Current-controlled quadrature oscillator based on differential g.sub.m /C cells

An oscillator comprising:

• a first gm/C integrator stage having a first pair of input terminals, a first pair of output terminals, and a first pair of common-mode terminals;
• a first pair of common-mode transistors coupled between a supply voltage and the first pair of common-mode terminals, each one of the first pair of common mode transistors being coupled between the supply voltage and a respective one of the first pair of common-mode terminals, each one of the first pair of common mode transistors having a control terminal;
• a first common-mode biasing transistor having a control terminal coupled to a second gm/C integrator stage and a load terminal coupled to the control terminals of the first pair of common-mode transistors;
• a first start-up means coupled to the first pair of output terminals;
• the second gm/C integrator stage having a second pair of input terminals, a second pair of output terminals, and a second pair of common-mode terminals;
• a second pair of common-mode transistors coupled between the supply voltage and the second pair of common-mode terminals, each one of the second pair of common mode transistors being coupled between the supply voltage and a respective one of the second pair of common-mode terminals, each one of the second pair of common mode transistors having a control terminal;
• a second common-mode biasing transistor having a control terminal coupled to the first gm/C integrator stage and a load terminal coupled to the control terminals of the second pair of common-mode transistors;
• and
• a second start-up means coupled to the second pair of output terminals;
• wherein the first pair of output terminals is coupled to the second pair of input terminals and the second pair of output terminals is cross-coupled to the first pair of input terminals such that a signal appearing on the first pair of input terminals is 180 degrees out of phase with a concomitant signal appearing on the second pair of input terminals whereby the oscillator oscillates.

An oscillator comprising:

• a first gm/C integrator stage having a first pair of input terminals, a first pair of output terminals, and a first pair of common-mode terminals;
• a first common-mode biasing means coupled between a supply voltage and the first pair of common-mode terminals;
• a first pair of cross-coupled transistors coupled to the first pair of output terminals;
• a first biasing current source coupled to the first pair of cross-coupled transistors;
• a second gm/C integrator stage having a second pair of input terminals, a second pair of output terminals, and a second pair of common-mode terminals;
• a second common-mode biasing means coupled between a supply voltage and the second pair of common-mode terminals;
• and
• a second pair of cross-coupled transistors coupled to the second pair of output terminals;
• and
• a second biasing current source coupled to the second pair of cross-coupled transistors;
• wherein the first pair of output terminals is coupled to the second pair of input terminals and the second pair of output terminals is cross-coupled to the first pair of input terminals such that a signal appearing on the first pair of input terminals is 180 degrees out of phase with a concomitant signal appearing on the second pair of input terminals whereby the oscillator oscillates.

An oscillator comprising:

• a first gm/C integrator stage having a first pair of input terminals, a first pair of output terminals, and a first pair of common-mode terminals;
• a first common-mode biasing circuit coupled between a supply voltage and the first pair of common-mode terminals;
• a second gm/C integrator stage having a second pair of input terminals, a second pair of output terminals, and a second pair of common-mode terminals;
• a second common-mode biasing circuit coupled between a supply voltage and the second pair of common-mode terminals;
• and
• wherein the first pair of output terminals is coupled to the second pair of input terminals and the second pair of output terminals is cross-coupled to the first pair of input terminals such that a signal appearing on the first pair of input terminals is 180 degrees out of phase with a concomitant signal appearing on the second pair of input terminals whereby the oscillator oscillates.

A method of tuning an oscillation frequency of an oscillation signal generated by an oscillator having a pair of gm/C integrator stages, each gm/C stage having a tunable current source coupled thereto for sourcing current from the associated gm/C stage, the method comprising:

• cross-coupling the pair of gm/C stages to form a closed loop;
• applying a control signal to the oscillator;
• altering the currents through the gm/C stages responsive to the control signal;
• and
• altering the transconductance (grn) of the integrator stages responsive to the alteration in the currents wherein the oscillation frequency is tuned.