Programmable feedforward linearized CMOS OTA for fully differential continuous‐time filter design

Abstract

SUMMARYIn this paper, a feedforward linearization method for programmable CMOS operational transconductance amplifier (OTA) is described. The proposed circuit technique is developed using simple source-coupled differential pair transconductors, a feedback-loop amplifier for self-adjusting transcoductance (g m ) and a linear reference resistor (R). As a result, an efficient linearization of a transfer characteristic of the OTA is obtained. SPICE simulations show that for 0.35 m AMS CMOS process with a single +3 V power supply, total harmonic distortion at 1 V pp and temperature range from −30 to +90 • C is less than −49.3 dB in comparison with −35.8 dB without linearization. Moreover, the input voltage range of linear operation is increased. Power consumption of the linearized OTA circuit is 0.86 mW. Finally, the OTA is used to design a third-order elliptic low-pass filter in high-frequency range. The cut-off frequency of the operational transconductance amplifier-capacitor (OTA-C) filter is tunable in the range of 322.6 kHz-10 MHz using the feedforward linearized OTAs with the digitally programmable current mirrors.

Design of Sinh‐Domain filters using complementary operators

“…A final comment concerns the effects of parasitics in Sih‐Domain filters. Owing to the fact that the core of both S cells and CCCIIs is the same, it is expected that the results obtained in 1–4 would be also valid for the case in Sinh‐Domain filters.…”

“…Also, continuous‐time resistorless filters with electronic tuning capability of their frequency behavior can be designed using different types of current conveyors (CCIIs), such as multiple output current‐controlled current conveyors (MO‐CCIIs), dual‐x current conveyors, and operational transconductance amplifiers 1–4.…”

“…Present requirement for realizing analog filters with capabilities for low‐voltage operation and electronic adjustment of their frequency characteristics has gained a significant research effort toward these goals 1–16.…”

Monotonic, critical monotonic, and nearly monotonic low‐pass filters designed by using the parity relation for Jacobi polynomials

“…Such networks can be implemented in two ways: with the element replacement method [22,23] and the method of the operational simulation [24,25], or the signal-flow graph approach. Therefore, a tremendous effort has gone into designing various types of filters that retain the excellent performance of the LC ladders without having to build and use inductors.…”

“…Therefore, a tremendous effort has gone into designing various types of filters that retain the excellent performance of the LC ladders without having to build and use inductors. Such networks can be implemented in two ways: with the element replacement method [22,23] and the method of the operational simulation [24,25], or the signal-flow graph approach. On the other hand, the wave digital filters are derived from a resistance terminated LC ladder network in which its sensitivity properties are also excellent in the passband [26].…”