Amplifiers – Signal feedback – Combined with control of bias voltage of signal amplifier
Patent
1975-01-10
1976-08-31
Rolinec, R. V.
Amplifiers
Signal feedback
Combined with control of bias voltage of signal amplifier
330 30D, 357 28, H03F 132
Patent
active
039784185
ABSTRACT:
A low frequency electro-thermal filter includes a pair of thermally coupled transistorized differential amplifiers. One of the differential amplifiers comprises a pair of heater transistors and the other differential amplifier includes a pair of sensor transistors, each heater transistor and its associated sensor transistor being fabricated on a single semiconductor chip. The heater transistors in the first differential amplifier serve differentially to heat the sensor transistors in the second differential amplifier in response to an input signal. The differential heating of the second differential amplifier differentially affects the electrical parameters of the sensor transistors and tends to upset the current balance between the stages of the second differential amplifier. A feedback loop is provided around the second differential amplifier for reestablishing the current balance thereof. The feedback signal has a rate of response that is dependent on the thermal response of the thermal coupling between the two differential amplifiers, and may be monitored to provide a filtered output signal.
The characteristics of the filter are determined by the thermal characteristics of the thermal coupling and by the electrical characteristics of the second differential amplifier and the feedback loop. The thermal characteristics of the thermal coupling are determined by the size, shape, thermal conductivity and thermal capacity of the semi-conductor chip forming the heater and sensor transistors and its associated substrate. The size, shape and placement of the heater and sensor transistors may be adjusted to select whether the thermal characteristics of the chip or the insulator primarily determine the thermal transfer function.
REFERENCES:
patent: 3321716 (1967-05-01), Lyon-Caen
patent: 3383614 (1968-05-01), Emmons et al.
patent: 3445777 (1969-05-01), Amodei
Dahl Lawrence J.
Rolinec R. V.
University Patents Inc.
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