Abstract
This paper presents a new multiple-input single −output voltage-mode universal biquad filter based on multiple−input operational transconductance amplifiers (MI-OTA). This work demonstrates that the multiple-input OTA−based universal filter can provide more filtering responses and other benefits, compared to conventional OTA−based one. The filter provides electronic and orthogonal control of the natural frequency and the quality factor. Furthermore, a two-phase quadrature oscillator can be obtained by slightly modifying the proposed universal filter while the condition and frequency of oscillation can be controlled orthogonally and electronically. The performance of the proposed circuit is evaluated in Cadence environment using the TSMC $0.18~\mu \text{m}$ CMOS technology. The voltage supply is 1.2 V and the power dissipation of the MI−OTA is $24~\mu \text{W}$ . For 1% third intermodulation distortion (IMD3) the dynamic range of the band−pass filter is 78.6 dB. In addition, the proposed filter and oscillator are investigated through experiment tests using LM13700 commercially available OTA.
Highlights
Analog filters are important signal processing blocks for electronic, communication and control systems applications
This paper presents a new MI−operational transconductance amplifier (OTA) based universal filter, with more filtering responses and more versatility, and a quadrature oscillator
For the filter design the capacitor C1 = C2 = 10 nF and Rset1 = Rset2 = Rset3 = Rset4 = 15 k were selected for natural frequency of 1 kHz
Summary
Analog filters are important signal processing blocks for electronic, communication and control systems applications. The MI−OTAs used in the aforementioned designs were based on parallel connections of differential stages to obtain the multiple-input blocks, resulting in increased number of transistors and chip area, but mainly in increased number of current branches, leading to a higher power dissipation and a more complex internal structure. In order to realize the multiple−input OTA, one could use n single-input OTAs with their outputs connected together, as shown in Fig. 1 (c). This realization results in increased chip area and power consumption that limits its usefulness in low−voltage and low−power applications. PROPOSED CIRCUITS The proposed universal biquad filter using MI−OTAs is shown Fig. 4 It consists of four MI-OTAs and two grounded capacitors.
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