Analog IC design project

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Answered Same Day Dec 01, 2019

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David answered on Dec 27 2019

135 Votes

FULLY-DIFFERENTIAL HIGH-SPEED AND HIGH-PRECISION OPERATIONAL AMPLIFIER DESIGNS
1. INTRODUCTION
- (Project circuit diagram)
For continuous analog applications as shown in figure, a fully-differential high-speed and high- precision amplifier with a gain of 4 will be developed. In this work, gain-boosting folded- cascode operational amplifiers (OTAs) is designed with a power budget of 10mW and aims to minimize the large-signal settling time to 0.5 % accuracy. It must be noticed that supply voltage is of the order of 1.8 V.
It is important to understand the basic concept of OTA. OTA i.e. Operational Transconductance Amplifiers are the most important blocks for various analog type systems and circuits. Actually, the best suited design component for OTA is the CMOS devices which has very less power requirements. The similar technology has been utilized in the fully differential high speed and high precision operational amplifier designs.
From the simplified OTA model with one dominant pole and dc gain, the target gain and unity-gain bandwidth of an OTA can be approximately achieved in order to meet less than 1 percent gain e
or with 25ns settling time limitations. Thus, pulling out additional gain, our initial target OTAs are determined as gain-boosting folded-cascode OTAs.
Generally, single-stage OTAs are likely to suffer the bottleneck of maximum dc gain at certain boundary, which is not for multi-stage OTAs. Single stage OTAs actually holds the trade-off between power with gain-bandwidth (GBW), not gain itself. If we increase the bias cu
ent with fixed bias voltages, it increases the transconducatance (gm); however, at the same time, it decreases the output resistance (rds), which ends up constant gain. It also improves GBW, which is gm/CL with fixed output load capacitance (CL) of the order of 1.5 pF. Thus, we need to separately control gm and rds to improve the gain, separating the bias cu
ents.
2. TECHNOLOGY PARAMETER EXTRACTION
The technology parameters extraction is shown in the below mentioned table. To understand this table, it is very important to have idea about the NMOS and PMOS. NMOS (nMOSFET) is basically a type of MOSFET and NMOS transistor is actually developed from n-type source, drain and from a p type substrate. And PMOS (pMOSFET) is basically a type of MOSFET and actually PMOS...

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