Design of folded cascode op amp and its application – bandgap reference circuit

Circuit World ◽  
2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Roohie Kaushik ◽  
Jasdeep Kaur ◽  
Anushree Anushree
Keyword(s):  
Circuit Design ◽  
Digital Circuit ◽  
Reference Voltage ◽  
Design Flow ◽  
Slew Rate ◽  
Content Type ◽  
Op Amp ◽  
Complete Study ◽  
Folded Cascode ◽  
Multiplier Circuit

Purpose Reference voltage or current generators are an important requirement for an analog or digital circuit design. Bandgap reference circuits (BGR) are most common way of generating the reference voltage. This paper aims to provide a detailed insight of design of a folded cascode operational amplifier (FC op amp) and a BGR circuit. The complete study flow from design to layout of the circuits on 180 nm semiconductor laboratory (SCL) process leading to bonding diagram for possible tape-out is discussed. This study work has been supported by MeitY, Govt. of India, through Special Manpower Development Project Chip to System Design. Design/methodology/approach This paper provides a detailed insight in design of a FC op amp and a BGR circuit. The complete study flow from design to layout of the two circuits on 180 nm SCL process leading to bonding diagram for possible tape-out is discussed. Section 2 shows the design of FC op amp, beta-multiplier circuit and their simulation results. Section 3 describes the comparison of design of conventional BGR and the proposed BGR with other state-of-art BGR circuits. Section 4 gives the comparison of their performance. The conclusion is given in Section 5. Findings The post-layout simulation of FC op amp show an open-loop gain of 64.5 dB, 3-dB frequency of 5.5 KHz, unity-gain bandwidth of 8.7 MHz, slew rate of 8.4 V/µs, CMRR of 111 dB and power of 25.5µW. Among the two BGR designs, the conventional BGR generated 693 mV of reference voltage with a temperature coefficient of 16 ppm/°C the other BGR, with curvature correction generated 1.3 V of reference voltage with a temperate coefficient of 6.3 ppm/°C , both results in temperature ranging from −40°C to 125°C. The chip layout of the circuits designed on 180 nm SCL process ensures design rule check (DRC), Antenna and layout versus schematic (LVS) clean with metal fill. Research limitations/implications Slew rate, stability analysis, power are important parameters which should be taken care while designing an op amp for a BGR. Direct current gain should be kept higher to reduce offset errors. Input common mode range is decided by the operating temperature range. A higher power supply rejection ratio will reduce BGR sensitivity to supply voltage variations. Input offset should be kept low to reduce BGR error in reference voltage. However, this paper emphasis on the flow from schematic to layout using simulation tools. As part of the study, the bonding diagram for tape-out of BGR and FC design in the given SCL frame size with seal ring is also explored, for possible tape-out. Practical implications Reference voltage or current generators are an important requirement for an analog or digital circuit design. BGR are most common way of generating the reference voltage. This paper provides a detailed insight in design of a FC op amp and a BGR circuit. The complete study flow from design to layout of the circuits on 180 nm SCL process leading to bonding diagram for possible tape-out is discussed. The chip layout of the circuits was designed on 180 nm SCL process ensuring DRC, antenna and LVS clean with metal fill using Cadence virtuoso and Mentor Graphics Calibre simulation tools. Social implications BGR are most common way of generating the reference voltage. This paper gives a detailed insight of a BGR design using a folded-cascode operational amplifier. The FC op amp is biased using a beta multiplier circuit and high-swing cascode current mirror circuit. The paper discuss FC circuit design flow from schematic to layout. Originality/value FC op amp is biased using a beta multiplier circuit and high-swing cascode current mirror. The paper discusses FC design flow from schematic to layout. The circuits were designed on 180 nm SCL technology with 1.8 V of power supply. The post-layout simulation show an open-loop gain of 64.5 dB, 3 dB frequency of 5.5 KHz, unity-gain bandwidth of 8.7 MHz, slew rate of 8.4 V/µs, CMRR of 111 dB and power of 25.5 µW. BGR were designed using FC op amp. The proposed BGR generated 1.3 V of reference voltage with a temperature coefficient of 6.3 ppm/°C in the range from −40°C to 125°C in schematic simulation.

A 1-mm2 CMOS-pipelined ADC with integrated folded cascode operational amplifier

2020 ◽  
Vol 37 (4) ◽  
pp. 205-213
Author(s):  
Norhamizah Idros ◽  
Zulfiqar Ali Abdul Aziz ◽  
Jagadheswaran Rajendran
Keyword(s):  
Operational Amplifier ◽  
Open Loop ◽  
Cmos Process ◽  
Silicon Area ◽  
Content Type ◽  
Op Amp ◽  
Dc Gain ◽  
Input Range ◽  
Folded Cascode ◽  
The Impact

