The Flipped Voltage Follower: Theory and Applications

Ramírez-Angulo, J.; Valero-Bernal, Maria Rodanas; López-Martín, Antonio J.; Carvajal, R.G.; Torralba, A.; Celma-Pueyo, S.; Marques, Nicolas

doi:10.1007/978-3-642-36329-0_12

Cited by 11 publications

(12 citation statements)

References 19 publications

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“…2. It has a class-AB input stage [12] implemented with Cascoded Flipped Voltage Followers (CFVFs shown in blue color) [13] with an adaptive biased load (Mp, Mcp) [6] and an adaptive biased tail transistor (Mnt', Mcnt). The class-AB differential pair generates transient currents i 1 , i 2 with peak values much higher than I bias .…”

Section: Proposed Schemementioning

confidence: 99%

High current efficiency class-AB OTA with high open loop gain and enhanced bandwidth

Pourashraf

Ramírez-Angulo

Roman‐Loera

et al. 2017

IEICE Electron. Express

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An efficient class-AB OTA with enhanced output current, slew rate, open loop gain, and gain bandwidth is presented. The circuit is based on a class-AB input stage with adaptive biasing, and an output stage with dynamically biased cascode transistors. It can deliver output currents 100 times larger than the bias current with a total quiescent power dissipation of 72 µW. Measurement results of a 180 nm CMOS test chip prototype show slew rate, gain bandwidth, and open loop gain enhancement.

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Section: Proposed Schemementioning

confidence: 99%

High current efficiency class-AB OTA with high open loop gain and enhanced bandwidth

Pourashraf

Ramírez-Angulo

Roman‐Loera

et al. 2017

IEICE Electron. Express

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“…It has a class AB differential pair with input transistors M 1A and M 2A which are class AB biased using cross-coupled floating batteries [4], [7]. Note that the SC can be implemented in different ways, like the circuit published in [8] based on the class AB differential amplifier reported in [9].…”

Section: Auxiliar Squaring Circuit For Opamps' Tailmentioning

confidence: 99%

“…Down to their simplicity, low output resistance, high current sinking capability and low supply requirements, each level shifter has been implemented by using two wide input swing cascoded flipped voltage followers (CASFVFs) [11], as shown in Fig 3. They operate as high swing enhanced buffers with very low impedance nodes (R x = R y = 1/[g m (g m r o )] 2 ). Assuming both CASFVFs are matched, the input pair currents I 1 and I 2 are given by I 1 = 0.5·β·((2I B /β) 1/2 + V diff ) 2 (3a)…”

Section: B Current Boosting (V Diff ≠ 0)mentioning

confidence: 99%

“…The currents I 1 and I 2 are added, so the tail current I tail is I tail = I 1 + I 2 = 2·I B + β·|V diff | 2 (4) which is then proportional to the square value (magnitude) of the input differential voltage V diff .…”

Section: B Current Boosting (V Diff ≠ 0)mentioning

confidence: 99%

“…Here, the tail current of the OpAmp is controlled using an auxiliary circuit based on squaring circuits (SCs). The SCs use wide swing cascoded flipped voltage followers (FVFs) [4], [5] that enhance the maximum output currents (and slew rate) by a factor 10 to 15. These circuits increase the OpAmp's static power consumption by less than 20%.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Class AB two stage and folded cascode OpAmps based on a squaring circuit

Valero

Lopez-Martin

Thoutam

et al. 2015

2015 IEEE International Symposium on Circuits and Systems (ISCAS)

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This paper presents a novel adaptive bias technique based on the use of squaring circuits. Here, the tail current of an operational amplifier (OpAmp) is controlled using an auxiliary circuit. By design, it generates a well-controlled tail current which -to a first order approximation-is independent of the OpAmp's common-mode input voltage. As a result, parameters like common-mode rejection ratio (CMRR) and power supply rejection ratio (PSRR) are enhanced. However, when a differential input signal is applied, it generates a tail current proportional to the square of the OpAmp's differential input voltage. In this way, the currents of the OpAmp's input pairs are boosted, thus improving slew rate. Experimental results in 0.5 µm CMOS technology verify current and slew rate enhancement factors between 10 and 15 with less than 20% static current increase.

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Super class AB OTA without open‐loop gain degradation based on dynamic cascode biasing

Pourashraf

Ramírez-Angulo

López-Martín

et al. 2017

Circuit Theory & Apps

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A scheme to achieve simultaneously extremely high slew-rate improvement and avoiding open-loop gain degradation in one-stage super class AB op-amps is introduced. It overcomes the serious shortcoming of super class AB operational transconductance amplifiers that shows very high-output current enhancement factors at the expense of degrading the open-loop gain. The proposed scheme uses dynamically biased cascode transistors to avoid gain and slew-rate degradation. Experimental results of a super class AB operational transconductance amplifier in 180-nm complementary metal-oxide semiconductor technology with open-loop gain of 67 dB, a factor 2 improvement in GBW, and a current enhancement factor of 270 verify the proposed scheme.

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The Flipped Voltage Follower: Theory and Applications

Cited by 11 publications

References 19 publications

High current efficiency class-AB OTA with high open loop gain and enhanced bandwidth

High current efficiency class-AB OTA with high open loop gain and enhanced bandwidth

Class AB two stage and folded cascode OpAmps based on a squaring circuit

Super class AB OTA without open‐loop gain degradation based on dynamic cascode biasing

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