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In a circuit with a capacitor filter, what is the primary function of the output capacitor?
In a circuit with a capacitor filter, what is the primary function of the output capacitor?
Acts as a line filter to improve transient response
What is the purpose of the input capacitor in a circuit with a voltage regulator?
What is the purpose of the input capacitor in a circuit with a voltage regulator?
To prevent unwanted oscillations
What IC series is commonly used for fixed negative voltage regulation?
What IC series is commonly used for fixed negative voltage regulation?
The 7900 series
What is the output voltage of a 7912 IC regulator?
What is the output voltage of a 7912 IC regulator?
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What are the three terminals of the LM317 adjustable voltage regulator?
What are the three terminals of the LM317 adjustable voltage regulator?
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How is the output voltage of the LM317 adjustable voltage regulator changed?
How is the output voltage of the LM317 adjustable voltage regulator changed?
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What is the adjustable output voltage range of the LM317 regulator?
What is the adjustable output voltage range of the LM317 regulator?
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Besides voltage regulation, what is another specification that is important for the LM317?
Besides voltage regulation, what is another specification that is important for the LM317?
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A power supply has a change in output voltage of 0.5V when the load current changes by 1A. What is the output impedance?
A power supply has a change in output voltage of 0.5V when the load current changes by 1A. What is the output impedance?
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A power supply has an output impedance of 0.5 ohms. If the load current decreases, and the output voltage when loaded is 10.5V, what is the no-load voltage?
A power supply has an output impedance of 0.5 ohms. If the load current decreases, and the output voltage when loaded is 10.5V, what is the no-load voltage?
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A power supply with an output impedance of 0.01 Ω has a load current that varies between 0.5A and 1A. What is the peak to peak change in output voltage?
A power supply with an output impedance of 0.01 Ω has a load current that varies between 0.5A and 1A. What is the peak to peak change in output voltage?
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For a power supply, is it better to have a higher or lower output impedance?
For a power supply, is it better to have a higher or lower output impedance?
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A voltage regulator experiences a 10 μV change in its output voltage when its input voltage changes by 5V. What is the line regulation?
A voltage regulator experiences a 10 μV change in its output voltage when its input voltage changes by 5V. What is the line regulation?
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A power supply's output impedance is calculated by dividing the change in what value, by the change in load current?
A power supply's output impedance is calculated by dividing the change in what value, by the change in load current?
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When specifying a power supply, what is an important consideration related to its output characteristics?
When specifying a power supply, what is an important consideration related to its output characteristics?
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In electronic systems with rapidly changing loads, how does the output impedance of a power supply typically behave with respect to the frequency of the load change?
In electronic systems with rapidly changing loads, how does the output impedance of a power supply typically behave with respect to the frequency of the load change?
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What does a line regulation of 2 μV/V for a voltage regulator signify?
What does a line regulation of 2 μV/V for a voltage regulator signify?
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What is the primary function of a regulated DC power supply?
What is the primary function of a regulated DC power supply?
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List the basic components of a regulated power supply.
List the basic components of a regulated power supply.
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What are the three main circuits comprising the regulated power supply described?
What are the three main circuits comprising the regulated power supply described?
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What is the purpose of the bridge rectifier in a regulated power supply?
What is the purpose of the bridge rectifier in a regulated power supply?
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What role does the capacitor filter play in a regulated power supply?
What role does the capacitor filter play in a regulated power supply?
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What are the two main functions of the zener voltage regulator?
What are the two main functions of the zener voltage regulator?
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What is a primary disadvantage of using a simple zener regulator?
What is a primary disadvantage of using a simple zener regulator?
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In a zener diode voltage regulator, what limits the minimum value of the series resistor ($R_S$)?
In a zener diode voltage regulator, what limits the minimum value of the series resistor ($R_S$)?
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In a series feedback voltage regulator, what does the feedback fraction (m) represent?
In a series feedback voltage regulator, what does the feedback fraction (m) represent?
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In the context of Example 17.11, what is the minimum current through the zener diode ($I_Z(min)$) when calculating the maximum value of $R_S$?
