Search

Viewing the input capacitance of a mosfet amplifier stage as an integral part of a microstrip transmission line, leads to a distributed amplifier of simple design. With today's mosfets, a bandwidth in excess of 500 MHz can be achieved; it will be possible to extend this bandwidth substantially in the future by the use of mosfets with lower input capacitance. In addition, some data are given on transmission lines employing substrates of high dielectric permittivity. [ABSTRACT FROM AUTHOR]

It is shown that, when biased for minimum source-gate voltage temperature variation, a source-follower using an enhancement mode MOSFET (Metal Oxide Silicon Field Effect Transistor) and a resistive load has a small signal low frequency voltage gain, A, which may be significantly less than unity. Typically, A < 0.94; optimized performance comes from operating at constant drain current, in which case A > 0.98 can be realized.
The inherently high input impedance characteristic of the Metal Oxide Silicon Field Effect Transistor (MOSFET) is exploited in the design of such analogue-type circuits as buffer amplifiers and sample-and-hold schemes. The simplest MOSFET buffer amplifier uses the device in the common drain or ' source-follower' configuration. In this arrangement it is preferable to choose the d.c. operating conditions so that the MOSFET is biased for minimum source-gate temperature variation. This ensures that the output (source) voltage temperature variations are minimised.
Often a simple resistive load is used to achieve the required biasing condition. For this situation, it is shown below that a voltage gain which may be unacceptably low for a ' unity-gain ' circuit is obtained. [ABSTRACT FROM AUTHOR]

A two-dimensional analysis of gallium arsenide and silicon junction FETs with the same geometries and impurity concentrations is presented. A field dependent mobility is used. The voltage-current characteristics are found to be different, while the charge distributions and electric fields in the channel are very similar. The importance of the field dependent mobility on the charge distribution is discussed. [ABSTRACT FROM AUTHOR]

The ideal modulation characteristic of a symmetrical JFETT is discussed and compared with the characteristic of an asymmetrical device. A new result has been obtained by the application of a positive bias on one of the gates of the asymmetrical device; this enables its modulation characteristic to approximate closely to the ideal linear modulation characteristic.
This paper deals, briefly, in its first part with the modulation characteristic of a symmetrical JFETT. The second part deals with the asymmetrical JFETT and compares its modulation characteristic with that of a symmetrical device. It describes further a new method of correcting the modulation characteristic of an asymmetrical device using a positive bias on one of the gates. By this method one can extend the linear range of the modulation characteristic of an asymmetrical JFETT and approach closely to the ideal modulation characteristic of a symmetrical device. [ABSTRACT FROM AUTHOR]

This paper treats a transmission-line model of the insulated-gate field-effect transistor (also known as the metal-oxide-semiconductor or MOS transistor) in the pre-pinchoff mode in order to determine the small-signal response of the device. The results are presented in terms of the canonical set of four complex admittance parameters which are dependent on frequency, the bias conditions, and known, constants of the device. It develops that the transmission line involved is a non-uniform one composed of non-linear elements leading to differential equations of some complexity. These are solved by each of two methods (one an infinite-series technique, the other an analogue simulation) and the results compared. Finally, the behaviour of the device connected as a simple amplifier in the common-source configuration is investigated. [ABSTRACT FROM AUTHOR]

This communication discusses the use of F.E.T. input stages in high impedance unit gain amplifiers. The circuits rely mainly on the use of matched transistors to achieve temperature and d.c. off-set compensation.
It is well known that the voltage controlled nature of an F.E.T. makes it ideal for use in high input impedance amplifiers: however, non-linear gain, d.c. off-set and temperature dependence are properties not so desirable; this paper presents methods of overcoming or compensating the latter whilst retaining the former.
Several circuits are given, each employing an F.E.T. input stage: each has its own advantages, but all have an input impedance greater than 100 M and a nominal gain of + 1. [ABSTRACT FROM AUTHOR]