Temperature compensated field effect transistor crystal oscillator

Claim 2

A crystal-controlled oscillator circuit having an oscillaTor loop including a capacitance and a piezoelectric crystal to provide oscillating signals, and an output loop including means for applying signals to a signal line, wherein an improvement comprises: a junction field-effect transistor circuit having a source, a gate, and a drain, the drain being coupled to a bias voltage and to the applying means of the output loop, and the gate being coupled to the crystal in the oscillator loop; means, including a capacitance, for increasing the capacitance in the oscillator loop with decreasing operating temperatures of the oscillator circuit, the capacitance increasing means being coupled between the drain of the transistor circuit and the crystal to complete the oscillator loop from the drain of the transistor circuit through the crystal to the gate of the transistor circuit and through the transistor circuit to its drain; and means coupled between the source of the transistor circuit and ground return for the bias voltage, for increasingly limiting a current flow through the transistor circuit with decreasing operating temperatures of the oscillator circuit.

Claim 3

An improvement according to claim 1, wherein the current limiting means includes a resistive element which has a value of less than 20 ohms at a temperature of 60*C and of more than 700 ohms at a temperature of -40*C, and a by-pass capacitor in parallel with the resistive element for preventing signal voltage from becoming affected by the resistive element, the oscillator circuit further including a diode coupled in series to the by-pass capacitor and the resistive element of the current limiting means to prevent a conventional current flow into the source of the transistor circuit.

Claim 4

In an oscillator circuit having an oscillator loop including a piezoelectric crystal to generate oscillating signals, an output loop including means for inducing signals from the output loop in a signal line, and an active element for transferring the signals generated in the oscillator loop to the output loop, a temperature-compensated field-effect transistor device for replacing a vacuum tube as the active element in the oscillator circuit, which comprises: a field-effect transistor amplifier having a source, a gate and a drain corresponding to a cathode, a control grid and a plate of the tube, respectively, the gate being coupled to a first contact corresponding to a control grid termination of the tube, the first contact being coupled to a first terminal of the crystal, and the drain being coupled to a second contact corresponding to the plate of the tube, the second contact being coupled to a bias voltage and to the inducing means of the output loop; a first impedance, including a capacitance having a negative temperature coefficient, coupled to the drain of the amplifier and terminating in a third contact corresponding to a screen grid termination of the tube the third contact being coupled to a second side of the crystal; and a second impedance including a resistive element with a negative temperature coefficient coupled to the source of the amplifier and terminating in a fourth contact corresponding to the cathode termination of the tube, the fourth contact being coupled to a ground return for the bias voltage.

Claim 5

In an oscillator circuit having an oscillator loop including a piezoelectric crystal to generate oscillating signals, an output loop including means for inducing signals from the output loop in a signal line, and an active element for transferring the signals generated in the oscillator loop to the output loop, a temperature-compensated field-effect transistor device for replacing a vacuum tube as the active element in the oscillator circuit, which comprises: a field-effect transistor amplifier having a source, a gate and a drain corresponding to a cathode, a control grid and a plate of the tube, respectively, the gate being coupled to a first contact corresponding to a control grid termination of the tube, the first contact being coupled to a first terminal of the crystal, and the drain being coupled to a second contact corresponding to the plate of the tube, the second contact being coupled to a bias voltage and to the inducing means of the output loop; a first impedance, including a capacitance having a negative temperature coefficient, coupled to the drain of the amplifier and terminating in a third contact corresponding to a screen grid termination of the tube the third contact being coupled to a second side of the crystal; and a second impedance including a resistive element with a negative temperature coefficient coupled to the source of the amplifier and terminating in a fourth contact corresponding to the cathode termination of the tube, the fourth contact being coupled to a ground return for the bias voltage.

Claim 6

A crystal oscillator circuit having an oscillator loop, including a capacitance and a piezoelectric crystal to provide oscillating signals, an output loop including means for applying signals to a signal line, and an active element comprised of a junction field-effect transistor network having source, gate and drain terminals, the drain terminal being coupled to a bias voltage source, to a first terminal of the crystal, and to the applying means of the output loop, and the gate being coupled to a second terminal of the crystal in the oscillator loop, the circuit comprising: a capacitive impedance having a negative temperature coefficient inserted into the oscillator loop of the circuit, the capacitiVe temperature coefficient defining a change in capacitance of at least 1,000 parts per million per degree centigrade; an impedance comprising a capacitor in parallel to a resistor having a negative temperature coefficient, inserted into the output loop, the resistor having a value of less than 20 ohms at a temperature of 60* centigrade and of more than 700 ohms at a temperature of negative 40* centigrade; and a diode in the output loop of the circuit having an anode coupled to the source terminal of the network.

Claim 7

A crystal oscillator circuit having an oscillator loop, including a capacitance and a piezoelectric crystal to provide oscillating signals, an output loop including means for applying signals to a signal line, and an active element comprised of a junction field-effect transistor network having source, gate and drain terminals, the drain terminal being coupled to a bias voltage source, to a first terminal of the crystal, and to the applying means of the output loop, and the gate being coupled to a second terminal of the crystal in the oscillator loop, the circuit comprising: a capacitive impedance having a negative temperature coefficient inserted into the oscillator loop of the circuit, the capacitiVe temperature coefficient defining a change in capacitance of at least 1,000 parts per million per degree centigrade; an impedance comprising a capacitor in parallel to a resistor having a negative temperature coefficient, inserted into the output loop, the resistor having a value of less than 20 ohms at a temperature of 60* centigrade and of more than 700 ohms at a temperature of negative 40* centigrade; and a diode in the output loop of the circuit having an anode coupled to the source terminal of the network.