A temperature responsive transmitter is provided in which frequency varies linearly with temperature. The transmitter includes two identically biased transistors connected in parallel. A capacitor, which reflects into the common bases to generate negative resistance effectively in parallel with the capacitor, is connected to the common emitters. A crystal is effectively in parallel with the capacitor and the negative resistance. Oscillations occur if the magnitude of the absolute value of the negative resistance is less than the positive resistive impedance of the capacitor and the inductance of the crystal. The crystal has a large linear temperature coefficient and a resonant frequency which is substantially less than the gain-bandwidth product of the transistors to ensure that the crystal primarily determines the frequency of oscillation. A high-Q tank circuit having an inductor and a capacitor is connected to the common collectors to increase the collector current flow which in turn enhances the radiation of the oscillator frequency by the inductor.

/pdf/temperature-responsive-transmitter-194v25x75t.pdf

Temperature responsive transmitter

A regulator circuit to control the output of a charge pump circuit, to reduce the effects of operating temperature and process variations on available output current from the charge pump circuit. A predetermined fraction of the output voltage of the charge pump circuit is fed back to the input of a differential amplifier, which compares it to a reference voltage. The output of the differential amplifier feeds a voltage controlled oscillator (VCO), which in turn generates a clock signal that is used to drive the charge pump circuit. The normal temperature characteristics of this configuration cause the output of the charge pump circuit to degrade with temperature changes. The regulator circuit can be placed between the differential amplifier and the VCO to adjust the volate driving the VCO comprising a biasing resistor with a negative temperature coefficient or multiple such resistor selectable with programmable logic.

Degenerative load temperature correction for charge pumps

In a light-emitting-diode lamp, there is provided an input impedance-changing circuit for establishing a low input impedance circuit when the light-emitting-diode lamp is missingline turned off. This input impedance-changing circuiting comprises Shunt circuit section, and a detector circuit section. The shunt circuit section includes a low impedance element and a controllable switching device connected in series. The detector circuit section detects turning off of the light-emitting-diode lamp and, in response to such detection, close the switching device to thereby cause electric current to flow through the shunt circuit section in order to simulate lower input impedance of the light-emitting-diode lamp. When the light-emitting-diode lamp replaces a conventional traffic signal incandescent lamp, the input impedance-changing circuitry prevents the conflict monitor of the already installed traffic-light lamp system to detect a high lamp impedance and accordingly a faulty lamp.

LED lamp with a fault-indicating impedance-changing circuit

A voltage-controlled oscillator includes a compensating signal value calculator which calculates the value of a function representing the portion of the oscillator temperature-frequency transfer curve corresponding to the ambient temperature. A signal corresponding to the calculated value is then applied to the voltage-contrtolled oscillator as the control voltage. Basically, an oscillator temperature-frequency transfer curve is partitioned into n segments. For each segment an offset value, xn, equal to the difference between the frequency at the start of the segment and the desired frequency, is stored in a look-up table. When a compensating signal value is required, the compensating signal value calculator retrieves from the look-up table the xn values corresponding to the segment containing the ambient temperature, segment ''k'', and the segments immediately preceding and succeeding segment k, segments ''k-1'' and ''k+1''. The retrieved values are labeled xk, xk-1, and xk+1, respectively. It then calculates a function representing the portion of the transfer curve passing through three points corresponding to the values (2). The compensating signal value is then calculated by substituting the actual delta T value into the equation. If the oscillator output frequency has shifted due to aging of the crystal, an aging offset value, xA, is added to the equation, and the compensating signal compensates for frequency variations related to both temperature and aging.

Oscillator temperature compensating circuit using stored and calculated values

A temperature compensated crystal oscillator including: an oscillation circuit having a quartz crystal resonator and a control terminal, for providing an oscillating signal determined by the quartz crystal resonator and a control signal, the control signal being applied to the control terminal; a temperature detecting circuit for detecting an operation temperature and outputting a temperature signal based on the operation temperature; and a control signal generating circuit for receiving the temperature signal from the temperature detecting circuit, generating the control signal based on a characteristic curve, and outputting the control signal to the control terminal; the characteristic curve essentially consisting of a plurality of straight lines and being an approximation of an ideal control curve in a predetermined operation temperature range including the operation temperature, the ideal control curve having a relationship between the control signal and the temperature signal for ideally compensating a fluctuation of a frequency of the oscillating signal against changes of the operation temperature, the predetermined operation temperature range being divided into temperature ranges, each of the plurality of straight lines corresponding to one of the divided temperature ranges.

Temperature compensated crystal oscillator

A temperature compensated crystal oscillator in which the base emitter voltage of transistors in an integrated circuit is used to provide substantially linearly temperature sensitive outputs which are employed to generate a series of polynomial functions of Chebyshev-like form which are summed and used to control a varicap diode in the oscillator feedback path.

James Stanley Wilson

Papers

Temperature controlled crystal oscillator arrangement

Temperature controlled crystal oscillator