, thus I_C is zero.

– When both junctions are forward-biased, the transistor is in the saturation region of operation.

– As V_CC is increase, V_CE gradually increases, as the I­_C increases (This is the steep slope linear region before the small-slope region).

– I_C increases as V_CC ­increase because V_CE remains less than 0.7 V due to the forward-biased base-collector junction.

– Ideally, when V_CE exceeds 0.7 V, the BC junction becomes reverse biased.

– Then, the transistor goes into the linear region of operation.

– When the BC junction is reverse-biased, I_C levels off and remains essentially constant for a given value of I_B as V_CE continues to increase.

– Actually, there is a slight increase in I_C, due to the widening of the BC collector depletion region, which results in fewer holes for recombination in the base, which causes a slight increase in b_DC.

– For the linear portion, the value of I­_C is calculated by:

I_C = b_DCI­_B

– When V_CE reaches a sufficiently large voltage, the reverse biased BC junction goes into breakdown.

– Thus, the collector current increases rapidly.

– A transistor should never be operated in this region.

– When I_B = 0, the transistor is in the cutoff region, although there is a small collector leakage current.

i) Cutoff

– As said before, when I_B = 0, transistor is in cutoff region.

– There is a small collector leakage current, I_­CEO.

– Normally it is neglected so that V_CE = V_CC.

– In cutoff, both the base-emitter and the base-collector junctions are reverse-biased.

ii) Saturation

– When BE junction becomes forward biased and the base current is increased, I_C also increase (I­_C – b_DCI_B) and V_CE decreases as a result of more drop across the collector resistor (V_CE = V_CC – I_CR_C).

– When V_CE reaches its saturation value, V_CE(sat), the BC junction becomes forward-biased and I_­C can increase no further even with a continued increase in I_B.

– At the point of saturation, I_C = b_DCI_B is no longer valid.

– V_CE(sat) for a transistor occurs somewhere below the knee of the collector curves.

– It is usually only a few tenths of a volt for silicon transistors.

iii) DC load line

– Cutoff and saturation can be illustrated by the use of a load line.

– Bottom of load line is at ideal cutoff (I_C = 0 and V_CE = V_CC).

– Top of load line is at saturation (I_C = I_C(sat) and V_CE = V_CE(sat))

– In between cutoff and saturation along the load line is the active region.

– More to come later.

Example

Determine whether or not the transistor in circuit below is in saturation. Assume V_CE(sat) = 0.2 V.

First determine I_C(sat).

I_C(sat) = (V_CC – V_CE(sat))/R_C

I_C(sat) =(10 V – 0.2V)/10kW = 9.8 mA

Now let’s determine whether I_B is large enough to produce I_C(sat).

I_B = (V_BB - V_BE)/R_B = (3 V – 0.7 V)/10kW = 0.23 mA

I_C = b_DCI_B = (50)(0.23 mA) = 11.5 mA

This shows that with the specified b_DC, this base current is capable of producing an I_C greater than I_C(sat). Thus, the transistor is saturated, and the collector current value of 11.5 mA is never reached. If you further increase I_­B, the collector current remains at its saturation value.

i) More on b_DC

– The b_DC of h_FE is not truly constant.

– It varies with collector current and with temperature.

– Keeping the junction temperature constant and increasing I_C causes b_DC to increase to a maximum.

– Further increase in I_C beyond this point causes b_DC to decrease.

– If I_C is held constant and temperature varies, b_DC changes directly with temperature.

– Transistor data specify b_DC at specific values. Normally the b_DC specified is the maximum value.

ii) Maximum transistor ratings

– Maximum ratings are given for collector-to-base voltage, collector-to-emitter voltage, emitter-to-base voltage, collector current, and power dissipation.

– The product V_CEI_C must not exceed P_D(max).

Example:

The transistor shown in the figure below has the following maximum ratings: P_D(max)=800 mW, V_CE(max) = 15 V, and I_C(max) = 100 mA. Determine the maximum value to which V_CC can be adjusted without exceeding a rating. Which rating would be exceeded first?

Solution:

First, find I_B, so that you can determine I_C.

