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Electronic Amplifier Circuits-Power amplifier, audio amplifier designs and circuits

August 21st, 2009

Simple Amplifier circuit for Headphones

About The Circuit

Though the headphones that are present in the market today are good enough, the music player may not be able to provide enough power to drive the headphone. The only way to make them produce a clear and gud sound is to amplify them. For this, a very simple circuit is enough consisting of three amplifiers. The circuit only needs a 3 Volts battery and needs to be made on a good quality Printed Circuit Board.
The transistors used for this circuit are BC 239 BC 337 and BC 327. Out of these Q1 (BC 239) acts as the pre-amplifier, while transistors Q2 (BC 337) and Q3 (BC 327) act as the driver circuit for the speaker. The performance of the circuit is increased by feeding back the emitter voltage of Q1 the base of Q1 itself through the resistance R3. You must also note down that the capacitors have a rating of 10 Volts. After the circuit is made all you have to do is ON/OFF the switch S1.

 

Circuit Schematic

 

amplifier-circuit-for-headphone.JPG

August 21st, 2009

Guitar Pre-amplifier Circuit

About The Circuit

Here is a simple guitar pre-amplifier circuit. The circuit is designed for high oimpedance type electric guitar pickups. An op-amp IC uA 741 is all that is required. uA 741 IC is IC1 which acts as the non-inverting amplifier. The volume can be controlled with the help of POT R1 and the tone can be controlled with the help of POT R6. The tone effects can be adjusted to “SOFT” and “BRILLIANT” modes with the help of switch S1.

An input voltage of 12 Volt DC power supply or battery is more than enough, though a maximum of 24 Volts can be used.

Circuit Schematic

 

guitar-preamplifier-ua-7141.JPG

August 21st, 2009

Simple Audio Monitoring Circuit

About The Circuit

Here is the circuit diagram of an audio monitoring system which can be easily setup on a PCB. The main use of such a circuit is to transmit a sound from one location and to reproduce it on the other end with the help of a reciever. In this ciruit both the power supply as well as the signal that is transmitted share the same wire.

As seen in the figure, it must be noted that the terminal A is connected tp A’using the wire of required length. The same procedure must be followed for B to B’. A simple speaker of 8 Ohm and 2 Watts is required as K1. The gain of the transmitter circuit is controlled by the POT R2. while POT R14 is used to control the gain at the reciever end. A 12 Volt battery or 12 Volt DC power supply is enough as the input voltage.

The microphone M1 picks up the audio signals. The signals will then be amplified by the double stage amplifier build along with the transistors Q1 and Q2. The microphone has no special specifications. It can be a general purpose one. The by[pass of all the audio frequencies and noise from the line is done by the capacitor C4. C4 also ensures the pure DC for the circuit. The audio signal output of the amplifier is coupled to the line with the help of the capacitor C6. The audio signal from the line is extracted and is fed to the inverting input of TL 071, which is the IC1 in the circuit. This operation is done by the capacitor C7. The integrated power amplifier IC2 for which an LM 386 IC is used recieves the output of IC1. IC2 also provides all the necessary current gain to drive the speaker. The audio frequencies are isolated along with the noise from the power supply of both the IC’s with the help of capacitor C1.

Circuit Schematic

simple-audio-monitoring-circuit.jpg