Biquad unit for realizing band-pass filter by ultra-low voltage

Abstract

The invention discloses a biquad unit for realizing a band-pass filter by ultra-low voltage and belongs to technical field of filters. The biquad unit comprises a first transconductance module, a first differential capacitor, a second transconductance module, a second differential capacitor and a current source module, wherein the first transconductance module is used for receiving an input voltage signal and converting the input voltage signal into a current signal; the first differential capacitor is connected with the first transconductance module to form a first integral unit and used for determining a plural conjugate pole of a biquad unit transmission function; the second transconductance module is used for receiving an output voltage signal and converting the output voltage into the current signal; the second differential capacitor is connected with the first transconductance module and the second transconductance module to form a second integral unit and used for determining the plural conjugate pole of the biquad unit transmission function; and the current source module is connected with the first transconductance module and used for providing branch current of the biquad unit. The biquad unit has simple structure and is easy to realize, effectively reduces the complexity and the power consumption of a band-pass filter circuit structure and realizes the ultra-low power supply voltage.

Description

technical field [0001] The invention relates to the technical field of filters, in particular to a biquad unit for realizing a band-pass filter with ultra-low voltage. Background technique [0002] The filter was first proposed by Americans and Germans in 1915. Today, filter theory and technology have been continuously improved and innovated. Filtering is actually a frequency selection process, and a filter is a frequency selection network that processes an input signal at a specific frequency to obtain a desired output signal. According to the time-domain characteristics of the input signal, filters can be divided into analog filters and digital filters. Due to the outstanding characteristics of fast processing speed, simple circuit structure, and low power consumption, analog filters are widely used in various electronic devices. [0003] Among many realization methods of analog filter, the cascade design method is widely adopted because of its simple realization. The ...

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Problems solved by technology

However, the current biquad unit has the following disadvantages: First, the fully differential biquad unit of the filter with the traditional transconductance-capacitance structure needs to use four transconductance amplifiers, and each transconductance amplifier uses multiple transistors, At the same time, an additional common-mode feedback circuit is required to stabilize the output common-mode voltage, which increases the complexity and power consumption of the circuit; secondly, although the filter with a new structure reduces the complexity of the circuit, due to the excess voltage consumed by the laminated transistor The degree is large, it is difficult to reduce the power supply voltage below 1V, and its minimum operating voltage is equal to four overdrive voltage V dsat plus two threshold voltages V TH , so it is difficult to meet the chip's requirements for low power supply voltage

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