Numerical Example - 6.4.1.5
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Understanding Phase Shift Oscillator Design
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Today, we are going to design a phase shift oscillator aiming for a frequency of 1 kHz. This involves calculating the required resistor value based on a given capacitor. Who can remind us what the formula for resistance is in this scenario?
Is it R = 1/(2ΟfCβ6)?
Exactly! Now, what values will we need to input into this formula to find R?
We need the frequency, which is 1 kHz, and the capacitor value, which is 10 nF.
Great! Plugging in these values gives us a roadmap for our calculations. Let's go ahead and compute R together.
So, we calculate R as 1 over 2Ο times 1000 times 10 nanofarads times the square root of 6, right?
Exactly! And once we find R, how do we verify if it's a standard resistor value?
We can check a standard resistor value table to find the closest one!
Perfect! Remember this approach for calculating component values in designing oscillators.
Calculating the Resistance Value
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Letβs work through the calculations step by step. What do we get if we first compute the denominator in the formula?
The denominator will be 2Ο times 1000 times 10 nanofarads times the square root of 6.
Correct! And how do we calculate $$\sqrt{6}$$?
It's approximately 2.449!
Exactly! Combining those values leads us to the value of R. Letβs do that math.
We get \(1 / (6.283 x 10^{-5})\) or approximately 6497 ohms.
Spot on! The next step is checking against standard resistor values. What do we find?
We would round that to 6.8 kΞ©.
Excellent! Understanding component values is crucial in design.
Op-Amp Configuration for Gain
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Now, letβs think about how to configure the op-amp. Why do we need to know the gain here?
To make sure it meets the requirements for sustained oscillation!
Exactly! Can someone remind us what the required gain is for this phase shift oscillator?
It needs to be at least 29.
Great job! How can we achieve this gain using feedback resistors?
If we use R_in at 1 kΞ©, then R_f should be at least 29 kΞ©.
Yes! Always ensure your op-amp gain meets or exceeds these values for optimal performance.
Introduction & Overview
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Quick Overview
Standard
In this section, we explore a specific numerical example for designing a phase shift oscillator aimed at achieving an oscillation frequency of 1 kHz. The example includes detailed calculations to determine the required resistor value, utilizing the relationships derived from theoretical principles of oscillators.
Detailed
Numerical Example of Designing a Phase Shift Oscillator
This section focuses on a practical application of designing a phase shift oscillator that operates at a frequency of 1 kHz using an op-amp. The oscillator is a specific type of RC oscillator where the necessary components include resistors (R) and capacitors (C) in the feedback path. The primary objective is to determine the appropriate value for R given a capacitor C.=10 nF.
Step-by-Step Calculations
To design the oscillator, we can use the formula derived in the theory section:
$$R = \frac{1}{2\pi f_0 C \sqrt{6}}$$
Substituting the known values:
- Oscillation Frequency: $$f_0 = 1 kHz$$
- Capacitor Value: $$C = 10 nF$$
This gives:
- $$R = \frac{1}{2\pi (1000 \text{ Hz})(10 \times 10^{-9} \text{ F}) \sqrt{6}}$$
Calculating this step-by-step:
1. Calculate the frequency product and capacitor product:
- $$2\pi(1000)(10 \times 10^{-9})\sqrt{6} \approx 6.283(10^{-6})(2.449) \approx 1.539 \times 10^{-5} \Omega$$
2. The reciprocal gives:
- $$R \approx 6497 \Omega$$
After considering standard values, it is determined that the closest standard resistor value of R is approximately 6.8 kΞ©. Finally, for the op-amp to achieve an inverting gain of at least 29, if the feedback resistors are chosen as R_in being 1 kΞ©, then:
- $$R_f \geq 29 \text{ kΞ©}$$
This numerical example concretely illustrates how theoretical principles can be applied in practice to design oscillators by calculating component values and ensuring the conditions to sustain oscillation are met.
