Electronically controlled voltage mode first order multifunction filter using low-voltage low-power bulk-driven OTAs

In this paper, a new versatile voltage mode first order filter using low-voltage low-power bulk-driven OTAs is presented. The proposed filter with two high impedance input-voltage nodes and single output-voltage node consists of two OTAs, one grounded capacitor and one grounded resistor. Three filtering responses, low-pass (LP), high-pass (HP) and all-pass (AP) are obtained by appropriately applying the input signal into the input nodes. The natural frequency (ω0) can be electronically tuned by the bias current. In case of all-pass filter, its phase response is electronically controlled by adjusting only single bias current. With this feature, it doesn't need to simultaneously change two bias currents or two passive element values. The performances of the proposed filter were evaluated via PSPICE simulations using CMOS 0.18 μm TSMC technology parameters (level 7) with ±0.4 V supply voltages. The proposed filter consumes 47.2 μW. To obtain the actual testing results, the proposed filter was also experimented using commercially available IC, LM13700. Moreover, the three phases sinusoidal oscillator based on proposed first order high-pass filter was designed and investigated by PSPICE simulation and experiment.