Purpose The purpose of this paper is to demonstrate the acceptable performance by using the limited input range towards lower open-loop DC gain operational amplifier (op-amp) of an 8-bit pipelined analog-to-digital converter (ADC) for mobile communication application. Design/methodology/approach An op-amp with folded cascode configuration is designed to provide the maximum open-loop DC gain without any gain-boosting technique. The impact of low open-loop DC gain is observed and analysed through the results of pre-, post-layout simulations and measurement of the ADC. The fabrication process technology used is Silterra 0.18-µm CMOS process. The silicon area by the ADC is 1.08 mm2. Findings Measured results show the differential non-linearity (DNL) error, integral non-linearity (INL) error, signal-to-noise ratio (SNR) and spurious-free dynamic range (SFDR) are within −0.2 to +0.2 LSB, −0.55 LSB for 0.4 Vpp input range, 22 and 27 dB, respectively, with 2 MHz input signal at the rate of 64 MS/s. The static power consumption is 40 mW with a supply voltage of 1.8 V. Originality/value The experimental results of ADC showed that by limiting the input range to ±0.2 V, this ADC is able to give a good reasonable performance. Open-loop DC gain of op-amp plays a critical role in ADC performance. Low open-loop DC gain results in stage-gain error of residue amplifier and, thus, leads to nonlinearity of output code. Nevertheless, lowering the input range enhances the linearity to ±0.2 LSB.

Digital Circuit Design Challenges and Opportunities in the Era of Nanoscale CMOS

2008 ◽  
Vol 96 (2) ◽  
pp. 343-365 ◽  
Author(s):  
B.H. Calhoun ◽  
Yu Cao ◽  
Xin Li ◽  
Ken Mai ◽  
L.T. Pileggi ◽  
...  
Keyword(s):  
Circuit Design ◽  
Digital Circuit ◽  
Nanoscale Cmos ◽  
Digital Circuit Design ◽  
Challenges And Opportunities ◽  
Design Challenges

Consumer attitudes towards bloggers and paid blog advertisements: what’s new?

2018 ◽  
Vol 36 (7) ◽  
pp. 778-793 ◽  
Author(s):  
Patrick van Esch ◽  
Denni Arli ◽  
Jenny Castner ◽  
Nabanita Talukdar ◽  
Gavin Northey
Keyword(s):  
Online Survey ◽  
Consumer Attitudes ◽  
Design Flow ◽  
Personal Contact ◽  
Purchase Intent ◽  
Online Retail ◽  
Content Type ◽  
Perceived Trust ◽  
Segmentation Strategy ◽  
Consumer Skepticism

Purpose Reports show that 6.77m people published blogs on blogging websites and more than 12m people write blogs using their social network. However, few studies have explored consumer attitudes toward bloggers and their advertising. Therefore, an effort to discover how paid blog advertisements influence consumer attitudes toward bloggers and the products they advertise will help marketers gain an understanding of how to use bloggers as paid sponsors to influence consumer purchase intent. Using online survey approach, a study recruited participants (n=210) through an online survey platform (MTurk). The results indicated that the similarity between the consumer and the ad creator is an important psychological reason why consumers are more likely to perceive advertisements as more authentic, more affective, less deceptive and more credible, and they are thus more likely to trust the blogger. On the other hand, the importance of ad attribute (authenticity) does not significantly influence consumers’ intention to purchase products advertised by a blogger. As consumers are becoming more skeptical of advertisements, blogs need to be entertaining and a pleasure to view. Not only does the content need to be interesting, the design, flow and clarity of the blogs must also be considered important factors. In addition, advertising needs to be believable, credible and honest. In the online world, trust and credibility are still paramount in attracting consumers’ engagement; hence, promoting companies’ products and services through blogs can be an effective strategy to lower consumer skepticism barriers. The paper aims to discuss these issues. Design/methodology/approach Participants answered questions about their attitudes toward bloggers and their advertising when purchasing products in an online retail environment. Furthermore, participants also answered questions about their perceived trust in the bloggers themselves as well as the authenticity and credibility of the brand-related communication received from bloggers. Moreover, they reported on their attitudes toward how deceptive they considered bloggers and their advertising to be. Finally, participants reported how paid blog advertisements influence their purchase intent. Findings Similarity toward the ad creator is an important psychological reason behind consumers’ attitude toward blogs. Consumers who follow a blog often have the same interests and are thus more likely to support bloggers. This idea can be used as a segmentation strategy to reach particular consumers. Consumers who perceive similarity with the ad creator are more likely to recognize the ads as more authentic, affective, credible and trustworthy as well as less deceptive, regarding the blogger. Blogs need to be entertaining and a pleasure to view. Not only does the content need to be interesting but the design, flow and clarity of the blog are also important factors. Blog advertising needs to be believable, credible and honest. In the online world, trust and credibility are still paramount in attracting consumers’ engagement with the website, bloggers or social media. Originality/value Trust in the blogger did not influence consumers’ purchase intent; however, it did influence their attitude toward how similar they are with the blogger. In an online shopping environment, the human touch and personal contact between consumers and retailers has been lost. Consumers often leave the online transaction due to a lack of trust. Therefore, bloggers can be replacements for the missing “salesperson” in online interactions. Companies can use bloggers as the mediating person to reach their intended audiences, bridging the gap between the company and consumers.

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