A design and analysis of a voltage-mode first order allpass filter using the voltage differencing current conveyor (VDCC) is proposed in this paper. The synthesis of the proposed allpass filter is based on the connection of the voltage-mode lossy integrator and voltage-mode subtraction with single VDCC, single grounded capacitor and two resistors. The proposed filter is simple structure and grounded capacitor is attractive for integrated circuit implementation. The proposed circuit doesn’t use the active building block with multiple output current output terminal which is easy the design by using commercially available IC. The phase response of the proposed first order allpass filter is electronically tuned via the DC bias current of VDCC. The proposed filter doesn’t require the matching condition for simultaneously adjusting two parameters to control the phase response. The simulation results of the proposed filter are based upon the TSMC 0.18 m CMOS process and ±0.9V supply voltages.
Słowa kluczowe: VDCC; Allpass filter; Electronic controllability.
Przedstawiono projekt i analizę filtru pierwszego rzędu wykorzystującego układ VDCC, uziemiona pojemność i dwa rezystory. Odpowiedź fazowa jest łatwa do strojenia za pośrednictwem prądu.
Keywords: układ VDCC (voltage differencing current conveyor), filtr pierwszego rzędu
The first-order allpass filter or well-known as phase shifter circuit is utilized to delay the sinusoidal output phase from the sinusoidal input phase with equal magnitude of the output signal for all operational frequency. For the first order allpass system, the phase of output waveform can be shifted from - 180 to 0 or from 0 to 180. It is also called as the phase shifter circuit. This filter is important in many analog signal processing systems for examples communication system, measurement and instrument system, biomedical system etc.  There has been continuous increase in the design of electronic circuit using the active building block [2-8]. The well-known active building blocks are OPAMP, OTA and CCII. These active elements offer the flexibility and convenience to design the circuit by using minimum component count. The voltage differencing current conveyor (VDCC)  is interesting active element. It is electronically controllable active building block, where its transconductance gain (gm) can be adjusted via DC bias current. The VDCC based circuits have been introduced in the open literature. These circuits include sinusoidal waveform generator [10-13], capacitance multiplier , second order multifunction filter [15-18], inductance simulator [9, 19-20], ladder filter  and first order filter [22-23]. The first-order voltage-mode filter using z-copy controlled gain voltage differencing current conveyor (ZC-CGVDCC) is presented in . The circuit comprises single ZC-CGVDCC and single grounded capacitor. The phase variation is electronically adjusted. However, this first-order filter requires the active building block with multiple output current terminals. Also, the internal construction of ZCCGVDCC looks complicated. Various first-order allpass filters using z-copy voltage differencing current conveyor (ZC-VDCC) are proposed in . These circuits contain current-mode, m [...]
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