2B-MUTIPURPOSE MINI MIKE AMPLIFIER
This low cost project can be used in your houses , shops and schools. You can attach this project to your telephone , use as classroom address system or attach to any low sound device to amplify its sound. Also you can double the sound of your pocket transistor with the help of this project.
TECHNICAL DESCRIPTION AND WORKING
This project has been developed and tested O.K. in our TV Engineers Technical Lab. The components and PCB used in the projects published in our books are available for sale at resonable price.
This project is an old project, but it is an unique one in the age of electronics. With the help of this project,you can hear a low sound. It has the abaility to catch a very very low sound. Therfore, you can use it for recording purpose also. This project is based on IC 741. IC 741 is an operational amplifier whose gain is very high. At Pin no. 2 of the IC 741, information is applied via condensor mike. The condensor mike is supplied positive voltage through a resistance 4k7. The gain of the amplifier depends upon the feedback, applied through a 1M resistance. This feedback can be adjusted by the preset. The output of IC available at its pin no. 6 is amplified by an amplifier comprising of two transistors. This project operates on + 9 Volt DC supply.
PRECAUTIONS WHILE ASSEMBLING THE PROJECT:-
*First of all check all the components as per circuit.
*While mounting transistor, you should connect collect
or , base & emitter properly.
*Please use resistance of the exact value as given in the circuit.
*Use IC base for mounting of the ICs otherwise IC may damage due to current leakage of solderinf iron.
*Check polarity of electrolytic capacitor while mounting on PCB otherwise reverse connection may damage it.
*Check polarity of condenser mike while mounting.
IC 741 = 1
BC 148 = 1
BC 158 = 1
470MFD/25V = 1
.04 = 1
4.7K = 1
3.3K = 1
10K = 2
1M VOL. CONTROL = 1
CONDENSOR MIKE = 1
SPEAKER = 1