A low-output-impedance fully differential op amp with large output swing and continuous-time common-mode feedback

1991 ◽  
Vol 26 (12) ◽  
pp. 1825-1833 ◽  
Author(s):  
J.N. Babanezhad
Keyword(s):  
Continuous Time ◽  
Output Impedance ◽  
Common Mode ◽  
Fully Differential ◽  
Op Amp ◽  
Output Swing ◽  
Large Output

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.

Design of a New Low Power Fully Differential Amplifier with Settling Time Enhancement Characteristics

2015 ◽  
Vol 24 (06) ◽  
pp. 1550078 ◽  
Author(s):  
Seid Jafar Hosseinipouya ◽  
Farhad Dastadast
Keyword(s):  
High Performance ◽  
Settling Time ◽  
Cmos Process ◽  
Output Stage ◽  
Common Mode ◽  
Class Ab ◽  
Fully Differential ◽  
Op Amp ◽  
Transconductance Amplifier ◽  
Adaptive Biasing

High performance of fully differential operational transconductance amplifier is designed and implemented using a 0.18-μm CMOS process. The implemented op-amp uses common mode feedback (CMFB) circuit operating in weak inversion region which does not affect other electrical characteristics due to eliminating common mode (CM) levels automatically leading to improve CM rejection ratio (CMRR) of the amplifier significantly. Moreover, the output stage has class-AB operation so that its current can be made larger due to increasing the output current dynamically using adaptive biasing circuit. Additionally, the AC currents of the active loads have been significantly reduced using negative impedances to increase the gain of the amplifier. The results show the GBW 2.3 MHz, slew rate 2.6 V/μs and 1% settling time 150 ns with a capacitive load of 15 pF. This amplifier dissipates only 6.2 μW from a 1.2 V power supply.

A 0.5 V class AB quasi FGMOS pseudo fully differential CMOS op-amp with rail-to-rail input/output swing

2011 ◽  
Author(s):  
Thawatchai Thongleam ◽  
Apirak Suadet ◽  
Arnon Kanjanop ◽  
Pratchayaporn Singhanath ◽  
Buncha Hirunsing ◽  
...  
Keyword(s):  
Input Output ◽  
Class Ab ◽  
Fully Differential ◽  
Op Amp ◽  
Rail To Rail ◽  
Output Swing

Common Mode Feedback Circuits for Low Voltage Fully-Differential Amplifiers

2016 ◽  
Vol 25 (10) ◽  
pp. 1650124 ◽  
Author(s):  
S. Rekha ◽  
T. Laxminidhi
Keyword(s):  
Power Supply ◽  
Continuous Time ◽  
Efficient Solution ◽  
Low Voltage ◽  
Cmos Technology ◽  
Common Mode ◽  
Power Efficient ◽  
Differential Amplifiers ◽  
Fully Differential ◽  
Simulation Results

Continuous time common mode feedback (CMFB) circuits for low voltage, low power applications are proposed. Four circuits are proposed for gate/bulk-driven pseudo-differential transconductors operating on sub-1-V power supply. The circuits are validated for a bulk-driven pseudo-differential transconductor operating on 0.5[Formula: see text]V in 0.18[Formula: see text][Formula: see text]m standard CMOS technology. Simulation results reveal that the proposed CMFB circuits offer power efficient solution for setting the output common mode of the transconductors. They also load the transconductor capacitively offering capacitance of about 1[Formula: see text]fF to tens of femto farads.

A FAST AND LOW SETTLING ERROR CONTINUOUS-TIME COMMON-MODE FEEDBACK CIRCUIT BASED ON DIFFERENTIAL DIFFERENCE AMPLIFIER

2014 ◽  
Vol 23 (05) ◽  
pp. 1450065 ◽  
Author(s):  
TOHID MORADI KHANESHAN ◽  
SAEED NAGHAVI ◽  
MOJDE NEMATZADE ◽  
KHAYROLLAH HADIDI ◽  
ADIB ABRISHAMIFAR ◽  
...  
Keyword(s):  
Continuous Time ◽  
High Speed ◽  
Cmos Technology ◽  
Common Mode ◽  
Op Amp ◽  
Wide Range ◽  
Differential Difference Amplifier ◽  
Unity Gain ◽  
Folded Cascode ◽  
Speed And Accuracy

A high-speed and high-accuracy continuous-time common-mode feedback block (CMFB) is presented. To satisfy speed and accuracy requirements, some modifications have been applied on differential difference amplifier (DDA) CMFB circuit. The proposed method is applied to a folded cascode op-amp with power supply of 3.3 V. In order to verify the proposed circuit, simulations are done in 0.35 μm standard CMOS technology. In the worst condition when the output common-mode (CM) voltage is initialized to VCC or GND, only 1.1 ns is required to set the output CM voltage on the desired level. Also in a wide range of input CM voltage variations, the deviation of the output CM voltage from reference voltage is less than 6 mV, so simulation results confirm the expected accuracy and speed while simultaneously the proposed CMFB circuit preserves other characteristics of DDA CMFB circuit such as unity gain frequency, 3-dB bandwidth, phase margin and linearity.

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