Audio Book
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Phase Shift Oscillator Design
Chapter 1 of 3
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Chapter Content
Design a phase shift oscillator using an op-amp for f_0=1 kHz. Let C=10 nF.
Detailed Explanation
We start by designing a phase shift oscillator to generate a frequency of 1 kHz. The capacitor value (C) is given as 10 nF. The first step is to derive the resistor value (R) needed for the oscillator. Using the formula R = (1 / (2Οf_0C))β6, we substitute the known values into the equation. By solving this, we can calculate the required resistance to set the oscillator at the desired frequency.
Examples & Analogies
Think of designing this oscillator like tuning a musical instrument. Just as you'd adjust strings to reach a specific note (like 1 kHz), here, we're tweaking resistor values to hit our target frequency. The capacitor acts like a dynamic element, adjusting how quickly the circuit resonates.
Calculation of Resistor Value
Chapter 2 of 3
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Chapter Content
R = (
()C sqrt{6} = rac{Herr}{(1000 ext{ Hz} imes 10 imes 10^{-9} ext{ F}) imes rac{sqrt{6}}{6.283}}
Detailed Explanation
Upon inserting f_0 (1 kHz) and C (10 nF) into the equation, we calculate R. This results in a resistor value of approximately 6497
E. To make practical circuit design easier, we can use the nearest standard resistor value, which is 6.8 k
E. This might slightly affect performance, but it will work effectively for the intended frequency generation.
Examples & Analogies
Imagine you're at a bakery trying to bake bread but notice that you don't have the exact measure of flour needed. Instead, you take the closest measurement available to get a good result. Similarly, using a standard resistor value helps streamline the design while ensuring functionality.
Op-Amp Configuration and Gain Calculation
Chapter 3 of 3
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Chapter Content
The op-amp should be configured for an inverting gain of at least 29. If using feedback resistors R_f and R_in (for the op-amp input), A_v=R_f/R_in. So, R_f/R_in 30. If R_in=1 k
E, then R_f 30 k 0DE.
Detailed Explanation
After determining the resistor for the oscillator, we need to ensure the op-amp provides sufficient gain. The gain is expressed as A_v = R_f / R_in. For stability, we set A_v to at least 29. By assuming a feedback resistor value (R_in) of 1 k 0DE, we calculate the necessary feedback resistor (R_f) to maintain the gain over the desired level, resulting in R_f needing to be approximately 30 k 0DE.
Examples & Analogies
Think of this like a team effort in football (soccer). To win, each player needs to work together effectively. The resistors in the circuit play similar roles β some tackle the workload more than others while ensuring the overall strategy (gain) is achieved.
Key Concepts
-
Phase Shift Oscillator: A configuration using RC components for generating oscillations.
-
Feedback Resistor: A resistor used to control the gain of the op-amp.
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Standard Resistor Values: The commonly available resistor values from which one can choose.
Examples & Applications
Calculating the resistor value for achieving 1 kHz output frequency in phase shift oscillator.
Determining the feedback resistor configuration to achieve the desired gain in the op-amp.
Memory Aids
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Rhymes
To find R for the phase shift, use frequency with a lift; just plug C in the mix, and let the math do its tricks!
Stories
Imagine a chef (op-amp) needing just the right spice (gain) to create the perfect dish (oscillation). Too little spice results in bland food (no oscillation), while too much can spoil the meal!
Memory Tools
Remember 'RCF' for R (resistor), C (capacitor), F (frequency) to plan your phase shift oscillator.
Acronyms
Use 'PAF' to remember
for Phase Shift oscillator
for Amplifier gain
and F for Frequency.
Flash Cards
Glossary
- Phase Shift Oscillator
An oscillator that utilizes RC networks to create the necessary phase shift for sustained oscillation.
- Frequency
The number of oscillations per second, measured in Hertz (Hz).
- Capacitor
An electronic component that stores electrical energy in an electric field, characterized by its capacitance.
- Resistor
An electrical component that resists the flow of electric current, introducing a voltage drop.
Reference links
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