In the context of Example 17.11, what is the minimum current through the zener diode ($I_Z(min)$) when calculating the maximum value of $R_S$?
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How is the closed-loop voltage gain (ACL) related to the feedback fraction (m) in a series voltage regulator?
How is the closed-loop voltage gain (ACL) related to the feedback fraction (m) in a series voltage regulator?
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In a transistor series voltage regulator, what component provides the reference voltage?
In a transistor series voltage regulator, what component provides the reference voltage?
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What two voltage components that determine the output voltage of a series voltage regulator?
What two voltage components that determine the output voltage of a series voltage regulator?
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What happens to the output voltage of a transistor series voltage regulator if the base-emitter voltage ($V_{BE}$) increases?
What happens to the output voltage of a transistor series voltage regulator if the base-emitter voltage ($V_{BE}$) increases?
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What is the primary drawback of a series voltage regulator related to the pass transistor?
What is the primary drawback of a series voltage regulator related to the pass transistor?
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What is the relationship between $V_{out}$, $V_Z$ and $V_{BE}$ in a transistor series voltage regulator?
What is the relationship between $V_{out}$, $V_Z$ and $V_{BE}$ in a transistor series voltage regulator?
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What is the purpose of adding a current limiting circuit to a series voltage regulator?
What is the purpose of adding a current limiting circuit to a series voltage regulator?
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In the current limiting circuit described, what role (on or off) does transistor Q3 play during normal load current conditions?
In the current limiting circuit described, what role (on or off) does transistor Q3 play during normal load current conditions?
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In a series voltage regulator, why is the transistor labeled as a 'series' transistor?
In a series voltage regulator, why is the transistor labeled as a 'series' transistor?
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If the output voltage in a transistor series regulator decreases, how does the circuit respond to restore the output voltage?
If the output voltage in a transistor series regulator decreases, how does the circuit respond to restore the output voltage?
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What happens to transistor Q3 when excessive load current flows in a voltage regulator with current limiting?
What happens to transistor Q3 when excessive load current flows in a voltage regulator with current limiting?
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How does turning on Q3 in a current limiting circuit prevent the increase in load current?
How does turning on Q3 in a current limiting circuit prevent the increase in load current?
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What is the maximum base current, $I_B (max)$, given that $\beta = 50$ and $I_C(max) = 1A?
What is the maximum base current, $I_B (max)$, given that $\beta = 50$ and $I_C(max) = 1A?
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What is the minimum zener current, $I_Z (min)$, used in the calculation of $I_{RS}$?
What is the minimum zener current, $I_Z (min)$, used in the calculation of $I_{RS}$?
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What is the total current through $R_S$, denoted as $I_{RS}$, and how is it calculated?
What is the total current through $R_S$, denoted as $I_{RS}$, and how is it calculated?
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When calculating the value of $R_S$, why is the minimum input voltage ($V_{in}(min)$) used?
When calculating the value of $R_S$, why is the minimum input voltage ($V_{in}(min)$) used?
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Calculate the value of $R_S$ when $V_{in}(min) = 12V$, zener voltage $V_Z = 8.5V$, and $I_{RS} = 21mA$.
Calculate the value of $R_S$ when $V_{in}(min) = 12V$, zener voltage $V_Z = 8.5V$, and $I_{RS} = 21mA$.
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Under what conditions does maximum power dissipation in $R_S$ occur?
Under what conditions does maximum power dissipation in $R_S$ occur?
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What is the maximum voltage across $R_S$, denoted as $V_{RS}(max)$, when $V_{in}(max) = 18V$ and $V_Z = 8.5V$?
What is the maximum voltage across $R_S$, denoted as $V_{RS}(max)$, when $V_{in}(max) = 18V$ and $V_Z = 8.5V$?
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When does the maximum power dissipation in the zener diode occur?
When does the maximum power dissipation in the zener diode occur?
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Study Notes
Regulated D.C. Power Supply
- Electronic circuits using tubes or transistors require a direct current (DC) power source.
