Capacitance multiplier

Abstract

The invention provides a capacitance multiplier which employs an active device. Since the area of the active device is intrinsically smaller than that of a passive device, and the capacitance multiplier only comprises four transistors and a capacitor and is simple in structure, the capacitance multiplier is small in area, and cost of an integral chip can be reduced. Further, noise generated by the whole capacitance multiplier is low as devices are less, so that improvement of the noise performance of a whole circuit is benefited.

Description

technical field [0001] The invention relates to the technical field of integrated circuits, in particular to a capacitance multiplier. Background technique [0002] A capacitor multiplier can be applied to a loop filter in a Phase Locked Loop (PLL, Phase Locked Loop). Traditional loop filters use passive capacitors and resistors to design circuits. Under the requirements of PLL performance, the value of capacitors will be very large. If the loop filter is designed using the on-chip method, the process determines that the capacitor occupies a large area, exceeding 50% of the entire PLL area. With the shrinking of process feature size, the area of ​​transistors is also shrinking, but the impact on the area of ​​passive devices is very small, thus restricting the reduction of chip cost. [0003] To sum up, the current capacitor multiplier has a relatively large area and occupies a large proportion of the entire chip area, which will increase the cost of the entire chip. At t...

AI Technical Summary

Problems solved by technology

With the continuous reduction of process feature size, the area of ​​transistors is also continuously reduced, but the impact on the area of ​​passive devices is very small, which restricts the reduction of chip cost

[0003] To sum up, the current capacitor multiplier has a large area and occupies a large proportion of the entire chip area, which will increase the cost of the entire chip

At the same time, the circuit structure of the current capacitor multiplier using passive components is complex, therefore, it will affect the noise performance of the entire circuit

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