electronics-amplifier tutorial

This amplifier has been simulated extensively, although I haven't built it yet. I am saving circuit this one for a time when I can spend good time building and making sure the wiring is going to be optimal. I am going to use this amp in a bi-amp situation with passive filters on the input. This will result in two amplifiers that amplify the highs and two amplifying the lows (for stereo) and thus I can achieve an effective power of 120W into each speaker.

To set the above amplifier up, set R1 to max and R12 to 0. After doing this successfully, power on the amplifier. Set R1 so that the measured output offset is between 30 and 100mV. Once set, adjust R12 slowly to achieve a quiescent current of around 120mA. Keep checking the quiescent current as the amp heats up as it might change due to voltage drop changes in the output devices caused by heat. The heatsinks should be 0.6K/W or less for two amplifiers.

A audio power amplifier circuit ideal for guitar or PA work or for use as a general-purpose subwoofer or hifi amplifier. Many people prefer Mosfets because of their legendary ruggedness. Altronics had a Mosfet amplifier module which produced 200W into a 4 Ohm load and so we decided to take a look it. It turned out to be based on the "Pro Series One" as mentioned above, although this version by Altronics has been derated and adapted to different Mosfets. It has a rated power output of 140W into 8W and 200W into 4 Ohm. Frequency response is within 1dB from 20Hz to 80kHz. Total harmonic distortion is rated at less than 0.1% up to full power and signal-to-noise ratio with respect to 200W is better than 100dB unweighted. 

This 200W MOSFET Amplifier  Circuit From http://electronics-diy.com/

This class A amplifier circuit requires a preamp as it hasn't got much gain. It requires big heat sinks and a large transformer and a great power supply and careful wiring, but in the end it is extremely simple and it sounds very good. The zener diode rejects any ripple coming from the power supply, But you still only want a ripple of 10mV max. The ripple reaching the input is amplified, so the zener gets rid of that, but whatever ripple there is will still reach the power stage.

Many early amplifiers operated in Class A, but as output powers rose above 10W the problems of heat dissipation and power supply design caused most manufacturers to turn to the simpler, more efficient Class B arrangements and to put up with the resulting drop in perceived output quality. Why Class A ? Because , when biased to class A, the transistors are always turned on, always ready to respond instantaneously to an input signal. Class B and Class AB output stages require a microsecond or more to turn on. The Class A operation permits cleaner operation under the high-current slewing conditions that occur when transient audio signal are fed difficult loads. His amplifier is basically simple, as can be seen from the block diagram.

This is a 60W power amplifier circuit based on 2N3055 transistor. The optimal supply voltage is around 50V, but this amp can work from 30 to 60V. As you can see, in this design the components have a big tolerance, so you can build it with almost any components that you can find at home. The output power transistors can be any NPN types, but do not use Darlington types.

Capacitor C1 regulates the low frequencies (bass), as the capacitance grows, the low frequencies are getting louder. Capacitor C2 regulates the higher frequencies (treble), as the capacitance grows, the higher frequencies are getting quieter.

This is a class B amplifier, this means, that a current must flow through the end transistors, even if there is no signal on the input. This current can be regulated with the 500 Ohm trimmer resistor. As this current increases, the sound of the amplifier is better, but output transistors are dispatching more heat. If the current is decreased, the transistors are dispatching less heat, but the sound quality is decreased.

Here is a simple subwoofer filter circuit that can be powered by a 12V DC. This circuit is very useful in automotive applications subwoofer. The circuit is a low pass filter whose pass frequency can be set between 60 to 160 Hz

The circuit is built around the TL072 dual op amp IC BIFET. Of the two operational amplifiers inside the chip, IC1A is wired as a buffer. The left and right audio inputs after mixing is fed to the input of the IC1A using the DPDT switch S1. Switch S1 is the phase control switch which can be used to make the subwoofer in phase with other speakers. When S1 is in position 2, 180 degree phase shift will be induced.POT R7 can be used for controlling the level. IC1B forms the low pass filter whose pass frequency can be controlled by adjusting the dual gang POT R13.

Here is a 120 watt stereo amplifier circuit using STK4241V. The MAX9710 a stereo audio power amplifier IC capable of delivering 2 x 120 Watts of out put to 8 Ohm loads. MAX9710 can be operated from a single ±32V to ±54V power supply.

This amplifier circuit is suitable for home power audio devices. The STK4241V amplifier specifications might lead you to believe that it can use supply voltages of up to ±78V. With zero input signal (and therefore no output) it might, but I don't recommend anything greater than ±45V if 8 ohm loads are expected, although ±54V will be fine if you can provide good heatsinking.

Here is a 3 Watt stereo amplifier circuit using MAX 7910 IC. The MAX9710 a stereo audio power amplifier IC capable of delivering 3Watts of out put to 4 Ohm loads. MAX9710 can be operated from a single 4.5V to 5.5V power supply , makes it ideal for hand held applications.The IC also features thermal overload protection.

This amplifier circuit is suitable for small power audio devices such as radio sets and portable CD players. 5 V DC power supply is used for powering the circuit. 6V battery with an IN 4007 diode series to the positive terminal of it can also be used instead of 5 V DC supply. The circuit will get a supply voltage approximately 5 V after 0.7 V voltage drop across diode.