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transients that are generated by the switching of the inverter transistors. Here’s the figure of the design circuit;

Developed as a compact low-cost solution for just this type of design problem, the HCPL-7800 High CMR Isolation Amplifier allows designers to sense current in extremely noisy environments while maintaining excellent gain and off set accuracy. It exhibits outstanding stability over both time and temperature, as well as unequaled common-mode transient noise rejection (CMR). To achieve such a high level of performance, the HCPL) analog-to-digital converter (-7800 combines several different technologies, including a state-of-the-art sigma-delta (ADCm standard-cell), chopper-stabilized internal amplifiers, a fully differential circuit topology fabricated on a 1  CMOS process, an edge-triggered level-sensitive data encoder/decoder circuit, a high-efficiency, high-speed AlGaAs LED, an advanced photo-detector noise shield, and an efficient “light-pipe” packaging technology. The HCPL-7800 is available in a small 8-pin DIP package, making it the world’s smallest isolation amplifier.

A simple
stereo audio amplifier is built around two 7905 negative-voltage
regulators (IC1 and IC2) and a few discrete components. The circuit
will also work with other 79XX regulators if appropriate power supply
is used. Regulator IC 7905 works as an amplifier for the voltages
applied to common pin2 (Ground or GND). Also check the LM317 audio
amplifier, another interesting circuit.The minimal voltage drop over the
standard 7905 is around 2V and it depends on the output current.
Feedback resistors in the IC set the gain of the channel internally.
The amplifier is a class-A audio amplifier. The minimal applicable
value of R3 for the regulator 7905 is 8.2 to 10 ohms per 5W.

7905 1 Watt Audio Amplifier Schematic

If
the required output current for LS1 is below 100 mA, the value of
resistor R3 can be 33 to 51 ohms per watt. The circuit works with any
load resistance (R3 in parallel with LS1 as the load) under the
condition that the regulator is not overloaded with current and power
dissipation. However, it is preferable to use a loudspeaker with a high
resistance (8 ohms, 16 ohms or more). The amplifier works well with
low-impedance headphones having a resistance of 24 to 32 ohms. The
voltage difference between the ground pin of 7905 and the output pin is
fixed internally.
S2 is the on/off switch. Switch S1 is for
mono/stereo selection. When switch S1 is closed, the amplifier works as
a two-way mono amplifier. If S1 is open, the amplifier works as a
stereo amplifier. If no input signal is applied, the DC voltage on the
output of the regulator 7905 should be around –5V, which depends to
some extent on the value of VR1. The maximum output current of 7905 can
be up to 1A and the maximum power dissipation is up to 15W. Mount the
regulator IC 7905 on a heat-sink with

Finding the best amplifier for your auto sound system can be a lot easier if you take the time ahead of time to learn what you need and what will work best with the sound system youve selected for your car, truck, or SUV. It helps to understand what an amplifier does in order to purchase the one that will best suit your needs. An amplifier takes a small sound, adds a little boost of its own, and then turns it into a big sound. The more power your amplifier has, the better quality of sound it will provide. An underpowered amplifier will have a thin, tinny sound that is rather unattractive in an auto sound system, or any other sound system for that matter.

You should also take care to remember that the power rating of an amplifier is the maximum power it is capable of expending not the amount that it will regularly use. The RMS rating of an amplifier is a good indication of its power output. One thing that is important to remember is that you should never buy an amplifier based on the maximum output or RMS rating. This number is more often than not incredibly misleading. If a driving, thumping bass beat is important to you then you should make sure that your amplifier has a bass boost button. This button will or switch will give a little bit of a boost to your bass. Its something I can pass on by many bass lovers cannot live without. Not all amplifiers have this so choose wisely and according to your preferences.

When it comes to amplifiers there are essentially four major classes (there are other classes but they are not all that common so I will not dwell on defining them) that represent the quality of sound you should expect from the system.

1) A. This class has a great output of quality sound but wastes huge amounts of energy in the process of creating that wonderful sound.

2) B. This class is slightly better than A as far as it wastes less energy and slightly worse as it produces a somewhat inferior quality of sound.

3) A/B. This resembles either A or B as far as sound and energy waste goes depending on the volume. Lower volumes will utilize the class A qualities of the amplifier while louder volumes are more in keeping with class B.

4) D. This class is primarily decent for producing a good bass sound and little else. The quality of sound and amount of energy wasted are both only moderate and neither are very impressive.

Of course this is the bare bones run through of the very basic amplifier basics. Another thing to note is that many people simply refer to amplifiers as amps rather than saying the entire word. Its slang but its so common that no one will blink if you do it. In fact you are far more likely to get funny looks for calling it an amplifier. Regardless of the small talk an amplifier isnt the end all be all of an auto sound system. It is only important if you feel it is important and many sound systems work splendidly without an extra amplifier to confuse the process and raise the price.

Whenever you decide to buy a new auto sound system for your car, truck, or SUV there is a moment of exhilaration and excitement as this is often a decision youve mulled over for quite a while rather than a spur of the moment decision. This exhilaration is promptly followed by a moment of complete and utter fear, as most of us have no clue what we really need. Hopefully, this has helped you decide whether or not you will need an amplifier and if you will, perhaps you can make a more educated and informed decision as to the type of amp you need.

Amplifier circuit with IC STK is tough and good quality. In this article an amplifier circuit with IC STK another base. Power "Amplifier 200Watt By STK4050" is an audio amplifier of the STK family with 200Watt power. To create a power amplifier with the STK4050 IC is not require many external components.

Power Amplifier uses symmetric 30Volt power supply system. Power Amplifier With this STK4050 can reproduce the power 200 Watts at 8 Ohm load spaker. In making Power Amplifier 200Watt With this STK4050 do not forget to provide adequate heat sink for the IC STK 4050 in order to avoid overheating.

This circuit is for amplifier 80 mW uses positive feedback to get a little more amplitude to the speaker. This is a simple design for a small amplifier. This 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 wouldnt be any voltage across the 470 resistor and no base current to the NPN transistor. This is the figure of the circuit.


In this circuit, the 1K load resistor is tied to the speaker so that as the output moves negative, the voltage on the 1K resistor is reduced, which aids in turning off the top NPN transistor. When the output moves positive, the charge on the 470uF capacitor aids in turning on the top NPN transistor. The original circuit in the radio used a 300 ohm resistor where the 2 diodes are shown but I changed the resistor to 2 diodes so the amp would operate on lower voltages with less distortion. The transistors shown 2n3053 and 2n2905 are just parts I used for the other circuit above and could be smaller types. Most any small transistors can be used, but they should be capable of 100mA or more current. A 2N3904 or 2N3906 are probably a little small, but would work at low volume.

The 2 diodes generate a fairly constant bias voltage as the battery drains and reduces crossover distortion. But you should take care to insure the idle current is around 10 to 20 milliamps with no signal and the output transistors do not get hot under load. The circuit should work with a regular 8 ohm speaker, but the output power may be somewhat less. To optimize the operation, select a resistor where the 100K is shown to set the output voltage at 1/2 the supply voltage (4.5 volts). This resistor might be anything from 50K to 700K depending on the gain of the transistor used where the 3904 is shown.

This Fm rf power amplifier has 2 transistors from Philips : BLV 10 and BLW 87. The 2 rf transistors work in class C and this fm amplifier has a total gain of 21dB ( 100 X ) and efficiency 55 – 65%.
One low pass filter with 9 components ensures 60dB rejection on the second harmonic. There is no need for tune-up to cover the whole 88 – 108 MHz FM frequencies.


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