Digital tuning circuit for RC (resistor-capacitor) filter

Abstract

The invention discloses a digital tuning circuit for an RC (resistor-capacitor) filter and relates to the technical field of impedance networks. The digital tuning circuit comprises an integrator circuit and a window comparator circuit; the integrator circuit for producing a periodic digital waveform comprises PMOS (P-channel metal oxide semiconductor) transistors M1-M4, an NMOS (N-channel metal oxide semiconductor) transistor M5, NMOS transistors M7 and M8, a capacitor C, a programmable switch resistor array Rref and an error amplifier U1. The window comparator circuit comprises comparators U2 and U3. Compared with the prior art, the digital tuning circuit is simple in structure, easy to implement, low in power consumption and high in tuning precision; especially for low-frequency and multimode filters, chip area is greatly reduced, and cost is greatly reduced accordingly; the digital tuning circuit is widely applicable to on-chip active filters in the fields such as electronics and communication.

Description

technical field [0001] The invention relates to the technical field of impedance networks, in particular to an RC filter digital tuning circuit. Background technique [0002] In order to satisfy channel selection and adjacent channel suppression, the filter must have an accurate cut-off frequency, and in the circuit manufacturing process, due to the influence of process deviation and ambient temperature, the deviation between the resistance and capacitance in the circuit and the design value is large, up to ±40 % frequency variation range, in order to control it in the range of ±3%, a tuning circuit must be introduced. Tuning circuits are generally divided into active tuning and passive tuning. Due to the poor linearity of active tuning, passive tuning circuits are generally used, and passive tuning circuits are divided into resistance tuning and capacitance tuning. In actual circuits, although the frequency performance of capacitors is better than that of resistors under t...

AI Technical Summary

Problems solved by technology

In actual circuits, although the frequency performance of capacitors is better than that of resistors under the same precision conditions, for low-frequency and multi-mode filters, larger capacitors are required under the condition of ensuring noise, which greatly increases the chip area.

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