Portable Microphone Preamplifier by BC550C

Saturday, February 16th, 2008


High headroom input circuitry
9V Battery powered
This circuit is mainly intended to provide common home stereo amplifiers with a microphone input. The battery supply is a good compromise: in this manner the input circuit is free from mains low frequency hum pick-up and connection to the amplifier is more simple, due to the absence of mains [...]

Class A Buffer preamplifier by BC550

Tuesday, February 12th, 2008


A unit which is often very useful, if we need to isolate, in sound circuits, two stage between them. Then we can use this circuit which has an amplified unit, which gain X1, we do not use total negative feedback, only local, with the result that distortion remains at a very low level. Matching must [...]

High Temperature ALARM by BC550

Wednesday, October 10th, 2007


The circuit is small regulatorof temperature, us warns for the increase of temperature. The control of temperature becomes from the thermistor TH1, that is negative factor. His resistance is altered between in the 10K in temperature 25° C and roughly in the 1K in their 94° C. The trimmer TR1 regulates the precise temperature in [...]