Easy Test power battery by BC547

Saturday, October 11th, 2008

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A friends at use the battery often meet a problem electric its energy is finished in important always may many good if there is the circuit warns before or there is the way checks at the beginning. By this circuit use the transistor just one and don’t have to have power supply [...]

ECM Mic Preamplifier by BC549

Saturday, April 19th, 2008

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A microphone amplifier that may be used with either Electret Condenser Microphone (ECM) inserts or dynamic inserts, made with discrete components.
Both transistors should be low noise types. In the original circuit, I used BC650C which is an ultra low noise device. These transistors are now hard to find but BC549C or BC109C are a good [...]

Low Voltage Preamplifier by BC549

Tuesday, February 12th, 2008

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A low voltage preamplifier optimised for 3 Volt operation.
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.
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