A Biasing Approach to Design Ultra-Low-Power Standard-Cell-Based Analog Building Blocks for Nanometer SoCs

Abstract

Date of publication xxxx 00, 0000, date of current version xxxx 00, 0000.

A Novel Differential to Single-Ended Converter for Ultra-Low-Voltage Inverter-Based OTAs

“…The same kind of differential to single-ended conversion is needed also in inverter-based or standard-cell-based OTAs exhibiting a differential input and a single-ended output. In recent research works dealing with inverter-based analog circuits such as [6], [7], [11], [29], [30], the differential to single-ended conversion is often performed exploiting the circuit topology depicted in Fig. 1.…”

“…The Verilog netlist has been imported in the Cadence Innovus environment, together with all the technology files needed in the conventional place and route flow usually adopted for digital circuits. A conventional place and route flow (without timing constraints) including design import, floorplanning, place, and routing has then been carried out exploiting the same scripts conventionally adopted to implement digital circuits as in [29]. The automatically generated layout is depicted in Fig.…”

“…In fact, the most common practice to design standard-cellbased analog functions is to exploit the inverter gate, taken from a standard-cell library, as a basic analog amplifier. Focusing on the inverter-based implementation of OTAs with differential input and single-ended output, the differential to single-ended (D2S) converter play a main role [3], [11], [29]; indeed its performance directly affects the overall commonmode rejection ratio (CMRR) and input common-mode range (ICMR) of the whole OTA. In recent literature [29], [30], inverter-based OTAs rely on a D2S topology based on an inverter driving another inverter with the input and output tight together which behaves as a "diode" connected device to implement a voltage gain approximately equal to −1.…”

“…Focusing on the inverter-based implementation of OTAs with differential input and single-ended output, the differential to single-ended (D2S) converter play a main role [3], [11], [29]; indeed its performance directly affects the overall commonmode rejection ratio (CMRR) and input common-mode range (ICMR) of the whole OTA. In recent literature [29], [30], inverter-based OTAs rely on a D2S topology based on an inverter driving another inverter with the input and output tight together which behaves as a "diode" connected device to implement a voltage gain approximately equal to −1. However, since this approach is based on the matching of the inverters, the performance of this D2S results sensitive to PVT variations if the bias point of the inverters is not properly stabilized.…”

“…However, since this approach is based on the matching of the inverters, the performance of this D2S results sensitive to PVT variations if the bias point of the inverters is not properly stabilized. To overcome this issue, in [29] a body-bias strategy to set the static output voltage and the bias current of inverters has been proposed; however this approach requires ad-hoc circuits whose supply voltage is larger than the one of the ULV OTA. Recently a similar replica-bias approach to set the output static voltage of the basic amplifier cells has been presented in [31].…”