I_­B = (V_BB – V_BE)/R_B = (5 V – 0.7 V)/22 kW = 195 mA

I_C = b_DCI_B = (100)(195 mA) = 19.5 mA

I_C is much less than I_C(max) and will not change with V_CC. It is determined only by I_B and b_DC.

The voltage drop across R_C is

V­_R(C) =I_CR_C = (19.5 mA)(1 kW) = 19.5 V

Now we can determine the value of V_CC when V_CE = V_CE(max) = 15 V.

V_R(C) = V_CC - V_CE

So,

V_CC(max) = V_CE(max) + V_R(C) = 15 V + 19.5V = 34.5 V

V_CC can be increased to 34.5 V, under the existing conditions, before V_CE(max) is exceeded. However, at this point it is not known whether or not P_D(max) has been exceeded:

P_D = V_CE(max)I_C = (15 V)(19.5 mA) = 293 mW

Since P_D(max) is 800 mW, it is not exceeded when V_CC = 34.5 V. So, V_CE(max) = 15 V is the limiting rating in this case. If the base current is removed, causing the transistor to turn off, V_CE(max) will be exceeded first because the entire supply voltage, V_CC, will be dropped across the transistor.

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Data Sheet of Diode

– Provides maximum ratings, electrical characteristics, mechanical data, graphs of parameters, etc. for electrical device in use.

– Several parameters are seen in a data sheet for diodes:

Maximum ratings

i) V_RRM: (Peak repetitive reverse voltage).

– Maximum reverse peak voltage that can be applied repetitively across the diode.

ii) V_R: (DC blocking voltage)

– Maximum reverse dc voltage that can be applied across the diode.

iii) V_RSM: (Nonrepetitive peak reverse voltage)

– Maximum reverse peak value of nonrepetitive voltage that can be applied across diode.

iv) I_O: (Average rectified forward current)

– Maximum average value of a 60Hz rectified forward current.

v) I_FSM: (Nonrepetitive peak surge current)

– Maximum peak value of nonrepetitive (one cycle) forward surge current.

– A graph for different temperatures is generally available.

vi) T_A:

– Ambient temperature.

vii) T_J:

– Operating junction temperature range.

viii) T_stg:

– Storage junction temperature range.

Electrical Characteristics

i) v_F: Instantaneous voltage across the forward-biased diode when forward current is 1 A at 25^oC. Shown generally shown by a graph.

ii) V_F(avg): Maximum forward voltage drop averaged over a full cycle.

iii) I_R: Maximum current when diode is reverse-biased.

iv) I_R(avg): Maximum reverse current averaged over one cycle (when reverse-biased with an ac voltage).

Offset Voltage Compensation and Bias Current

– Up until now we have mostly considered ideal op-amps in our discussion.

– We must, however, introduce some non-ideal characteristics, since they will have an effect on the op-amp operation.

– Transistors within the op-amp must be biased so that they have the correct values of base and collector currents and collector-to-emitter voltages.

– Ideal op-amp has no input current at its terminals.

– In practice, op-amps have small input bias currents (in the nA range).

– There is also a small offset voltage between the inputs.

Effect of an Input Bias Current

– Consider the inverting amplifier circuit shown below.

– If the input voltage is zero, there should be zero current coming into the inverting input of the op-amp.

– However, there is a small bias current, I₁, that goes through R_f.

– This current creates a voltage at the output equal to I₁R_f.

– This is the error voltage.

– The same voltage will be seen at the output of a noninverting amplifier.

– If we look at the voltage follower circuit shown below, it is easy to see that the output error voltage is –I₁R_s.

Bias current compensation in a voltage-follower

– Somehow we need to compensate for the error voltage due to the bias currents.

– In a voltage follower it is enough to add a resistor, R_f, equal to the source resistance, R_s, in the feedback path.

– The voltage drop created by I₁across the added resistor subtracts from the –I₂R₂ output error voltage.

– If I₁ = I₂, then the output voltage is zero.

