A 300mV-Supply, 2nW-Power, 80pF-Load CMOS Digital-Based OTA for IoT Interfaces

Dynamic and Static Calibration of Ultra-Low-Voltage, Digital-Based Operational Transconductance Amplifiers

“…Focusing on the Operational Transconductance Amplifier (OTA), which is a key building block in most analog sub-systems, several new topologies and design techniques (Figure 1b-g) have been recently devised to enable efficient operation in nanoscale technologies and/or under Ultra-Low-Voltage (ULV) supply [7][8][9][10][11][12][13][14][15][16].…”

“…In general, ULV OTAs can be classified as: gate-driven, bulk-driven, inverter-based, VCO-based and digital-based [15,16] topologies.…”

“…However, they suffer of limited intrinsic gain and common-mode rejection in nanometer-scale technologies. Gate-driven [8,9], (c) Bulk-driven [10] (d,e) Inverter-based [11,12] (f) VCO-based [13,14] (g) Digital-based [16] topologies. ULV OTA state-of-art comparison plots:…”

“…An alternative approach [17][18][19][20][21][22][23][24][25][26][27] aims at the implementation of analog functions by digital means. Leveraging this concept, a VCO-based OTA [28] and a digital-based [15] OTA (DB-OTA), Figure 1f,g, have been recently proposed [13,16]. Both OTAs are based on time-domain information processing and prove to be very good candidates for efficient ULV operation.…”

“…Both OTAs are based on time-domain information processing and prove to be very good candidates for efficient ULV operation. Their operation, however, can be impaired by process variations and mismatch, so that an ad-hoc calibration is required for acceptable yield [16,29]. The design of a calibration network for DB-OTAs is critical since it can possibly impair the versatility and limit the power and area advantage of these solutions.…”