Potent Audio Amplifier Circuit Using TDA7294

This is a design of Super Amplifier with tda7294 of the St micro eletronics, is possible to get potency of up to 100W in an only chip, for an unit stereo to use two same to that. That circuit is based on the datasheet of the ready to work with sources of strong signs, in case it is necessary it uses a pré-amplifier in the form of an op amp. This is the figure of the circuit;

That circuit type with integrated circuit is ideal for systems of involving sound. Because he is quite compact could use an independent amplifier for each one of the high speakers. In that way it can be to share the source dimensioned it is clear to support all the connected amplifiers. Oh you can remove a wave with that neighbor that bought a " home theater " of 1000W PMPO, and fear in saying that is an enormous potency, when in reality it will verify the real potency of the equipment it doesn't arrive nor to 10W RMS for channel. It already imagined a system of high active speakers with 80W.

Amplifier Biasing Circuit for Constant Gain with Temperature

This is a circuit for amplifier circuit. But, this circuit has function for biasing the amplifier in temperature system. This circuit is based on LM114. This is the figure of the circuit;


In the circuit, a differential amplifier with the current source biased by an LM113. Since the LM113 supplies a reference voltage equal to the energy band gap of silicon, the output current of the 2N2222 will vary as absolute temperature. This compensates the temperature sensitivity of the trans-conductance of the differential amplifier making the gain temperature stable. Further, the operating current is regulated against supply variations keeping the gain stable over a wide supply range. As shown, the gain will change less than two per cent over a b55§C to a125§C temperature range. Using the LM114A monolithic transistor and low drift metal film resistors, the amplifier will have less than 2 mV/§C voltage drift. Even lower drift may be obtained by unbalancing the collector load resistors to null out the initial offset. Drift under nulled condition will be typically less than 0.5 mV/§C.

[Schematic circuit source: National Semiconductor Notes]

Operational Amplifier Comparator Design

This is a design for comparator circuit. In operation the operational amplifier goes into positive or negative saturation dependent upon the input voltages. This is the figure of the design circuit.


Although op amps are widely used as comparator, special comparator chips are often used. These integrated circuits offer very fast switching times, well above those offered by most op-amps that are intended for more linear applications. Typical slew rates are in the region of several thousand volts per microsecond, although more often figures of propagation delay are quoted. A typical comparator circuit will have one of the inputs held at a given voltage. This may often be a potential divider from a supply or reference source. The other input is taken to the point to be sensed.

100W Guitar Amplifier Circuit

This is a circuit of the amplifier. This circuit is useful for electric guitar. This circuit is based on op amp TL072. This is the figure of the circuit.


The amp is rated at 100W into a 4 Ohms load, as this is typical of a "combo" type amp with two 8 Ohm speakers in parallel. For the really adventurous, 2 quad boxes and the amp head will provide 100W, but will be much louder than the twin. This is a common combination for guitarists, but it does make it hard for the sound guy to bring everything else up to the same level. This is a fully revised version of the original 100W guitar amp, and although there are a great many similarities, there are some substantial differences - so much so that a new version was warranted.

Super Bridge 120W Power Amplifier Circuit

This is a design for power amplifier. However, the amplifier is called Super Power Amp Bridge (BCL) 120W.


The main control circuit uses a BD249 transistor, IC TDA2030, TIP41, TIP31 or C1061 and BD250, TIP42, TIP32, A671. Here’s the schematic figure of the circuit.

2 Watt Amplifier Circuit

This is a design circuit for amplifier. This circuit is produces 2 Watt amp and made using discrete components. This is the figure of the circuit.


The amplifier operates in Class AB mode; the single 470R preset resistor, PR1 controls the quiescent current flowing through the BD139/140 complimentary output transistors. Adjustment here, is a trade-off between low distortion and low quiescent current. Typically, under quiescent conditions, current is about 15 mA rising to 150 mA with a 50 mV input signal. The circuit is not perfect, this amplifier does have a wide frequency response, low harmonic distortion about 1.5%, and is capable of driving an 8 ohm speaker to output levels of around 5 watts with slightly higher distortion. The circuit is DC biased so that the emitters of the BD139 and BD140 are at approximately half supply voltage, to allow for a maximum output voltage swing.

Servo Amplifier Using LM12

When making servo systems with a power op amp, there is a temptation to use it for frequency shaping to stabilize the servo loop. This is a circuit for implementation the servo amplifier. This is the figure of the circuit.


This motor/tachometer servo gives an output speed proportional to input voltage. A low-level op amp is used for frequency shaping while the power op amp provides current drive to the motor. Current drive eliminates loop phase shift due to motor inductance and makes high-performance servos easier to stabilize. [Circuit’s source: National Semiconductor Notes].

