24 Questions
What is the total phase shift provided by the C-R ladder network?
180°
What is the minimum gain required for the amplifier to sustain oscillation in a Wien bridge oscillator?
29
What is the application of Wien bridge oscillators?
Audio applications
What is the frequency at which the phase shift will be zero in a Wien bridge network?
Resonant frequency
What is the purpose of the op-amp in a C-R ladder network oscillator?
To provide a phase shift of 180°
What is the application of C-R ladder network oscillators?
Musical instruments
What is the condition for oscillation in a Wien bridge oscillator?
The amplifier gain is greater than 29
What is the use of the C-R ladder network in an oscillator circuit?
To provide a phase shift that varies with frequency
What is the output voltage of the summing amplifier if V1 = 6V, V2 = -3V, and V3 = -0.75V, given Rf = 10KΩ, R1 = 10KΩ, R2 = 2.2KΩ, and R3 = 3.3KΩ?
-1.5V
What is the purpose of positive feedback in amplifier circuits?
To reinforce the input signal and increase the overall gain
What is the condition for an amplifier to oscillate with positive feedback?
When the loop gain is equal to unity
What is the output waveform of the circuit shown in the figure when a sine wave of 1Vpeak at 1000Hz is applied?
A sine wave
What is the effect of positive feedback on the overall gain of an amplifier?
It increases the overall gain
What is the purpose of using an Op-amp in the circuit shown in the figure?
To amplify the input signal
What is the output waveform of the differentiator circuit when a triangular wave is applied at the input?
A square wave
What is the output waveform of the differentiator circuit when a square wave is applied at the input?
A spike waveform
What is the primary purpose of crystal controlled oscillators?
To maintain an exact frequency of oscillation
What is the principle behind the operation of crystal oscillators?
Piezoelectric effect
What determines the frequency of oscillation in a crystal oscillator?
The cut and physical size of the quartz crystal
What happens when the frequency of the applied voltage is equal to the natural frequency of the crystal?
Resonance takes place and crystal vibrations reach a maximum value
What is the series resonant frequency (fs) in a crystal oscillator?
The frequency at which the reactance of the capacitance C is equal to the reactance of the inductance L
What is the parallel resonant frequency (fp) in a crystal oscillator?
The frequency at which the reactance of R-L-C branch is equal to the reactance of capacitor Cm
What is the range of C required to generate frequencies from 1KHz to 100 kHz?
Not specified in the content
What is the electrical equivalent circuit of a crystal?
A series R-L-C circuit in parallel with a mounting capacitance Cm
Study Notes
Crystal Controlled Oscillators
- Used to maintain an exact frequency of oscillation accurately
- Quartz crystal is used as the frequency determining element
- Operates on the principle of piezoelectric effect
- The frequency of oscillation is determined by the crystal's 'cut' and physical size
- Resonance occurs when the frequency of the applied voltage is equal to the natural frequency of the crystal
Equivalent Circuit of a Crystal
- Consists of a series R-L-C circuit in parallel with a mounting capacitance Cm
- Two resonant frequencies: series resonant frequency (fs) and parallel resonant frequency (fp)
Problems
- The series resonant frequency (fs) occurs when the reactance of the inductance (L) is equal to the reactance of the capacitance C
- The parallel resonant frequency (fp) occurs when the reactance of R-L-C branch is equal to the reactance of capacitor Cm
Oscillators
- Circuits that generate an output signal without the need for an input signal
- Positive feedback is used to create oscillators
- When the loop gain approaches unity (or larger), it results in an unstable amplifier with infinite gain
- Oscillators can be used in applications such as musical instruments, GPS units, and voice synthesis
Wien Bridge Oscillator
- A phase shift oscillator based on a Wien bridge network
- Provides 0° phase shift at a particular frequency (called resonant frequency)
- The frequency at which the phase shift will be zero is: f = 1 / (2π√(R1R2C1C2))
- The minimum amplifier gain required to sustain oscillation is: Av > 1 / (2√(R1/R2))
RC Ladder Network Oscillator
- The frequency of oscillation is determined by the values of R and C
- The total phase shift provided by the C-R ladder network is 180° at the frequency of oscillation
This quiz is about crystal controlled oscillators, which are used to maintain an exact frequency of oscillation. It focuses on the frequency range of C in oscillators that generate frequencies from 1KHz to 100 kHz.
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