Motor speed regulator with triac
This triac-based motor speed regulator is designed for controlling the speed of small household motors like drill machines. The speed of the motor can be controlled by changing the setting of P1. The setting of P1 determines the phase of the trigger pulse that fires the triac.
The circuit incorporates a self-stabilizing technique that maintains the speed of the motor even when it is loaded. For example, when the motor of the drill machine is slowed down by the resistance of the drilled object, the counter-EMF of the motor also decreases. This results to a
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Low noise preamplifier
A preamplifier circuit with a very low noise characteristic can be built by simply combining a FET transistor with a bipolar one.
The input impedance of the preamp circuit is almost the same as the gate impedance of the FET transistor (around 1MΩ) The output impedance at the other end is about 1KΩ.
The frequency of this preamplifier is linear (-3dB) between 10 Hz and 450 kHz and -1dB between 20 Hz and 200 kHz. The amplifying factor is aroung 100.
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TEA1039 datasheet
The TEA1039 is a bipolar integrated circuit intended for the control of a switched-mode power supply. Together with an external error amplifier and a voltage regulator (e.g. a regulator diode) it forms a complete control system. The circuit is capable of directly driving the SMPS power transistor in small SMPS systems.
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