100W subwoofer amplifier

General Description:

     This is the circuit diagram of a fully transistorized sub woofer amplifier that can produce an output of 100W.There are seven transistors including four in the output stage. The transistors Q1 and Q2 form the preamplifier stage. Transistors Q4 to Q7 form the output stage. Since no ICs are used the circuit is very robust and can be easily assembled on a general purpose PCB.

Circuits features:

• The circuit can be powered from a +35V/-35V, 5A dual power supply.
• Use a 100W, 12 inch sub woofer at the output.
• All electrolytic capacitors must be rated 100V.
• The transistor Q4 to Q7 must be fitted with heat sinks.

Circuit Diagram:

100W subwoofer amplifier circuit

Dynamic microphone Amplifier for earphones

I decided to make this circuit so that I could listen to faint noises. It is a simple two-stage transistor amplifier design. The circuit was designed to use the input from a dynamic microphone but I am sure that with some modifications it would be possible to use an electret microphone. The 2N3053 transistors used in the design don’t have a particularly high gain so other types could probably be used as long as they are NPN.
source: eleccircuit.com

Computer Microphone

      This circuit was submitted by Lazar Pancic from Yugoslavia. The sound card for a PC generally has a microphone input, speaker output and sometimes line inputs and outputs. The mic input is designed for dynamic microphones only in impedance range of 200 to 600 ohms. Lazar has adapted the sound card to use a common electret microphone using this circuit. He has made a composite amplifier using two transistors. The BC413B operates in common emitter to give a slight boost to the mic signal. This is followed by an emitter follower stage using the BC547C. This is necessary as the mic and circuit and battery will be some distance from the sound card, the low output impedance of the circuit and screened cable ensuring a clean signal with minimum noise pickup. original article soruse: eleccircuit.com

How to make 3V from one battery AA 1.5V

How to make 3V from one battery AA 1.5V

Telephone AmplifierLF351 and TBA820M

Amplifier description:

This circuit TDA820M Mini Amplifier 2W+2W. Supply Volt 12V, Easy to build and Low cost. If you want mini amplifier circuit , as a result do not be defeated certainly. The sound will a little 2W+2W just but enough with 6 sizes are inch 8ohm loudspeakers. as a result still have a voice good loud the moderately. Request friends have fun the circuit amplifies this miniature please yes.

Circuit diagram:

PCB layout:

In Mono style a few parts and very cheap!
TBA820 mini AUDIO AMPLIFIER 1.2W
Here is Circuit Mini power amplifier low watt (1.2W Only). IN circuit have IC TBA820,it old IC Audio amp.

 

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Low Power Wireless Audio Power Amplifier

     Using this low-cost project one can reproduce audio from TV without disturbing others. It does not use any wire connection between TV and Loud Speaker. In place of a pair of wires, it uses invisible infra-red light to transmit audio signals from TV to Loud speakers, Without using any lens a range of up to 6 meters is possible. Range can be extended by using lenses and reflectors with IR sensors comprising transmitters and receivers.

     IR transmitter uses two-stage transistor amplifier to drive two series-connected IR LEDs. An audio output transformer (T1) is used (in reverse) to couple audio output from TV to the IR transmitter. Transistors Q1 and Q2 amplify the audio signals received from TV through the audio transformer. Low impedance output windings (lower gauge or thicker wires) are used for connection to TV side while high-impedance windings are connected to IR transmitter. This IR transmitter can be powered from a 9V mains adapter or a 9V battery. Red LED (D1) in transmitter circuit functions as a Zener diode (0.65V) as well as supply-on indicator.

Transmitter diagram:

Wireless Audio Power Amplifier Transmitter Circuit Diagram

Receiver's operation:

      IR receiver uses popular op-amp IC µA741 and audio-frequency amplifier IC LM386 along with phototransistor L14F1 (Q3) and some discrete components. The sound generated by TV set is transmitted through IR LEDs, received by phototransistor Q3 and fed to pin 2 of IC µA741 (IC1). Its gain can be varied using potmeter P2. The output of IC µA741 is fed to IC LM386 (IC2) via capacitor (C7) and potmeter P3. The sound produced is heard through the receiver’s loudspeaker. Potmeter P3 is used to control the volume of loudspeaker SPKR (8-ohm, 1W).

Receiver diagram:

Wireless Audio Power Amplifier Transmitter Circuit Diagram

Parts:

P1 = 10K

P3 = 10K

P2 = 1M

R1 = 4.7K

R2 = 22K

R3 = 100R

R4 = 10R-1W

R5 = 10K

R6 = 10K

R7 = 15K

R8 = 15K

R9 = 100K

R10 = 680R-1W

R11 = 1K

R12 = 10R-1W

C1 = 220uF-25V

C2 = 220uF-25V

C3 = 10uF-25V

C4 = 220uF-25V

C5 = 220uF-25V

C6 = 100nF-63V

C7 = 100nF-63V

C8 = 100nF-63V

C9 = 100nF-63V

D1 = Red LED

D2 = IR LEDs

D3 = IR LEDs

Q1 = BC547

Q2 = BD140

Q3 = L14F1

IC1 = uA741 Opamp

IC2 = LM386

J1 = Audio input Jack

T1 = Audio Transformer

SPKR = 1W-8ohm

LM4910 Stereo Headphone Amplifier

Circuit description:    

      LM4910 belonging to the Boomer series of National Semiconductors is an integrated stereo amplifier primarily intended for stereo headphone applications. The IC can be operated from 3.3V ans its can deliver 0.35mW output power into a 32 ohm load. The LM4910 has very low distortion ( less than 1%) and the shutdown current is less than 1uA. This low shut down current makes it suitable for battery operated applications. The IC is so designed that there is no need of the output coupling capacitors, half supply by-pass capacitors and bootstrap capacitors. Other features of the IC are turn ON/OFF click elimination, externally programmable gain etc.

Circuit diagram:  

     Circuit diagram of the LM4910 stereo headphone amplifier is shown above.C1 and C2 are the input DC decoupling capacitors for the left and right input channels. R1 and R2 are the respective input resistors. R3 is the feed back resistor for left channel while R4 is the feed back resistor for the right channel. C3 is the power supply filter capacitor. The feedback resistors also sets the closed loop gain in conjunction with the corresponding input resistors.

The IC is available only in SMD packages and care must be taken while soldering. 

The circuit can be powered from anything between 2.2V to 5V DC. 

The load can be a 32 ohm headphone. 

Absolute maximum supply voltage is 6V and anything above it will destroy the IC. 

A logic low voltage at the shutdown pins shut downs the IC and a logic high voltage at the same pin activates the IC. Original aritcle sourse circuitsproject.com