– Usually they are not equal, but even then the output voltage error is reduced, since the input offset current, I_OS, is less than I₂:

V­_OUT(error) = |I₁ – I₂|R_s = I_OSR_s

Bias current compensation in other op-amp configurations

– In a noninverting amplifier we add a resistor R_c.

– The compensating resistor value equals the parallel combination of R_i and R_­f.

– The input creates a voltage drop across R_c that offsets the voltage across the combination or R_f and R_i.

– Thus, the output is reduced.

– The same is done for the inverting amplifier.

Input offset voltage compensation

– The output voltage of an op-amp when the differential input is zero should be also zero.

– However, due to unavoidable internal imbalances and due to non-zero bias currents, a small voltage, V_IO, is seen between the terminals.

– ICs provide a means to compensate for this.

– This is generally done by connecting an external potentiometer to pins designated with Offset Null.

– With zero input voltage, the output is set to zero by adjusting the potentiometer.

– The pinout for the 741 op-amp (the most common op-amp IC) is shown next.

The LM35 device offers an ideal way to accurately measure the temperature

If you consider that a temperature sensor-project based on the easiest way to do this, a sensor for the temperature coefficient of the diode. This coefficient is a measure of how a junction diode responds to temperature and knows all the electronics that is-2.1mV per degree centigrade.

There are two problems with the use directly:

1. It's Going Down.

2. It is very small and uncomfortable to read.

3. Notcalibrated.

Direction

Of course, with operational amplifiers, you can solve these problems and the first for the problem, you can create a REG, in its reverse mode, so now you have an output ranging from 2.1mV per degree Celsius to be used .

Output Size

For the second problem would be much easier to use if the actual return could be read directly with a voltmeter for example 25 degrees Celsius of 250mV is much easier to read than 52.5mV.(52.5/2.1 = 25).

What we really want is one output, the increase in linear 10mV increments for each grade by grade is a good value for comfortable reading on a voltmeter.

You can do it with an ADC with a gain of 4.76191.

If you're an engineer who immediately see the problem - is lagging far behind the 4 decimal places, which means that you will need super precision resistors to get the job done. Of course, you can use a standard 4.7k resistance to about oneapproximate result, but for measurements of temperature, you really want an accurate production.

For example, with a gain of 4.7 to 25 degrees results in a Celsuis performance 246.75mV say that it is already in error by half a degree.

Calibration

As with all circuits discrete diodes have the device at a temperature of note, for example, by subtracting the diode in very cold water or calibrate the diode voltage corresponding with a different startREG.

Comfortable CI: LM35

While you can do all these different actions and to make a discrete version of a project, a very comfortable temperature measurement IC is not all for you.

This is the LM35 temperature IC to solve all these problems:

1. Produces an output that increases with temperature.

2. Increase generate output 10mV per degree centigrade.

3. It is fully calibrated.

Which methodUse either project specific or a simple way to measure IC, the output is used to feed them the ADC input of a microcontroller.

You can then use the microcontroller, a series of temperature readings over a period that you want at any time interval you need to do so it is easy to make a temperature of draft registration.

3. Grade Science Fair Projects and Ideas

3. Class Science Fair Projects are a lot of fun, because children of this age are eager to explore the world around them and find out how things work. They are always ready to find the answer to the question "What happens if I know ..." and therefore are likely to come with many different experiments you'd like to try. It can be difficult to decide on one!

At this age, have a short attention, however, that the projects in a simple, fun and pretty short.There are many, many different project ideas for this age group, for example, that make all the boys in her class the same size hands and feet the same size as everyone else? You can search by drawing the hands of other children and standing on a piece of paper or other similar systems.

They were a test to see if the mascara is truly waterproof raincoat. To do so would be a few brands waterproof mascara, a piece of paper and a bit 'of water if necessary. Simply put mascara ona sheet of paper, and rinse it under water to see what happens.

Another fun science project for class 3 would be to see if turning raw eggs and hard boiled eggs, the same number of times. Of course they would need help with an adult, with this for the eggs to boil, and then simply rotate each egg and record the results. There are many large Class 3 Scientific projects out there, it's just a matter of finding one, who are interested.

