Adjustable frequency oscillator with regenerative feedback and a coupling unit including a differential amplifier for adjusting the feedback

Claim 2

An adjustable frequency oscillator comprising a negative feedback, operational amplifier functioning as an integrator whose output is connected to a bistable-bipolar threshold device, said threshold device comprising an operational amplifier connected as a Schmitt trigger and having a resistive negative feedback loop for providing a bistablebipolar output and switching the bipolar output from one stable state to the other stable state each time the input voltage applied thereto exceeds a predetermined fraction of the bipolar output and has a polarity opposite to the bipolar output, a regenerative feedback connection between the output of the threshold device and an input of the integrator and an adjustable coupling unit for adjusting the amount of regenerative feedback including a differential transformer having a primary winding feed from the output of said thershold device and a secondary winding connected to the input to said integrator, and a further operational amplifier connected to the output of said device having a negative feedback loop including a resistance and a capacitance connected in parallel, said further operational amplifier connecting said primary winding, to the output of said operational amplifier functioning as a Schmitt trigger.

Claim 3

An oscillator according to claim 1 wherein the time constant of the said negative feedback loop is substantially equal to the time consTant of the primary winding of the transformer.

Claim 4

An oscillator according to claim 2 wherein a damping resistor is connected across the secondary winding of the transformer.

Claim 5

An adjustable frequency oscillator comprising a negative feedback, operational amplifier functioning as an integrator whose output is connected to a bistable-bipolar threshold device, said threshold device comprising an operational amplifier connected as a Schmitt trigger and having a resistive negative feedback loop for providing a bistable-bipolar output and switching the bipolar output from one stable state to the other stable state each time the input voltage applied thereto exceeds a predetermined fraction of the bipolar output and has a polarity opposite to the bipolar output, an adjustable coupling unit, connected in a regenerative feedback loop between the output of the threshold device and an input of the integrator, for adjusting the amount of regenerative feedback and including a differential transformer for adjusting the amount of the regenerative feedback, the primary winding of which is fed from the threshold device and the secondary winding of which feeds the input of the integrator, said transformer having a primary winding feed from the output of said threshold device and a secondary winding feeding the input to said, integrator, the output of the said device being connected to the input of a further operational amplifier having a negative feedback loop including a resistance and a capacitance connected in parallel, said further operational amplifier connecting said primary winding to the output of said operational amplifier functioning as a Schmitt trigger.

Claim 6

An adjustable frequency oscillator comprising a negative feedback, operational amplifier functioning as an integrator whose output is connected to a bistable-bipolar threshold device, said threshold device comprising an operational amplifier connected as a Schmitt trigger and having a resistive negative feedback loop for providing a bistable-bipolar output and switching the bipolar output from one stable state to the other stable state each time the input voltage applied thereto exceeds a predetermined fraction of the bipolar output and has a polarity opposite to the bipolar output, an adjustable coupling unit, connected in a regenerative feedback loop between the output of the threshold device and an input of the integrator, for adjusting the amount of regenerative feedback and including a differential transformer for adjusting the amount of the regenerative feedback, the primary winding of which is fed from the threshold device and the secondary winding of which feeds the input of the integrator, said transformer having a primary winding feed from the output of said threshold device and a secondary winding feeding the input to said, integrator, the output of the said device being connected to the input of a further operational amplifier having a negative feedback loop including a resistance and a capacitance connected in parallel, said further operational amplifier connecting said primary winding to the output of said operational amplifier functioning as a Schmitt trigger.

Claim 7

An oscillator according to claim 4 wherein the time constant of the negative feedback loop is substantially equal to the time constant of the primary winding of the transformer.

Claim 8

An oscillator according to claim 4 wherein the transformer has a fixed coupling ratio, the primary winding of which is fed from the output of the threshold device and the secondary winding to which is connected to the input of a resistance bridge circuit which when balanced produces no regenerative feedback but when the balance is disturbed by a certain amount produces a corresponding amount of feedback, the output of the bridge circuit feeding the input of the integrator.

Claim 9

An oscillator according to claim 4 wherein a damping resistor is connected across the secondary winding of the transformer.