Electronic schematics, circuit designs
Dynamic microphone amplifier - low noise
This dynamic microphone amplifier circuit has a total gain of 200 times. If we use 200Ω microphones R4 must be 220Ω and C1 is 4.7uF. If you want the to get the lowest noise signal from this dynamic mic amplifier use metalic resistors for R3 .. R6 and for C1 use more MKM capacitor in parallel connection.
Some specification: with a 3mVpp input signal the output was 800mVpp. The maximum output voltage was 10Vpp when the input is 50mVpp. The frequencies domain is between 50Hz and 100KHz.
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Electret microphone amplifier circuit
This article describes an compact electret microphone amplifier but you can connect dynamic microphones with low resistance. Electret microphones can be inserted in the same box with the amplifier, it only need 5 to 10V or 9V battery with a current consumption of just 1.5mA.
Here you got the electret amplifier schematic:
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Wideband UHF Amplifier - antenna tv amplifier circuit
This UHF wideband amplifier ( Ultra High Frequency amplifier ) has a total gain of 10 to 15 dB in the 400 - 850 MHz domain frequency so it can be used where the tv signal is weak.
For this UHF antenna tv amplifier to work correctly you need to cut the components pins as short as possible. C1, C2, C6, C7 are SMD type ( surface mounted ). This antenna tv amplifier or uhf wideband amplifier need to be build inside of a metal box and then connected close to the tv antenna.
The power supply is a simple 12V stabilized source. The tv antenna amplifier can be connected directly to the power supply thru coaxial cable of the tv antenna but you need a 10 - 100uH coil on the alimentation line. The tv set will be connected to the uhf amplifier thru a small coupling capacitor.
Adjusting is easy, just bring the P1 to the middle and then adjust it untill you obtain the best tv image quality.
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