IMPROVEMENT OF LOW-TEMPERATURE FIELD-EFFECT TRANSISTORS.
Final technical rept. 22 Apr 66-22 Jan 67,
RADIO CORP OF AMERICA SOMERVILLE N J ELECTRONIC COMPONENTS AND DEVICES
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A low-temperature 4.2 K MOS amplifier was developed that exhibited a transconductance of 8 millimhos and an amplification factor of 400 at a power dissipation of 150 microwatts. The transconductance is close to the objective value of 10 millimhos, while the amplification factor far exceeds the objective of 10. Noise figures over the bandwidth from 3 hertz to 5 kilohertz, however, were far greater than the objective value of 2 db. The lowest noise figures obtained at liquid helium temperatures were about 40 db at 100 hertz and about 20 db at 5 kilohertz. A source resistance of 1G sub m was used in the calculations. The low-frequency spectral intensity of noise exhibited a 1f distribution, in agreement with theory. Noise figures at liquid helium temperatures were about 15 db, which was higher than expected. The equivalent input noise voltage was reduced by a factor of four in one case. It was determined that an inversion-layer channel exists at 4.2 K for effective gate voltages greater than zero. This layer, however, is strongly influenced by drain-to-channel feedback capacitance. When the effective voltage is less than zero, conduction is by space-charge-limited current. These factors explain the observed triode-like I-V characteristics rather than the normal pentode-like characteristics at liquid helium temperatures. The tetrode cascode of two triodes yields effective pentode characteristics that result in high amplification with equivalent triode noise. Author
- Electrical and Electronic Equipment
- Solid State Physics