2-20 Watt Stereo Audio Power Amplifier by LM1875

Description:

Here is a reliably high sound quality audio power amplifier project based on the National Semiconductor’s LM1875 IC. The circuit that we give is a similar form of the application circuit in the datasheet that NS provides. It is really easy to build and low cost. The voltage gain of the each monolithic channel is 27dB but you can change this value by adjusting the resistors at the feedback path that connects the pin-2 and pin-4.

The supply voltage for the maximum power output (25 Watts) is +/- 25V. It mustn’t exceed +/- 30V at any time. We recommend you to use metal film resistors and electrolytic capacitors that are rated at 50V.

Read More Source: http://sound.westhost.com/project72.htm

LM3886 Power Sub Woofer Amplifier

Self switching Power Supply

One of the main features of the regulated power supply circuit being presented is that though fixed-voltage regulator LM7805 is used in the circuit, its output voltage is variable. This is achieved by connecting a potentiometer between common terminal of regulator IC and ground. For every 100-ohm increment in the in-circuit value of the resistance of potentiometer VR1, the output voltage increases by 1 volt. Thus, the output varies from 3.7V to 8.7V (taking into account 1.3-volt drop across diodes D1 and D2).
Another important feature of the supply is that it switches itself off when no load is connected across its output terminals. This is achieved with the help of transistors T1 and T2, diodes D1 and D2, and capacitor C2. When a load is connected at the output, potential drop across diodes D1 and D2 (approximately 1.3V) is sufficient for transistors T2 and T1 to conduct. As a result, the relay gets energised and remains in that state as long as the load remains connected. At the same time, capacitor C2 gets charged to around 7-8 volt potential through transistor T2. But when the load is disconnected, transistor T2 is cut off. However, capacitor C2 is still charged and it starts discharging through base of transistor T1. After some time (which is basically determined by value of C2), relay RL1 is de-energised, which switches off the mains input to primary of transformer X1. To resume the power again, switch S1 should be pressed momentarily. Higher the value of capacitor C2, more will be the delay in switching off the power supply on disconnection of the load, and vice versa.
Though in the prototype a transformer with a secondary voltage of 12V-0V, 250mA was used, it can nevertheless be changed as per user’s requirement (up to 30V maximum. and 1-ampere current rating). For drawing more than 300mA current, the regulator IC must be fitted with a small heat sink over a mica insulator. When the transformer’s secondary voltage increases beyond 12 volts (RMS), potentiometer VR1 must be redimensioned. Also, the relay voltage rating should be redetermined.

DMOS mono amplifier 100W with TDA7294

You have purchased construction quality Hi-Fi amplifier operating in class AB. Thanks to its small size, protected against short circuit on the output, overheating and the possibility of attachment directly to the metal box will find its use in many places. Whether it is ozvučování concerts or fitting into the estate, such as the guitar. Jet shocks to the speaker when you turn on and off the amplifiers in this circuit is minimal. Watch out, the device operates with a relatively large currents and tensions. Do not construction in both hands, it is under stress.

Wiring diagram

This is the recommended involvement of the circuit TDA7294 company SGS Thomson. All material lies in the ICs. How preamplifier, as well as end-stage DMOS, MUTE function, STBY, protection against overheating, short circuit on the output. Capacitors C6 and C8 are the filter and cover the tip of sampling, it is not necessary dimension to the exercise of the power supply, which will benefit permanently. For example, the sound of drums in the strike will cause many times higher collection of resources than the median value. These capacitors in particular avoiding the emergence of bias, resulting in the strong signals as a result of excessive voltage decreases in resources.

Capacitors C7 and C9 improve the stability of the RF amplifiers zákmitům. Resistor R3 between 2 and 14 outlets providing negative feedback as DC (stabilizes the working point, respectively. DC voltage at the output), and together with R2 alternating link. It determines the overall gain, reduces distortion and balances characteristic frequency amplifiers. Here listed are recommended by the manufacturer, to achieve the best parameters, but if necessary, within certain limits vary. For example, if you need to limit the performance of amplifiers because of a smaller cooler or have loudspeaker systems for smaller performances and to prevent their destruction, just increase R2 value, or reducing the value of R3 reduce gain. DC capacitor C1 separates from the amplifier input signal sources that had no direct working point amplifiers. Through switches and resistors R4 and R5 will bring tension to STBY (Stand By) and MUTE. C3 and C4 allow continuous activation and deactivation of these functions.

