Doorbell for Deaf People.
When a deaf person is alone in a house, it would be very difficult to realize that someone is knocking on the door without any visual warning signal.
Crystal Oscillators – Piezoelectric Oscillator. Equivalente circuit
The Crystal Oscillators (Piezoelectric Oscillator) A quartz crystal has a property called: piezoelectric effect. This effect causes, by applying a mechanical pressure on the surface of the crystal, that a voltage is developed on the opposite sides. In a similar way, a voltage applied on the faces of the crystal produces a mechanical distortion on their surface. An AC voltage causes […]
LC Oscillator – Inductance – Capacitance Oscillator
LC oscillator: Inductance – Capacitance Oscillator A simple oscillator can be built with an amplifier stage and an inductive-capacitive network (LC) to provide an offset of -180° The oscillation frequency can be freely adjusted or tuned on a range of frequencies from 100kHz to a few hundred MHz by changing only the value of C or L. These LC […]
Phase Shift Oscillator
The Phase Shift Oscillator The phase shift oscillator, whose basic structure is described in the picture 1.a has a a negative gain amplifier (-K) and a feedback network consisting of a third order RC section in cascade. The oscillation condition requires that the feedback network produce a phase shift of 180° to be consistent with the negative gain amplifier which […]
Wien-bridge Oscillator with Op Amp
Wien-bridge Oscillator using Op-Amp The Wien-bridge oscillator, as shown on the basic outline of the diagram below, consists of an Operational Amplifier (OA) in a non-inverting configuration with gain 1+R2/R1 and a RC feedback network with the following transfer function: Where: Combining the first and the second equation we get: The loop gain (BA) is: The Barkhausen criterion […]
Sinusoidal oscillators – Basic principles
Sinusoidal Oscillators Sinusoidal oscillators play an important role in electronic systems that use harmonic signals. Despite that, in many instances are known as linear oscillators, it is necessary to use some non-linear feature to generate a sine wave output. In fact, the sinusoidal oscillators are essentially non-linear which complicates the technical design and analysis of such circuits. The […]