scholarly journals Right-direct (BI) type wide bandpass SC ladder filter with compensation for finite amplifier gain and offset voltage

2008 ◽  
Vol 21 (2) ◽  
pp. 233-241
Author(s):  
Nikolay Radev ◽  
Kantcho Ivanov ◽  
Kalin Stanchev
Keyword(s):  
Sixth Order ◽  
Operational Amplifiers ◽  
Switched Capacitor ◽  
Offset Voltage ◽  
Op Amps ◽  
Dc Gain ◽  
Amplifier Gain

In this paper gain- and offset-compensated (GOC) modification of a sixth-order right-direct (BI) type wide bandpass switched-capacitor (SC) ladder filter is proposed. It is based on the use of simple and fast operational amplifiers (op amps) with low but precisely known and stable dc gain A. At first, the conventional integrators in the filter are replaced with GOC integrators and the unswitched capacitors in the capacitive loops are split into two capacitors. Subsequently, the nominal op amps gain value A0 is taking into account in the capacitance sizing of some appropriately chosen capacitors. .

scholarly journals A comparative analysis of two gain- and offset-compensated switched-capacitor integrators

2002 ◽  
Vol 15 (2) ◽  
pp. 295-305
Author(s):  
Nikolay Radev ◽  
Kantcho Ivanov
Keyword(s):  
High Performance ◽  
Building Blocks ◽  
Switched Capacitor ◽  
Central Frequency ◽  
High Q ◽  
Offset Voltage ◽  
Dc Gain ◽  
Band Pass ◽  
Analytical Expressions ◽  
The Ideal

Two high-performance switched-capacitor (SC) integrators which use different approaches for the compensation of the operational amplifier finite dc gain and offset voltage are considered. Analytical expressions for the gain, phase and offset voltage errors of the Baschirotto-90 integrator are derived and compared with the corresponding errors of the Shafeeu-91 integrator. Both the integrators are used as building blocks of a high-Q band pass SC biquad. The resultant filters are compared in terms of the percent deviations from the ideal case of the central frequency and the quality factor. Subsequently, the slight shift in the frequency response of the biquad with Shafeeu-91 integrator is eliminated by modifying the values of two capacitors .

Switched-Capacitor Common-Mode Feedback-Based Fully Differential Operational Amplifiers and its Usage in Implementation of Integrators

2020 ◽  
Vol 29 (14) ◽  
pp. 2050223
Author(s):  
Joydeep Basu ◽  
Pradip Mandal
Keyword(s):  
Continuous Time ◽  
High Gain ◽  
Design Guidelines ◽  
Operational Amplifiers ◽  
Switched Capacitor ◽  
Common Mode ◽  
Fully Differential ◽  
Op Amp ◽  
Dc Gain ◽  
Minimum Power Consumption

For stabilizing the common-mode output voltage of fully differential operational amplifiers, switched-capacitor (SC) type of common-mode feedback (CMFB) is a familiar technique. This is appropriate for implementing high-gain wide-swing low-power op-amps due to its benefits of minimum power consumption, superior linearity across a large amplifier output swing range, and improved feedback loop stability in comparison to continuous-time CMFB. However, the usage of SC-CMFB requires careful attention to some realistic aspects, details of many of which are available in literature. Nonetheless, its adverse effect on the op-amp’s differential-mode gain has not been investigated much. The explanation for this effect is the SC-CMFB-induced equivalent resistive loading, and this is particularly significant in amplifiers like folded cascode which are intended to provide a high gain. This issue of drop in op-amp dc gain because of SC-CMFB, and the consequence on the realization of continuous-time and discrete-time forms of integrators utilizing such amplifiers is the topic of discussion in this paper. Relevant analytical derivations and circuit simulations at the transistor level are provided. A couple of design guidelines and circuit topologies for minimizing the loading-induced gain reduction are also presented.

Improvement of Gain Accuracy and CMRR of Low Power Instrumentation Amplifier Using High Gain Operational Amplifiers

2020 ◽  
Vol 12 (3) ◽  
pp. 168-174
Author(s):  
Rashmi Sahu ◽  
Maitraiyee Konar ◽  
Sudip Kundu
Keyword(s):  
Low Power ◽  
Building Blocks ◽  
High Gain ◽  
The Other ◽  
Operational Amplifiers ◽  
Instrumentation Amplifier ◽  
Biomedical Signals ◽  
Op Amp ◽  
Op Amps ◽  
Multi Stage

Background: Sensing of biomedical signals is crucial for monitoring of various health conditions. These signals have a very low amplitude (in μV) and a small frequency range (<500 Hz). In the presence of various common-mode interferences, biomedical signals are difficult to detect. Instrumentation amplifiers (INAs) are usually preferred to detect these signals due to their high commonmode rejection ratio (CMRR). Gain accuracy and CMRR are two important parameters associated with any INA. This article, therefore, focuses on the improvement of the gain accuracy and CMRR of a low power INA topology. Objective: The objective of this article is to achieve high gain accuracy and CMRR of low power INA by having high gain operational amplifiers (Op-Amps), which are the building blocks of the INAs. Methods: For the implementation of the Op-Amps and the INAs, the Cadence Virtuoso tool was used. All the designs and implementation were realized in 0.18 μm CMOS technology. Results: Three different Op-Amp topologies namely single-stage differential Op-Amp, folded cascode Op-Amp, and multi-stage Op-Amp were implemented. Using these Op-Amp topologies separately, three Op-Amp-based INAs were realized and compared. The INA designed using the high gain multistage Op-Amp topology of low-frequency gain of 123.89 dB achieves a CMRR of 164.1 dB, with the INA’s gain accuracy as good as 99%, which is the best when compared to the other two INAs realized using the other two Op-Amp topologies implemented. Conclusion: Using very high gain Op-Amps as the building blocks of the INA improves the gain accuracy of the INA and enhances the CMRR of the INA. The three Op-Amp-based INA designed with the multi-stage Op-Amps shows state-of-the-art characteristics as its gain accuracy is 99% and CMRR is as high as 164.1 dB. The power consumed by this INA is 29.25 μW by operating on a power supply of ±0.9V. This makes this INA highly suitable for low power measurement applications.

Technique for offset voltage cancellation in MOS operational amplifiers

1985 ◽  
Vol 21 (9) ◽  
pp. 389 ◽  
Author(s):  
S.L. Wong ◽  
C.A.T. Salama
Keyword(s):  
Operational Amplifiers ◽  
Offset Voltage
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