Alison Payne

Log-domain filtering and the Bernoulli cell

In this paper, the dynamic behavior of a nonlinear circuit element termed a Bernoulli cell is described, which is composed of a suitably biased bipolar junction transistor (BJT) and an emitter connected grounded capacitor. This cell has application in the synthesis of log-domain filters, since it facilitates the development of a low-level design approach in which a frequency-domain transfer function is decomposed into time-domain current product equalities that can be implemented by direct use of the translinear principle (TLP). Furthermore, the dynamic of a log-domain structure can be analyzed and its frequency response can be easily derived when the embedded Bernoulli cells are identified. An analysis and a synthesis example are presented.

A high Q RF CMOS differential active inductor

This paper presents the design of a differential CMOS active inductor for use in applications around 1-1.7 GHz. The architecture is based on a gyrator-C topology, where tuneable compensation techniques are applied to reduce phase error due to additional device parasitics, thus extending the useable frequency range of the inductor closer to the f/sub t/ of the technology. The inductance value and quality factor are also independently tuneable, and simulation results using device parameters from the AMS 0.8 /spl mu/m CMOS process demonstrate operation at 1.5 GHz with a Q of over 300. The implementation of a tuneable bandpass filter using the inductor is also demonstrated.

Log-domain filters, translinear circuits and the Bernoulli cell

In this paper a powerful analog circuit building block is identified, composed of a suitably biased npn bipolar junction transistor (BJT) with a grounded capacitor connected to the emitter. The collector current of the BJT is shown to have the form of Bernoullis general non-linear differential equation and this configuration is termed a Bernoulli cell. By means of a suitable change of variables, Bernoullis equation may be converted to a linear form and hence the Bernoulli cell can be exploited as a basic element for the synthesis of linear circuits.

State-space synthesis of biquads based on the MOSFET square law

This paper presents a design methodology for implementing integrators and biquads based on the square-law relationship between gate voltage and drain current in a saturated MOS transistor. The resulting circuit architecture is suitable for implementation in BiCMOS or CMOS VLSI technology.

Design of a low-voltage, low-power, wide-tuning integrated oscillator

This paper presents the design of a low-voltage, low-power, wide-tuning, monolithic voltage-controlled oscillator (VCO). The oscillator is based upon the classic LC-tuned negative-resistance topology, with a novel low-voltage, high performance active inductor. It operates in the 1.1 GHz to 2.1 GHz frequency range while consuming 1 mA from a 2.5 V power supply, with scope for further reduction to 1 V. The VCOs phase noise level is -83 dBc/Hz at 600 kHz offset from a 1.5 GHz carrier with a Q of 7 and can be further reduced to -88 dBc/Hz at 600 kHz offset from a 2.5 GHz carrier if the Q is increased to 24.

A 3-V RF CMOS bandpass amplifier using an active inductor

This paper presents the design of a 3-V RF CMOS bandpass amplifier using the recently proposed CMOS active inductor. Negative feedback is used with a cascode amplifier to realise a grounded inductance as a frequency selective element and achieve power amplification simultaneously. The proposed bandpass amplifier, which includes an input matching network and an output voltage buffer for a 50-/spl Omega/ environment, is designed and simulated with a commercial 0.8-/spl mu/m n-well BiCMOS process using HSPICE. Simulation results of the bandpass amplifier tuned at a centre frequency of 1 GHz with a quality factor of 56 illustrate that a power gain of 23 dB, and a noise figure of 4.3 dB can be achieved with a power dissipation of 57 mW from a single 3 V supply.

High frequency self-compensation of current-feedback devices

The authors examine the performance of a current-feedback operational amplifier configured as a closed-loop voltage amplifier in two extremes of operation, unity gain and high gain, and suggest methods to extend the frequency response of each by self-compensating these circuits. Mechanisms for high-frequency self-compensation are evident within the transfer function of the device. The authors exploit this feature to achieve high-gain and high-bandwidth structures. The compensation at high gains is achieved by reducing the input impedance of the op-amp, thus reducing high-gain bandwidth roll-off. The frequency performance of an op-amp configured as a unity gain buffer is significantly improved by taking the output from the input side of the device.<<ETX>>

Linear transfer function synthesis using non-linear IC components

This paper describes a methodology for the synthesis of linear transfer functions based on the use of non-linear components. Rather than using local linearisation techniques to eliminate the unwanted non-linearity, the non-linear characteristic of the component is directly incorporated into the state-space description of the network transfer function. Although this approach has been recently applied as the log-domain technique, in this paper the approach is generalised to include both CMOS and bipolar technologies.

A unified matrix method for systematic synthesis of log-domain ladder filters

This paper describes a matrix-based method of synthesizing log-domain ladder filters. The nodal matrix equations describing a LCR prototype are made directly realisable, facilitating the design of high order filters. The problem of floating capacitors normally required to realise transmission zeros in the log-domain is solved by matrix transformations. Simulated results of different designs derived by various matrix decompositions validate the proposed procedures, which have been formalised in the CAD filter package XFILTER.

Operational floating conveyor

A description is presented of the design of a versatile analog building block, termed an operational floating conveyor (OFC). The OFC has similar transmission properties to a current-feedback op amp, but with a differential current output which allows accurate output current sampling. This feature increases device versatility and enables accurate closed loop current amplifier topologies to be realized, including an accurate closed loop current conveyor. As a further development, the technique of active compensation is applied to the OFC to achieve very high performance current amplifier topologies.<<ETX>>