Publications (17)6.95 Total impact
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ABSTRACT: A new measurement setup is presented that allows the observation of 1/f noise spectra in MOSFET's under switched bias conditions in a wide frequency band (10 Hz100 kHz). When switching between inversion and accumulation, MOSFET's of different manufacturers invariably show reduced 1/f noise power density for frequencies below the switching frequency. At low frequencies (10 Hz), a 58 dB reduction in intrinsic 1/f noise power density is found for different devices, largely independent of the switching frequency (up to 1 MHz). The switched bias measurements render detailed wideband 1/f noise spectra of switched MOSFET's, which is useful for 1/f noise model validation and analog circuit design.  [Show abstract] [Hide abstract]
ABSTRACT: A twostage lowvoltage CMOS op amp with railtorail input and output voltage ranges is presented. The circuit uses complementary differential input pairs to achieve the railtorail commonmode input voltage range. The differential pairs operate in strong inversion, and the constant transconductance is obtained by keeping the sum of the square roots of the tail currents constant. Such an input stage has an offset voltage which depends on the common input voltage level, resulting in a poor commonmode rejection ratio. Therefore, special attention has been given to the reduction of the op amp’s systematic offset voltage. Gainboost amplifiers are connected in a special way to provide not only an increase of the lowfrequency openloop gain, but also to provide a significant reduction of the systematic offset voltage. 
Conference Paper: A 16bit D/A interface with sinc approximated semidigital reconstruction filter and reduced number of coefficients
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ABSTRACT: Due to components nonidealities, the analog reconstruction is the most difficult analog building block in a D/A converter. The paper presents a 16bit D/A interface with a current driven semidigital filter and reduced number of coefficients. To optimise the number of coefficients an iterative method based on Sinc approximation has been used. With only 25 coefficients we get more than 50dB stopband rejection of noise. A differential solution is proposed to reduce the digital crosstalk and to increase the output swing. The D/A interface has been realised on chip in a 0.8µm CMOS 5V technology. S/N+THD measurements are provided.  [Show abstract] [Hide abstract]
ABSTRACT: In mixed level applications, accurate voltage references are difficult to realise due to the lack of lateral pnps and the large offsets inherent to CMOS opamps. If low power is essential, the accuracy is mainly impaired by the increased offset of the opamps. It is shown that by using chopping techniques, the accuracy of a bandgap voltage reference can be improved by about ten times without laser trimming, with the added benefit of reducing the 1/f noise of the amplifier  [Show abstract] [Hide abstract]
ABSTRACT: The authors investigate the realisation of a low voltage, large swing tunable transconductor in a 0.5 μm CMOS technology which preserves a constant input window for all tuning conditions. To preserve the DR at low voltages, large swings are required. This conflicts with the voltage limitation imposed by the power supply and distortion figures. This structure overcomes the problems related to nonidealities of the modern MOS transistor in terms of tunability range and linearity. The transconductance can be digitally tuned, in 10 coarse steps, and continuously tuned between coarse steps in the range 3085 μA/V. The large swing properly yields a large dynamic range over power ratio  [Show abstract] [Hide abstract]
ABSTRACT: This paper describes the principle and the design of a CMOS low noise, low residual offset, chopped amplifier with a class AB output stage for noise and offset reduction in mixed analog digital applications. The operation is based on chopping and dynamic element matching to reduce noise and offset, without excessive increase of the charge injection residual offset. The main goal is to achieve low residual offsets by chopping at high frequencies reducing at the same time the 1/f noise of the amplifier. Measurements on a 0.8 μm CMOS realization show reduction of 1/f noise and 18nV/√Hz residual thermal noise at low frequencies. The residual offset is lower than 100 μV up to 8 MHz chopping frequency. Driving a 32 Ω load the linearity is better than 80 dB and better than 88 dB for a 1 kΩ load at 1 kHz  [Show abstract] [Hide abstract]
ABSTRACT: In this paper an eightorder continuoustime Butterworth bandpass filter with quality factor of 10 is presented, intended to be used for selectivity in modern DECT handset receivers. A distortion analysis is performed and a model to describe the frequency dependent SpuriousFree DynamicRange (SFDR) in absolute value is presented. Measurements show a SFDR of 48 dB with a 3 mW power consumption. I. Introduction Until now, SurfaceAcousticWave (SAW) filters are frequently used in DECT handset receivers for selectivity. However, they have some disadvantages: the relatively large package, the fixed inputoutput impedance, the insertion loss and the high cost. The aim of the filter to be presented is to beat these disadvantages by integrating selectivity along with other radio circuits. These radio circuits are already realized in a highfrequency bipolar process, and therefore, the integrated filter must be bipolar too. Digital filters require A/Dconverters with a considerable power con...  [Show abstract] [Hide abstract]
