The analog and digital functionality are needed for any physical system design. How to achieve a modular, programmable design is important for the future requiring applications, thus more and more designs integrating subsystems and using mixed-signal architectures.

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How capacitor applied in programmable design
The analog and digital functionality are needed for any physical system design. How to achieve a
modular, programmable design is important for the future requiring applications, thus more and
more designs integrating subsystems and using mixed-signal architectures.
There are two great challenges for designers to face, and they are Dynamic changes and scalability.
How to overcome these two issues? Here we can use a modular, programmable design. It helps to
solve the problem associated with the porting of designs to different devices at a later stage in a
product’s lifecycle.
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Compared to fixed-function implementations, a programmable design allows a more flexible
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approach for these kinds of applications. However, achieving such flexibility in the analog domain
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still has been a challenge for developers. The use of switched capacitor circuits greatly helps
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resolve this issue
The basic building blocks of a programmable analog solution are Switched capacitor blocks. They
enable the integration of both analog and digital functions onto a single chip and define today’s
true system-on-chip (SoC) architectures. Conventional analog signal processing circuits use
continuous time circuits consisting of resistors, capacitors and operational amplifiers.
The ratio of resistances or magnitude of resistance or value of resistance and capacitor are used in
continuous time analog circuits to set transfer functions. It is absolutely true that the absolute
accuracy of resistance and capacitor using MOS technology is not good enough to perform analog
signal processing function.
While generally speaking, it is acceptable for using MOS technology to achieve the accuracy of a
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capacitor. What’s more, it is much easier for the fabrication of accurate small capacitors and it
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occupies less space using MOS technology as compared to that of resistance. Thus, we find
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switched capacitor circuits replacing conventional continuous time circuits in many buildings.
The use of a capacitor to emulateE
S resistance first is
connecting it in series with a battery, ammeter, and capacitor and periodically reversing the
capacitor. A similar method is used in switched capacitor circuits. Switched capacitor circuits use
capacitors to emulate resistance by controlling charge flow in and out of the capacitor using MOS
switches. Since charge flow defines the current, this in turn controls resistance.
It is worth noting that the equivalent resistance is inversely proportional to value of the capacitor
and switching frequency. This means that the resistance can be changed simply by changing either
the value of the capacitor or the switching frequency. In any system where digital resources are
available, it is relatively straightforward to change the switching frequency and thus the resistance.
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