OSCILLATORS Flashcards
Is a circuit that generates alternating current at a frequency determined by the values of its components.
-OSCILLATOR
Produces by using a positive feedback with a transistor, electron tube, magnetic amplifier or other amplifying device.
-OSCILLATOR
How these oscilliations are maintained?
BY DRAWING THE POWER FROM A BETTERY OR OTHER SOURCE POWER.
If BA ≤ 1, the output signal (oscillation) dies out.
-CONDITION 1
If BA < 1, the output signal builds up (osallation starts to grow).
-CONDITION 2
If BA = 1, the output signal level is fixed in
amplitude (sell- sustained oscilation).
-CONDITION 3
Is a parallel LC circuit that is capable of producing ac signal when excited by an external dc source.
-THE TANK CIRCUIT
The repetitive exchange of energy between the capacitor and the inductor is called the
-FLYWHEEL EFFECT
Common types of oscillators
- LC oscillators
a. Hartley Oscillator
b. Colpitts Oscillator
c. Clapp Oscilattor - Crystal Oscillators
a. Pierce Crystal Oscillator
b. Hartley Crystal Oscillator
c. Colpitts Crystal Oscillator - RC Oscillators
a. Phase-Shift Oscillator
b. Wen-Bridge Oscillator
Has two inductors a capacitor (L1, L2, and C) on its feedback network.
-THE HARTLEY OSCILLATOR
The three distinct types of Hartley oscillators are
- two coils L1 and 2 are uncoupled
- two independent coils with mutual coupling (L1, L2 with M)
- two parts of a single tapped coil
Widely used in signal generators operating in the frequency range about 100kHz to 500MHz.
-THE COLPITTS OSCILLATOR
It is composed of an inductor and capacitor in series such that the net reactance is inductive. This oscillator circuit provides a greater degree of stability compared to colpitts and hartley oscillator.
-THE CLAPP OSCILLATOR
Provides a very stable oscillation. The frequency drfit of crystal oscillator is only 0.0001% (1ppm) compared to 0.8% of LC osccilators/
-THE CRYSTAL OSCILLATOR
Types of crystal
- Rochelle salt crystal
- Tourmaline crystal
- Quartz crystal
Has the greatest piezoelectric activity therefore the weakest.
-ROCHELLE SALT CRYSTAL
Has the least piezoelectric activity therefore the strongest and the most expensive.
-TOURMALINE CRYSTAL
Has a characteristic that is midway between rochelle salt crystal and tourmaline crystal.
-QUARTZ CRYSTAL
Generation of a voltage between opposite faces of a crystal as a result of strain due to pressure or twisting and the reverse effect in which application of a voltage to opposite faces causes deformation.
-THE PIEZOELECTRIC EFFECT
It is inversely related to the thickness. Therefore, the thicker the crystal the lower is its what?
-FREQUENCY OF VIBRATION
Represent electrical equivalent of crystals mass and compliance.
-L AND Cs
Shunt capacitance represents the capacitance due to mechanical mounting of the crystal.
-Cm
electrical equivalent of the crystal structure internal friction
-R
A resonance, the reactance of the series branch is zero.
-SERIES RESONANT FREQUENCY
A resonance, the reactance of the crystal approaches infinity.
-PARALLEL RESONANT FREQUENCY
Basically a colpitts oscillator in which the inductor is replaced by a crystal.
-PIERCE CRYSTAL OSCILLATOR
Is a tuned circuit oscillator using a piezoelectric crystal as a resonant tank circuit.
-CRYSTAL OSCILLATOR
Is a vibration of a crystal from corner to corner.
-SHEAR
Is a vibration of a crystal from end to end.
-LONGITUDINAL
Is a vibration of a crystal in twisting movement.
-TORSIONAL
Is cutting perpendicular to the end to end.
-X CUT
Is cutting perpendicular to the face to face axis.
-Y CUT
It is an oscillator circuit that used three RC lead or lag sections in cascade, each with the same constant where at the frequency of oscillation. It is most often used to generate low-frequency sinusoidal signals for testing purposes.
-RC PHASE-SHIFT OSCILLATOR
Has one lead and one lag circuit in the feedback path and is using a non-inverting amplifier. It operates in the frequency range of 5Hz to 500kHz.
-WIEN BRIDGE OSCILLATOR
Is a relaxation oscillator ciruit that uses two active components that are coupled such that one of the components is conducting, while the other one is cut-off.
-MULTIVIBRATORS
Two classifications of multivibrations
- Self-excited
- Driven multivribator
Multivibrator which requires no external triggering
-SELF EXCITED
That requires an external triggering to excite the circuit and maintain the excitation.
-DRIVEN MULTIVIBRATOR
The two states
- Stable state
- Quasi-stable state
A state that will not change unless the circuit is disturbed.
-STABLE STATE
A state that remains unchanged for only a certain period of time.
-QUASI-STABLE STATE
This is commonly known as flip-flop. It has two stable states and no quasi stable state.
-BISTABLE BINARY MULTIVIBRATOR
This is also known as single-shot or one-shot multivibrator. It has one stable states and one quasi stable state.
-MONOSTABLE MULTIVIBRATOR
Also known as free running. It has no stable states but has two quasi stable state.
-ASTABLE VIBRATOR