Sample Hold Circuit Using Op Amp

This is an implementation for sample hold circuit function that using op amp LM324. This is the figure of the circuit.


In this circuit, the input-to-output wiring has similar to standard configuration, but its operating principle is different. Key advantages include simplicity, no hold step, essentially zero gain error and operation from a single 5V supply. The sample-hold command pulse is applied to Q3, which turns on, causing current source transistor Q4's collector to go to ground potential. Amplifier A1 follows Q4's collector voltage and provides the circuit's output. When the sample-hold command pulse falls, Q4's collector drives a constant current into the 0.01 mF capacitor.

When the capacitor ramp voltage equals the circuit's input voltage, comparator C1 switches, causing Q2 to turn off the current source. At this point the collector voltage of Q4 sits at the circuit's input voltage. Q1 insures that the comparator will not self trigger if the input voltage increases during a ``hold'' interval. When a DC biased sine wave is applied to the circuit the sampled output is available at the circuit's output. The ramping action of the Q4 current source during the ``sample'' states is just visible in the output. [Schematic circuit source: National Semiconductor Notes].

The Basic of Op Amp

The op-amp is basically a differential amplifier having a large voltage gain, very high input impedance and low output impedance. The op-amp has a "inverting" or (-) input and "non-inverting" or (+) input and a single output. This is a form of op amp.


The inverting op-amp is connected using two resistors RA and RB such that the input signal is applied in series with RA and the output is connected back to the inverting input through RB. The non-inverting input is connected to the ground reference or the center tap of the dual polarity power supply. In operation, as the input signal moves positive, the output will move negative and visa versa. The amount of voltage change at the output relative to the input depends on the ratio of the two resistors RA and RB. As the input moves in one direction, the output will move in the opposite direction, so that the voltage at the inverting input remains constant or zero volts in this case.

The non-inverting amplifier is connected so that the input signal goes directly to the non-inverting input (+) and the input resistor RA is grounded. In this configuration, the input impedance as seen by the signal is much greater since the input will be following the applied signal and not held constant by the feedback current. As the signal moves in either direction, the output will follow in phase to maintain the inverting input at the same voltage as the input (+). The voltage gain is always more than 1 and can be worked out from Vgain = (1+ RB/RA).

Simple 8 Watt Audio Power Amplifier

This is an audio power amplifier circuit using only a single chip and few passive components, that you can build 8-14 Watt audio power amplifier using TDA2030 chip. This is very simple circuit. This is the figure of the circuit.


When you use 4 ohm speaker then you get 14 Watt output power, and around 8 Watt if you use 8 ohm loudspeaker. Make sure the 100n and 100u capacitor is wired as close as possible to the power input pin of the TDA 2030. You might wonder why we use 100uF and 100nf in parallel, if you think that we need 100.1uF capacitor then you’re wrong. All we need is just a capacitor around 100uF with small equivalent series inductance. At low frequency, the “relatively high” series inductance of the 100uF electrolytic capacitor can be neglected, but not for the high frequency. At high frequency, the TDA2030 is protected from instability by the 100nF capacitor, because the signals find the low inductance path here to bypass the fast power source variation.

500 mW Audio Amplifier Using 3 Transistors

This is a design circuit of audio amplifier that will be suitable for small battery powered devices, and the circuit is really simple. This tiny power amplifier use same typology as the more complicated version of discrete amplifier in our previous circuit, but with here is in the simplest form. This is the figure of the circuit.


This circuit is a very good start as a DIY amplifier because its simplicity. Since this audio amplifier process only audio signal (not a dc amplifier), both the input and the output are dc-blocked using capacitors. You can see 3.3 ohm resistors connected to the emitter of PNP-NPN transistor couple, and the purpose of this resistor is to stabilize the transistor gain, so the temperature change won’t affect the performance much. Any PNP-NPN transistor couple with identical performance that capable of handling 100mA collector current should be suitable to replace the final transistors. The voltage swing of the output will be 2 Volt at maximum (at 9V DC supply), so the current at 8 ohm speaker will be 0.25A, and the maximum power would be the 2V*0.25A=0.5Watts.

Accelerometer Amplifier Circuit

This is a circuit for accelerometer amplifier. This is a simple circuit. Precision accelerometer needs inverting mode amplifier since they are usually charge-output devices. This amplifier is convert charges into voltage output. The circuit below is an example of accelerometer with DC servo. This circuit built by IC LT1113.


