Analysis of OTA‐C filters with weakly nonlinear transconductors

SUMMARY This paper advances the field of externally linear–internally nonlinear (ELIN) filters by introducing a synthesis method that enables the design of high‐order class‐AB sinh filters by means of complementary metal–oxide semiconductor (CMOS) weak‐inversion sinh integrators comprising only one type of devices in their translinear loops. The proposed transistor‐level synthesis approach is demonstrated through the examples of (1) a biquadratic and (2) a fifth‐order filter, and their simulated performance is studied. The biquadratic filter achieves a dynamic range of 94 dB and has a tunable quality factor Q up to the value of 8, whereas its natural frequency can be tuned for four orders of magnitude. Its static power consumption amounts to 6.2 μW for Q = 1 and fo = 2 kHz. The fifth‐order Chebyshev sinh CMOS filter with a cut‐off frequency of 100 Hz, a pass band ripple of 1 dB, and a power consumption of ~300 nW is compared head‐to‐head with its pseudo‐differential class‐AB CMOS log domain counterpart. The sinh filter achieves similar or better signal‐to‐noise ratio (SNR) and signal‐to‐noise‐plus‐distortion ratio (SNDR) performances with half the capacitor area but at the expense of higher power consumption from the same power supply level. All three presented filter topologies are novel. Cadence design framework simulations have been performed using the commercially available 0.35 µm AMS (austriamicrosystems) process parameters. Copyright © 2013 John Wiley & Sons, Ltd.

Section: Simulated Resultsmentioning

confidence: 99%

A simulation study of high‐order CMOS hyperbolic‐sine filters

Kardoulaki

Glaros

Katsiamis

et al. 2013

“…OTAs are widely used in active filter design [11,14,19,21,22,34]. In particular, the OTA topology described in Section 3 is very suited to build continuous-time filters where the amplifiers are connected in non-inverting configuration, thanks to its wide input CM swing capability.…”

Section: Design Example: Second-order Ota-c Lowpass Filtermentioning

confidence: 99%

On the input common‐mode voltage range of CMOS bulk‐driven input stages

Carrillo

Torelli

Dominguez

et al. 2011

SUMMARYIn this paper the response of a bulk-driven MOS Metal-Oxide-Semiconductor input stage over the input common-mode voltage range is discussed and experimentally evaluated. In particular, the behavior of the effective input transconductance and the input current is studied for different gate bias voltages of the input transistors. A comparison between simulated and measured results, in standard 0.35- §m CMOS Complementary Metal-Oxide-Semiconductor technology, demonstrates that the model of the MOS transistors is not sufficiently accurate for devices operating under forward bias conditions of their sourcebulk pn junction. Therefore, the fabrication and the experimental evaluation of any solution based on this approach are highly recommended. A technique to automatically control the gate bias voltage of a bulk-driven differential pair is proposed to optimize the design tradeoff between the effective input transconductance and the input current. The proposed input stage was integrated as a standalone block and was also included in a 1.5-V second-order operational transconductance amplifier (OTA)-C lowpass filter. Experimental results validate the effectiveness of the approach.

“…However, it can be observed that while offering low noise, its large signal characteristics are extremely nonlinear. Therefore, the dynamic range and the efficiency of the differential pair using MOS transistors are limited [5,[19][20][21]. A number of techniques for improving the linear properties of CMOS transconductance elements based on the source-coupled differential pairs have been proposed [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38].…”

Section: Introductionmentioning

confidence: 99%

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

Szczepański

Pankiewicz

Koziel

2009

Self Cite

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.