HIGH-ORDER MULTIPLE-MODE AND TRANSADMITTANCE-MODE OTA-C UNIVERSAL FILTERS

Abstract

This paper presents two new high-order OTA-C universal filters. The first proposed filter structure employs n + 3 operational transconductance amplifiers (OTAs) and n grounded capacitors, which can realize nth-order multiple-mode (including voltage, current, transadmittance, and transimpedance modes) universal filtering responses (lowpass, highpass, bandpass, bandreject, and allpass) from the same topology. Since the OTA has high input and output impedances, it is very suitable for transadmittance-mode circuit applications. Therefore, a new high-order transadmittance-mode OTA-C universal filter structure using the minimum components is introduced. The second proposed filter structure uses only n + 1 OTAs and n grounded capacitors, which are the minimum components necessary for realizing nth-order transadmittance-mode universal filtering responses (lowpass, highpass, bandpass, bandreject, and allpass) from the same topology. This represents the attractive feature from chip area and power consumption point of view. Moreover, the two new OTA-C universal filters still enjoy many important advantages: no need of extra inverting or double-type amplifiers for special input signals, using only n grounded capacitors, no need of any resistors, cascadably connecting the former voltage-mode stage and the latter current-mode stage, and low sensitivity performance. H-Spice simulations with TSMC 0.35 μm process and ±1.65 V supply voltages are included and confirm the theoretical predictions.