ABSTRACT: This paper describes the principle and the design of a 0.5¯m CMOS, lowpower, lowvoltage, chopped amplifier for noise and offset reduction in mixed analogue digital applications. The operation is based on chopping and dynamic element matching to reduce noise and offset, without excessive increase of the charge injection residual offset. It consists of a chopped transconductance stage and a new class AB stage capable of working at 1.3V supply voltage. The main goal is to achieve low residual offsets by chopping at high frequencies reducing at the same time the 1/f noise of the amplifier. Loaded with a heavy load 32Omega jj 300pF it has a 91dB open loop gain and a GBW of 1.8MHz. Simulations show a THD of90dB for a 1kOmega load and83dB for a 32Omega load and 1KHz input signal. The simulated static offset is 1.67mV. The simulated residual offset is 450¯V at 10MHz chopping. At 1KHz chopping, the offset becomes lower than 1¯V. I. Introduction In a CMOS technology for mixed signal appl... 
Conference Paper: Realization of a 10 MHz integrated bipolar DECT bandpass filter
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ABSTRACT: In this paper an eightorder continuoustime Butterworth bandpass filter with quality factor of 10 is presented, intended to be used for selectivity in modern DECT handset receivers. A distortion analysis is performed and a model to describe the frequency dependent SpuriousFree DynamicRange (SFDR) in absolute value is presented. Measurements show a SFDR of 48 dB with a 3 mW power consumption.  [Show abstract] [Hide abstract]
ABSTRACT: A low voltage CMOS op amp is presented. The circuit uses complementary input pairs to achieve a railtorail common mode input voltage range. Special attention has been given to the reduction of the op amp's systematic offset voltage. Gain boost amplifiers are connected in a special way to provide not only an increase of the lowfrequency openloop gain but also a significant reduction of the systematic offset voltage 
Conference Paper: A CMOS railtorail linear VIconverter
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ABSTRACT: A linear CMOS VIconverter operating in strong inversion with a commonmode input range from the negative to the positive supply rail is presented. The circuit consists of three linear VIconverters based on the difference of squares principle. Two of these perform the actual V to I conversion, while the third changes the bias currents of the first two in response to changes in the input commonmode level. The resulting circuit has a large signal transconductance which is constant to within 3% over the entire commonmode input range. It can operate from a single supply voltage of 2.2 volts 
Article: Railtorail constantgm input stage and class AB output stage for lowvoltage CMOS op amps
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ABSTRACT: In this paper an input stage and an output stage are presented for application in lowvoltage CMOS operational amplifiers. The input stage operates in strong inversion and has a railtorail commonmode input voltage range. The transconductance (g m ) is insensitive to the commonmode input voltage. The class AB output stage has a railtorail output range. A class AB control circuit prevents any transistors in the output stage from switching off. This improves the largesignal highfrequency behavior and the step response of the amplifier. A complete twostage Op Amp employing the proposed input and output stages was realized in a semicustom CMOS process with minimum channel lengths of 10m and transistor threshold voltages of approximately 0.7 V. The measured minimum supply voltage is 2.5 V. The measured input voltage range exceeds the supply rails and the output voltage reaches both rails within 130 mV. The unitygain bandwidth of the complete Op Amp is severely limited by the long channel lengths. Simulations show that a unitygain bandwidth of 7 MHz is feasible if 2.5m channel lengths are used.  [Show abstract] [Hide abstract]
ABSTRACT: Two 3.3V operational amplifiers with constantg m railtorail input stage and railtorail output stage are presented. The constant transconductance (g m ) ensures a constant unitygain frequency within the whole commonmode input range. Two new methods to control theg m are introduced. Both operational amplifiers use the same railtorail output stage. The operational amplifiers have been integrated in a CMOS semicustom process with transistor lengths of 10m. The commonmode input voltage swing extends beyond the positive supply rail by 400 mV and beyond the negative supply rail by 200 mV. The output voltage is able to reach within 130 mV of the supply rails. The output current of the operational amplifiers is 2 mA and the voltage gain is 85 dB. The unitygain frquency is 165 kHz, which is mainly limited by the relatively long transistor lengths of 10m. In another process with channel lengths of 2m, simulation results showed that a unitygain frequency of 4 MHz can easily be obtained. 
