Abstract
A simple on-chip automatic frequency tuning circuit is proposed. The tuning circuit is modified from voltage-controlled filter (VCF) frequency tuning circuit. We utilize an operational transconductance amplifier and a capacitor to from a single-time constant (STC) circuit which can produce a controllable delay time clock to tune the frequency of the filter. It can efficiently reduce the deviations in the 3 dB bandwidth from the variations of PVT (Process, Voltage and Temperature). The design of the STC circuit is simpler than VCF and it has less chip area. The chip has been implanted using TCMC 0.35 μm CMOS technology and the power consumption is less than 9.05 mW.
Highlights
Analog continuous-time filters [1] are popular in various application, such as video and audio signal processing, ADC, mobile phone, hard disk reading channels, CD- ROM, etc
The tuning circuit is modified from voltage-controlled filter (VCF) frequency tuning circuit
We utilize an operational transconductance amplifier and a capacitor to from a single-time constant (STC) circuit which can produce a controllable delay time clock to tune the frequency of the filter
Summary
Analog continuous-time filters [1] are popular in various application, such as video and audio signal processing, ADC, mobile phone, hard disk reading channels, CD- ROM, etc. The Gm-C filters have higher frequency and flexibility than other analog filter types. Their performances vary with process and environment variations. Many kinds of frequency automatic-tuning methods are derived from phase locked loop (PLL) for analog filters, such as sinusoidal oscillator based PLL tuning circuit, voltage-controlled filter (VCF) tuning circuit and etc [1,5,6,13]. As to the voltage-controlled filter tuning circuit, the power consumption is high and the reference clock needs to be a pure sine wave. We try to make the tuning circuit have following advantages: simplicity, small chip area, good matching with the filter and less power consumption.
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