Circuit Project Electronic

Low Voltage Preamplifier using BC549
Sunday, October 26th, 2008

This is a special low voltage version of my audio preamp. T1’s emitter voltage is biased close to half supply voltage (1.5V) to allow for maximum output voltage swing. Both transistors are direct coupled and have closed loop feedback to aid temperature stability.
T2 realises the amplifiers full voltage gain, and for low noise operation, T2 [...]

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Headphone Amplifier with BC549
Sunday, October 26th, 2008

Both halves of the circuit are identical. Both inputs have a dc path to ground via the input 47k control which should be a dual log type potentiometer. The balance control is a single 47k linear potentiometer, which at center adjustment prevents even attenuation to both left and right input signals. If the balance control [...]

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500mW FM Transmitter by BC549
Friday, October 10th, 2008

The TX500 is a simple to build 500mW FM Transmitter. It consists of three blocks; modulator / oscillator, two stage 500mW VHF amplifier and LED based power meter. The TX500 allows to transmit audio signals to FM band at frequencies from 88 MHz to 108 MHz. Due to the very low power consumption of less [...]

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