Article: Simple railtorail lowvoltage constanttransconductance CMOS input stage in weak inversion
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ABSTRACT: A CMOS input stage for operational amplifiers is presented. To obtain a railtorail input range an nMOS and a pMOS differential pair are driven in parallel. Both differential pairs operate in weak inversion. With the help of only four additional transistors a transconductance g<sub>m</sub> is obtained which is independent of the common input voltage. This extension does not increase the minimum required supply voltage. 
Conference Paper: A lowvoltage CMOS op amp with a railtorail constantgm input stage and a class AB railtorail output stage
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ABSTRACT: A lowvoltage twostage operational amplifier (opamp) is presented. The opamp features railtorail operation and has an input stage with a constant transconductance (g<sub>m</sub>) over the entire commonmode input range. The input stage consists of an n and a pMOS differential pair connected in parallel. The constant g<sub>m</sub> is accomplished by regulating the tailcurrents with the aid of an MOS translinear (MTL) circuit. The resulting g<sub>m</sub> is constant within 5%. The commonsource output stage employs a feedback circuit which also contains an MTL circuit. This feedback circuit ensures class AB operation and prevents the transistors in the output stage from cutting off. The opamp isi realized in a semicustom CMOS process with minimum channel lengths of 10μm. Simulations show that the minimum supply voltage is less than 2.5 V. A unity gain bandwidth of 550 kHz and a DC voltage gain larger than 80 dB are feasible. The input range exceeds the supply rails, whereas the output range reaches the rails within 130 mV  [Show abstract] [Hide abstract]
ABSTRACT: Two 3V CMOS lowvoltage operational amplifiers (opamps) with constant transconductance ( g <sub>m</sub>) railtorail input stages are presented. The constant g <sub>m</sub> ensures a constant unitygain frequency within the whole commonmode input range. Two new methods to control the g <sub>m</sub> of the input stage are introduced. The opamps contain the same classAB output stage with railtorail output swing. The commonmode input voltage swing extends the positive supply rail by 600 mV and the negative supply rail by 200 mV. The output voltage can reach the supply rails within 130 mV. The output current of the opamps was limited to ±2 mA, voltage gain was 85 dB, and the unitygain frequency was 165 kHz. The opamps were integrated in a semicustom CMOS process with transistor lengths of 10 μm  [Show abstract] [Hide abstract]
ABSTRACT: This paper describes the principle and the design of a CMOS low, noise, low, residual offset, chopeed, amplifier with a class AB output stage for noise and, offset reduction in mixed analog digital, applications.. The operation is based on chopping. and dynamic element matching to reduce noise and offset,2 withput excessive increase of: the charge injFction residual, offset. The main goal is to, achieve low residual offsets by chopping at high, frequencies reducing at the same time the l/f noise ofi the amplifier. Measurements on a 0.8pm CMOS realization, show reduction of l/f noise and 18nVIdHz residual thermal npise at low fqequencies, The residual offset is losyer than 100kV up>to 8MHz chopping frequency. Driving, a 329, load the linearity is better than 8OdB and better.than 88dB,for a lkQ,load,at 1KHz.
Publication Stats
312  Citations  
6.95  Total Impact Points  
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Institutions

19952000

University of Twente
 • IC Design Group
 • Department of Electrical Engineering
Enschede, Overijssel, Netherlands
