A CIRCUIT AND NOISE MODEL FIELD-EFFECT TRANSISTOR
Abstract
The field-effect transistor is treated from an active R-C transmission-line approach, and a circuit model is derived from a lumped-element approximation to the line. The circuit model is found to be similar to that often stated for the high-frequency (hf) circuit model of the vacuum tube. The model is characterized by the low frequency (1-f) admittance parameters and two high-frequency parameters: the cutoff frequency (which is the frequency at which the hf transconductance falls to one-half of its 1-f value) and a constant relating to the input conductance. A maximum, useful frequency for the device, which is close to the cutoff frequency, is calculated from the model. Measurements are found to be in agreement with the predictions of the theory for frequencies less than the cutoff frequency. A noise model for the field-effect transistor is derived by assigning thermal-noise generators to the conductive elements of the transmission line model and shot-noise generators to the gate junction. The input-noise current is then found to be proportional to the input conductance and leakage current, and the output-noise current is proportional to the output conductance, transconductance, and leakage current. This model is shown by experiment to be valid for frequencies where 1/f noise is not important.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 1963
- Accession Number
- AD0407177
Entities
People
- N. G. Bechtel Jr.
Organizations
- Stanford University