Construction

Place PCB PT002 (supplied with green nepájivou mask, printing components and drilling machine CNC), which is designed to be received from the external environment as far as possible to interference and match proudovému load. Therefore, the power and output connections as broad as possible. It is used cuprex FR4 with 35μm strong copper foil.

Order mounting: 1st capacitors, resistors 2nd MKT 5 mm 3rd terminals 4th switches 5th other capacitors 6th TDA7294

DA7294 pájejte last try, and the shortest possible time. Pájejte conscientiously so as to avoid cold couplings. Across-the-board connection through the large currents, only high-quality construction makes the minimum risk. Connection output signal is limited in one place. There is no pattern nanesena nepájivá. At this point apply a drop of tin to improve the conductivity and the possibility of a larger load without the risk of burning the journey. You have two ways to complete construction:

A: not intend to use the features STBY and MUTE. Then switch SW1 and 2 zapájíte directly into the joints and their situation will be running for the top amplifiers. In this connection, which is based directly from the diagram, you can only disable the function, rather than immediately turn on. Can be activated only by switching radio before switching on the amplifier and the spent condensers. Use: for animation, when we want to measure sleep donation but later exploit these features.
B: Do you intend to use the features. In this case, the switch will not be soldered into the joints (logically, not because of any change to open the box or combo), but lead out through the wires (included). In this engagement - see the picture, are optional features, the possibility of activation and deactivation at any time during the operation. SW2 se zapojuje stejně jako SW1. SW2 is involved as well as SW1. When the two structures is necessary in the terminals MT and SB bring positive supply voltage.

The last thing it should be in construction to make, is attached aluminum profile, which allows direct attachment to the metal skříním and easier attachment coolers. The body must be first navrtat - in the middle of a hole for attaching IO, d = 3mm, with navrtáním d = 6mm in the rear of one quarter of units for flush screw head to the back wall to enclose the entire area to chladícímu element. Then, just as necessary drill holes on the edges of the profile. And again, for example, d = 3 mm, the zavrtáním d = 6mm in one quarter (2.5 mm) of its thickness. See the real picture above. Adequate evacuation of heat from ICs provide aluminum plate on the surface 0,75 dm ^{2 and} a thickness of 5 mm. There are screws and nuts to facilitate the handling of the plate mounted amplifier in the animation. Thermal resistance of external cooler: 0.8 K / W.

It's not required but is symmetrical source of tension, there is attached recommended tested and well-functioning wiring diagram. Toroidal transformer best, at least 150W, optimally 2x25V/200W. Policies to protect the source and amplifier from destruction. LEDs indicate the tension on both branches. Once unlit, for example, LED1, you know, it is burned fuse, or other problem in a positive power. Capacitors C1 and C5 are the filter. The minimum recommended amount 5mF, but higher values can only benefit - less badboy. Then it depends on how much you're willing to finance investment in resources and its quality, because comparatively, with a capacity of capacitors is growing, as well as their price. In the greater interest we are willing to source with the PCB and all parts sold as a kit.

Revival

Equipment is not necessary to recover. When good design, sufficient resources sized works on the first engagement. In any case, do not amplifier without the cooler. Threatened with destruction or degradation of the quality of reproduction.

R1, R3, R4 R1, R3, R4	22k	C1 C1	MKT 220 - 470n MKT 220 - 470n	C6, C8 C6, C8	1000m/50V
R2 R2	680	C2, C5 C2, C5	22m/50V	C7, C9 C7, C9	MKT 100n/63V MKT 100n/63V
R5 R5	10k	C3, C4 C3, C4	10m/50V	IO1 IO1	TDA7294

Tags: Schematics, Electronic Circuit, Mosfet Amplifier, Audio Amplifier, Car Audio, Power Amplifier, Power Supply