US 6,661,301 B2 · Oscillator circuit

Abstract

An oscillator circuit with connectable capacitance makes it possible for the oscillator to change over between at least two frequencies. A switching unit is provided for the changeover. The switching unit has a first switch which is connected between the switchable capacitances, and also further switches, which are connected with respect to a supply voltage terminal. Compared with conventional oscillators that can be changed over, the novel circuit provides for the advantage that a particularly low forward resistance takes effect in the switched-on state of the connectable capacitances and particularly small parasitic capacitances nevertheless take effect in the switched-off state. The oscillator circuit can be implemented with a particularly small chip area since the switches can be integrated in a common transistor structure with a common control terminal. The oscillator circuit is particularly suitable for mobile radio applications.

Claims11

Dependent claims

An oscillator circuit, comprising:

a symmetrically constructed oscillator core with a least one inductance and at least one capacitance forming a resonant circuit with a symmetrical oscillation node;
two switchable capacitances connected via a respective terminal to said oscillation node and forming a switching node at free terminals thereof;
and
a switching unit connected to said switchable capacitances for altering a resonant circuit frequency by activating said switchable capacitances, said switching unit including a first switch for a direct low-impedance connection to one another of said free terminals of said switchable capacitances and further switches for a low-impedance connection of said free terminals of said switchable capacitances to a supply voltage, said first switch and said further switches being MOS transistors and being integrated in a common transistor structure of said switching unit, a source region of one of said further switches also forming a drain region of said first switch, and a drain region of another of said further switches also forming a source region of said first switch.

1 more element

Dependencies are inferred from the claim text.

Oscillator circuit

Life of this patent

Oscillator circuit

Life of this patent

Abstract

Claims11