The charge from the transducer is converted to a voltage by C1, which should equal the transducer capacitance plus the input capacitance of the op amp. The low frequency bandwidth of the amplifier will depend on the value of R1 • C1 (or R1 (1 + R2/R3) for a Tee network). The noise gain will be 1 + C1/CT. The time constant of the servo (1/R5C5) should be larger than the time constant of the amplifier (1/R1C1). [Schematic source: Linear Technology Application Notes]

Audio Amp Output Power Limiter Circuit

This is a simple peak limiter - performance is quite respectable, and it can be used with conventional amps using bipolar transistors, MOSFETs. The gain control element is a Light Dependent Resistor (LDR). These are blessed with a few very useful features for our purposes, one of which is low distortion even at quite high signal levels. This is the figure of the circuit.


The operation of the circuit is 10k resistor selected for the input, and although this is lower than I would like, many power amps have a relatively low input impedance and too much signal would be lost. The LDR simply shunts the signal to earth when it is illuminated. A single unit should control both channels of the power amp as shown. If only one channel is needed, then delete the components for "Right", including the associated light pipe. The value of R3 must be selected based on the amplifier power. For a 100W amp, a value of 1.8k is about right, but it is likely that a little experimentation will be needed. As a rough guide, the table below will be helpful, and it is probable that the value from the table will be OK. The idea is to limit the current through the LED to a sensible maximum.

100W Guitar Amplifier Circuit

The power amp circuit is built using TIP35/36C transistor, the output stage is deliberately massive overkill. The figure is show the circuit;


The principle work and specification guitar power amplifier is power transistors will have an easy time driving any load down to 4 ohms. If you don't use the PCB, you can use TO3 transistors for the output stage. MJ15003/4 transistors are very high power, and will run cooler because of the TO-3 casing (lower thermal resistance). Beware of counterfeits though! There are many other high power transistors that can be used, and the amp is quite tolerant of substitutes (as long as their ratings are at least equal to the devices shown). The PCB can accommodate Toshiba or Motorola 150W flat-pack power transistors with relative ease, if you wanted to go that way. TIP3055/2966 or MJE3055/2955 can also be used for light or ordinary duty.

50 Watt Amplifier Circuit

This is very rugged and reasonably power amplifier circuit that can be used for any audio applications. This is a good design for room audio. This circuit is based on transistor for the operation. This is the figure of the circuit.


The capacitor C1 controls low frequencies and capacitor C2 controls high frequencies. The circuit is basically a class B amplifier. The transistors 2N 3055 serves the function of driving the speaker. The other transistor functions as pre amplifiers for the driver stage. This is the basic scheme of the circuit. The maximum power level of amplifier can be set by adjusting the 500 Ohm POT connected with the BC107 transistor. The circuit can be powered using a 50 V DC power supply with 5A current rating. Power supply up to 60 V can be given to the circuit. Any way the power supply must be well regulated and filters to avoid noise. Volume control can be attained by connecting a 10 K POT in series to the input of the amplifier, but in the figure is not shown. Adjust the 500 ohm POT to obtain optimum performance. All capacitors must be rated higher than the supply voltage.

25W Hi-Fi Power Amplifier Circuit

25 W Hi-Fi power amplifier circuit is a one of simple design that’s build by transistor NPN and PNP. All devices are rated at 350V, with the power transistors having 230W power dissipation and the drivers are 50W. This supply voltage (approximately) may be obtained by using a 15-0-15V transformer. This figure is show the circuit and operation of the circuit.


The amp may also be operated at lower supply voltages for less power, but I do not recommend less than ±18V, which will provide around 15W into 8 ohms. The supply voltage should be a maximum of ±25V. This supply is easily obtained from a 20-0-20V transformer. All resistors should be 1/4W or 1/2W 1% metal film for lowest noise, with the exception of R9, R10 and R15 which should be 1/2W types, and R13, R14 must be 5W wire wound. The bootstrap capacitor (C5) needs to be rated at least 25V, but the other electrolyc can be any voltage you have available. The potentiometer (VR1) must be a multi turn type, as the current setting is critical. Each of these amps will require a 0.25°C/W heat sink (very large). Consider using a fan or even water cooling to keep temperatures as low as possible.

3 Transistor Audio Amp (80 mW)

This circuit is similar to the one above but uses positive feedback to get a little more amplitude to the speaker. The circuit is built from a small 5 transistor radio that uses a 25 ohm speaker. In the circuit above, the load resistor for the driver transistor is tied directly to the + supply. This is the figure of the circuit.


This circuit has a disadvantage in that as the output moves positive, the drop across the 470 ohm resistor decreases which reduces the base current to the top NPN transistor. Thus the output cannot move all the way to the + supply because there wouldn't be any voltage across the 470 resistor and no base current to the NPN transistor. This circuit corrects the problem somewhat and allows a larger voltage swing and probably more output power, but I don't know how much without doing a lot of testing. The output still won't move more than a couple volts using small transistors since the peak current won't be more than 100mA or so into a 25 ohm load. But it's an improvement over the other circuit above.