The research described in this thesis is concerned with analysis and design of "HighTransconductance
RF MOSFET Voltage-to-Current (V-I) Converters". Various V-I
converter circuits published in the past have been reviewed by the author in order to
understand the different techniques employed to improve transconductance (Gt),
linear operating range and total harmonic distortion (THO). Throughout this research,
the emphasis has been to improve the above mentioned parameters. All the V-I
converter circuits reported have been simulated using PSPICE and the results
compared with the values obtained by theoretical analysis. Some of the results of this
work have been already reported by the author in the technical literature. (See
Chapter 9, at the end of this thesis, where reference to two publications by the author
is given.)
It was essential to obtain accurate CMOS device parameters values, such as Early
Voltage, transconductance parameter ratios!! (gm/gds), X (gmbl'gm) and inter-electrode
capacitances, to facilitate the design the prQcess. This was achieved using an
extensive set of simulations for the transistor operating under different bias
conditions. Furthermore, a measurement technique, thought to be novel, for the direct
determination of the transconductance ratios!! and X is proposed.
In the next part of the work several types of current mirror are compared against the
standard current mirrors, using analytical and simulation methods. Furthermore
several MOSFET V-I converter designs were critically reviewed to understand the
various existing techniques and their limitations.
Two novel techniques, Drain-Source Feedback Circuits (DSFCs) and Drain-Gate
Feedback Circuits (OGFCs) ere implemented with a new temperature-compensation
scheme, designed to operate well in an industrial environment (-40°C - +8S°C). It is
found that the best types of V -I converters were the DSFCs which, offer a more
accurate value of Gt (3.386mS) and the THO less than -S7dB for a differential input
operating range SOOm V at 1 GHz with a 3V total rail voltage. The OGFC circuits
were also meet the initial design targets, the value of THO is less then -SOdB, and
operating in the Giga hertz frequency range is possible. Preliminary investigation on
future work shows promising results