- Batteries are costly and require frequent replacement.
- DC power for electronic circuits is obtained from AC mains using rectifier-filter systems (DC power supplies).
- Ordinary DC power supplies contain a rectifier and filter circuit.
- Rectifier output is pulsating DC, containing AC components.
- Filter circuits remove the AC components, providing steady DC voltage.
Limitations of Ordinary DC Power Supplies
- Output voltage directly varies with input AC voltage.
- Output voltage decreases with increasing load current.
- This variation negatively impacts the operation of electronic circuits like oscillators and transmitters.
Important Terms
- Voltage Regulation: The variation of output voltage with changes in load current. Expressed as a percentage: (Vno-load - Vfull-load) / Vfull-load × 100.
- Minimum load resistance: A minimum load resistance is necessary for a power supply to deliver the rated output voltage and current.
Operational Concerns
- Proper operation requires a specific zener current range (Iz).
- Series resistance (Rs) limits the maximum input current for the circuit's safe operation.
- There is a minimum load resistance requirement to activate the zener diode's regulation.
- If maximum power dissipation of a zener is PZ(max) and the zener voltage is Vz, then Iz(max) = PZ(max) / Vz.
- For a reliable power supply, the voltage variation between no-load and full-load should be minimized.
Types of Voltage Regulators
- Series Voltage Regulator: Placed in series with the load.
- Shunt Voltage Regulator: Placed in parallel with the load.
Zener Diode Voltage Regulator
- Zener diodes maintain a constant voltage across the load, despite changes in current.
- Suitable for low-voltage applications.
- Series limiting resistance (Rs) is used to control the current through the diode.
Transistor Series Voltage Regulator
- Uses transistors and a zener diode for stability.
- Reference voltage is established by the zener diode.
- A larger increase in load current will cause lesser current through zener diode.
- Output is independent of changes in input voltage or load current variation.
Series Feedback Voltage Regulator
- Uses feedback to regulate output voltage, more stable than a simple zener-based regulator.
- Pass transistor (Q₂) conducts most of the load current.
- Sample/adjust circuit using resistors (R₁ and R₂) provides a feedback voltage to control Q₁.
Short-Circuit Protection
- Added to series regulators to protect them from excessive load current (e.g., shorting).
- Protects the pass transistor from damage.
- A current-limiting circuit (using a transistor Q3 and resistor R4) is added.
- The decrease in base voltage of Q₂ reduces pass transistor conduction and prevents further increase in load current.
Glow-Tube Voltage Regulator
- Maintains constant voltage despite load changes using a glow tube.
- Suitable for moderate input voltages.
- Typically used in places requiring moderate-output voltages.
- Load variation does not affect output voltage.
Series Triode Voltage Regulator
- Uses triodes instead of transistors.
- Output voltage remains constant independent of load current.
- Maintains regulated voltage despite input voltage variations.
- Potentially wider input voltage range compared to other regulators.
Series Double Triode Voltage Regulator
- Uses two triodes for a more stable output than single triode regulators.
- Provides improved regulation compared to earlier versions, due to negative feedback.
IC Voltage Regulators
- Integrated circuits (ICs) with built-in functionalities for voltage regulation.
- Fixed positive regulators (e.g., 7805): Provides a fixed positive output voltage.
- Fixed negative regulators (e.g., 7905): Provides a fixed negative output voltage.
- Adjustable regulators (e.g., LM317): Allows adjustable output voltage.
- Dual-tracking regulators: Provide both positive and negative output voltages using one device.
Additional notes:
- Different regulator types have varying limitations and applications.
- Selection of appropriate regulator depends on specific needs.
- Key components required for creating a regulated power system are:
- Unregulated DC input
- Regulator circuit (various components)
- Load
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Description
This quiz covers the fundamentals of regulated DC power supplies used in electronic circuits. It discusses the importance of rectifier-filter systems and the limitations of ordinary DC power supplies, focusing on voltage regulation and its impact on circuit performance. Test your knowledge on key concepts and terminology related to DC power sources.
