Part E: Switched Capacitor Integrator (Optional/Advanced)
Key Concepts
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Resistor Emulation: Replacing a physical resistor with a switched capacitor and clock.
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Discrete-Time Operation: Integration occurs in steps, not continuously.
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Advantages in ICs: Area saving, precise ratio matching, programmability (via $f\_{CLK}$), CMOS compatibility.
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Critical Components: Op-Amp, $C\_S$, $C\_F$, Analog Switches, Two-Phase Clock.
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Non-overlapping Clock: Essential to prevent short circuits.
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Examples
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SC Filter: Beyond integrators, switched capacitor techniques are widely used to build highly accurate filters (low-pass, high-pass, band-pass) in ICs. Their cutoff frequencies can be tuned by changing the clock.
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Charge Pump: Another common SC circuit used to generate higher or lower DC voltages from a supply, particularly for flash memory or gate drivers.
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Sample-and-Hold Circuit: SC techniques are fundamental to the design of sample-and-hold circuits found at the input of many ADCs.
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Building Your Own Clock: You could use a 555 timer to generate a square wave, and then use a D-flip-flop and some gates to create two non-overlapping phases ($\phi\_1$ and $\phi\_2$) for the CD4066 switches.
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Flashcards
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Term: Switched Capacitor
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Definition: A circuit technique using capacitors and switches driven by a clock to emulate resistors and other analog components.
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Term: $R\_{eq}$ (Equivalent Resistance)
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Definition: The resistance mimicked by a switched capacitor, given by $1/(f\_{CLK} \times C\_S)$.
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Term: Non-Overlapping Clock
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Definition: A pair of clock phases ($\phi\_1, \phi\_2$) used in SC circuits where both are never high simultaneously, preventing shorts.
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Term: IC Area Saving (SC)
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Definition: An advantage of SC circuits where they use smaller capacitors to replace large resistors, reducing the physical size of ICs.
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Term: Programmability (SC)
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Definition: The ability to control circuit parameters (like cutoff frequency or integration rate) by digitally changing the clock frequency.
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Memory Aids
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"Capacitor is a Clock-Controlled Resistor": The core idea: a capacitor (C) acts like a resistor (R) when rapidly switched by a clock.
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"SC = Silicon Chip Saver": Switched Capacitors are great for Silicon Chips because they Save area and improve Control.
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"No Overlap, No Oops\!": The clock phases must be non-overlapping to prevent accidental short circuits ("oops\!").
Examples & Applications
SC Filter: Beyond integrators, switched capacitor techniques are widely used to build highly accurate filters (low-pass, high-pass, band-pass) in ICs. Their cutoff frequencies can be tuned by changing the clock.
Charge Pump: Another common SC circuit used to generate higher or lower DC voltages from a supply, particularly for flash memory or gate drivers.
Sample-and-Hold Circuit: SC techniques are fundamental to the design of sample-and-hold circuits found at the input of many ADCs.
Building Your Own Clock: You could use a 555 timer to generate a square wave, and then use a D-flip-flop and some gates to create two non-overlapping phases ($\phi\_1$ and $\phi\_2$) for the CD4066 switches.
Flashcards
Term: Switched Capacitor
Definition: A circuit technique using capacitors and switches driven by a clock to emulate resistors and other analog components.
Term: $R\_{eq}$ (Equivalent Resistance)
Definition: The resistance mimicked by a switched capacitor, given by $1/(f\_{CLK} \times C\_S)$.
Term: Non-Overlapping Clock
Definition: A pair of clock phases ($\phi\_1, \phi\_2$) used in SC circuits where both are never high simultaneously, preventing shorts.
Term: IC Area Saving (SC)
Definition: An advantage of SC circuits where they use smaller capacitors to replace large resistors, reducing the physical size of ICs.
Term: Programmability (SC)
Definition: The ability to control circuit parameters (like cutoff frequency or integration rate) by digitally changing the clock frequency.
Memory Aids
"Capacitor is a Clock-Controlled Resistor": The core idea: a capacitor (C) acts like a resistor (R) when rapidly switched by a clock.
"SC = Silicon Chip Saver": Switched Capacitors are great for Silicon Chips because they Save area and improve Control.
"No Overlap, No Oops\!": The clock phases must be non-overlapping to prevent accidental short circuits ("oops\!").
Memory Aids
Interactive tools to help you remember key concepts
Memory Tools
The core idea: a capacitor (C) acts like a resistor (R) when rapidly switched by a clock.
* "SC = Silicon Chip Saver"
Memory Tools
The clock phases must be non-overlapping to prevent accidental short circuits ("oops\!").
Flash Cards
Glossary
- CMOS (Complementary MetalOxideSemiconductor)
A dominant technology for fabricating integrated circuits, known for low power consumption.
- Nonoverlapping Clock
Essential to prevent short circuits.
- Building Your Own Clock
You could use a 555 timer to generate a square wave, and then use a D-flip-flop and some gates to create two non-overlapping phases ($\phi\_1$ and $\phi\_2$) for the CD4066 switches.
- Definition
The ability to control circuit parameters (like cutoff frequency or integration rate) by digitally changing the clock frequency.
- "No Overlap, No Oops\!"
The clock phases must be non-overlapping to prevent accidental short circuits ("oops\!").