High Input Impedance Single-Resistor Tuned Variable-gain Allpass Filter with Low Phase-error

Two new single-CFA first-order allpass filter configurations are presented wherein the gain and phase-response is tunable by single resistor. The filter phase-error (θ
e
) as caused by the device parasitic capacitors (C
y,z
), are shown to be extremely low with appropriate design. Effects of roll-off characteristics of the port coefficients and parasitic components of the CFA are analysed. Filter response and it’s in extension the implemented oscillators have been satisfactorily substantiatedwith simulation, along with hardware experiments, covering a pole-frequency range of 1 ≤ f
o
(MHz) ≤ 9.6.