A NOVEL CURRENT-MODE HIGH-FREQUENCY POLYPHASE FILTER USING MULTI-OUTPUT CURRENT DIFFERENCING TRANSCONDUCTANCE AMPLIFIERS

Hao Peng – Chunhua Wang – Xiaotong Tian

   This paper introduces a novel polyphase filter working at high centre frequency using multi-output current differencing transconductance amplifiers (MOCDTAs). The MOCDTA possesses characteristics of low input impedance, high output impedance, wide work frequency and linearly adjustable transconductance. The proposed filter consists of two MOCDTAs, two grounded capacitors, and no resistors. The features of low input impedance and high output impedance make it suitable for cascade. The bandwidth and centre frequency could be adjusted independently by external bias voltage V_C and V_Ca. The image rejection ratio (IRR) could reach 31.6 dB at the centre frequency of 114 MHz, and its bandwidth could be 11.1 MHz. Besides, the centre frequency could be tuned from 38 MHz to 150 MHz with bandwidth of 20.1 MHz. Simulation results which verify the theory are included.

Keywords: current-mode, analogue circuits, polyphase filter, image rejection, independently tunable, MOCDT

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