Analogue Sound System Circuit Description - Essay Example

? Analogue Sound System Circuit Analogue Sound System Circuit There has been the need to make improvements regarding sound systems such as in terms of efficiency and power gains. The solution is to come up with analogue sound system. The diagram is a representation of a typical analogue sound system. It is a constituent of various components. Figure 1: analogue sound system circuit The design and components of the system circuit is described as follows. The Mixer The mixer is a constituent of the music and speech signals. The resultant signal is channelled into the powered amplifier. The role of the power amplifier is to drive the loudspeaker. The circuit is designed such that the mixer contains a gain that can be varied, depending on the desirability of the required volumes. In addition, there should be the allowance for the volume of one channel to be controlled separately from another. This enhances the quality of sound as this enables one to have balance between the two channels. In this regard, the presented diagram consists of a set of two inputs; the speech and music. In this case, the speech voltage controls the music voltage. The operation of the circuit project only requires that the two signals are combined while the current should be adjusted to be adequate to make the speakers work effectively. It is expectable that in the cases where speech signal is lacking, the music voltage from the difference amplifier is about 1V. In the cases where the speech signal is peak, the voltage is expected to be at the minimum level, at around 0.17V. In this regard, mixing the speech and music amplifier creates the allowance to have the music volume by varying the voltage of the speech signal. Even so, the mixer’s output does not have the power capacity of driving the speakers. In this regard, it is expectable that when the amplitude of the mixer’s input is raised by a gain of well over 10 units, as well as utilizing the class B type of amplifier so that adequate current can be generated, the circuit would work successfully. The amplifier is connected to the speakers. About Power amplifiers Conventionally, most power amplifiers make use of the output stage, in the cases where a single transistor handles a half of the waveform signals and this is regardless of whether the half is negative or positive. This operation is often labelled as the push-pull. Its efficiency is unquestionable, considering that only minimal current flows when music signal is lacking. Furthermore, this comes with the implication that the compact power supply may be the only most essential component; hence it cost-effectiveness to the manufacturer. For the user, the resultant amplifier is relatively small in size, efficient and cheap. The power amplifier functions to deliver power, a product of load current and voltage. Power= IV I ~ Current V ~ Voltage In the basic sense, a power amplifier shares a lot of commonalities with the voltage amplifier. The only difference between the two is that in the power amplifier, the resistance of the load that is connected to the output is relatively low, for instance, a loudspeaker consisting of 7 ohms that triggers the flow of high current through the transistor’s collector. In consideration to the high currents that flow through the loads, it is imperative that the output transistors that are applied in the amplification of power should have high resistance. There are two categories of amplifiers that could be used; A-type and B-type amplifiers. The A-type amplifiers are those in which the output current assumes the inputs’ full cycle, creating the allowance of the transistors to be forward-biased through the input cycles, without switching off. The following is an extract of the diagram for the A-type amplifier. Figure 1: A-type Amplifier On the other hand, the B-type amplifier is that which is designed to improve the energy of efficiency of the A-type amplifier, ensuring for the reduction of the amount of heat loss? Besides, its signal assumes a half cycle. The diagram below is a representation of the B-type amplifier. Figure 2: B-type amplifier The functioning increases the efficiency, as well as the gains of the DC power source. Nevertheless, the inherent disadvantage of this is the production of the cross-over distortion while the two signals are recombined at the output. In the cases where the input signal is lacking, the values of quiescent transistor collector is determined by the base bias of the cut-off points. The most common way in which the distortions can be curbed in this category of amplifiers is by have all the transistors biased at the points that lie slightly above the cut of points. This results to the creation of the AV-type amplifier. AB-type amplifiers The AB-type of amplifiers refers to the amplifiers that ape both the functioning of the A-type and B-type. These are often the B-type category, only that that there is the allowance for the current to flow at the quiescent regions and eliminates the existence of the cross-over distortion. The AB-type of base-emitter’s voltage should be more than the turn-on voltages for the transistors to work. To achieve this, a pair of the biasing diodes are placed the terminals at the base so that the voltage dissipated to the transistors equals the drop of voltage at the diode. The fact that the voltage of the diode is biased implies that the pair of transistors continues to conduct current even when the input signal is lacking. This feature creates the allowance for the transistors to function in the normal way to overcome distortions inherent in B-type amplifiers. This way, the A-type linearity and B-type efficiency is provided based on the requirements. This also creates the allowance to choose the points of bias with flexibility. The diagram below is a representation of the AB-type of amplifier. Average power is denoted is about 70 percent Figure 4 Power transistors There are various categories of power transistors that find applicability in the circuit, all of which have varied characteristics. For instance, BD135/6 and TIP41C/42C are some of the applicable transistors with different qualities. These classes of transistors have a relatively low gains but large silicon areas and thus require checking of their operating conditions. There gain increases with temperatures. Transistors Q1 and Q3 belong to the same class of gains. Bias current The biasing circuit is utilized for the production of the current denoted as Ib, which is the allowed to flow through the Vbe multiplier. The pnp transistors are applied. VBE Multiplier Since the usage of diodes in biasing circuit gives rise to problem regards to thermal stability and linearity, another efficient biasing circuit would be the Vbe multiplier. As can be seen on the figure above, it is made of two resistors, R1 and R2 connected in series with each other and with an npn transistor. Protection of Short circuit is done by adding another transistor to the circuit as shown below. Read More