Apparatus and methods for variable capacitor arrays
Apparatus and methods for variable capacitor arrays are provided herein. In certain configurations, an apparatus includes a variable capacitor array and a bias voltage generation circuit. The variable capacitor array includes a plurality of metal oxide semiconductor (MOS) variable capacitor cells, which include one or more pairs of MOS capacitors implemented in anti-parallel and/or anti-series configurations. In certain implementations, the MOS variable capacitor cells are electrically connected in parallel with one another between a radio frequency (RF) input and an RF output of the variable capacitor array. The bias voltage generation circuit generates bias voltages for biasing the MOS capacitors of the MOS variable capacitor cells.
1. An apparatus comprising:
a radio frequency (RF) signal processing circuit comprising a plurality of variable capacitor arrays including a first variable capacitor array, wherein the first variable capacitor array comprises:
a first plurality of metal oxide semiconductor (MOS) variable capacitor cells, wherein the first plurality of MOS variable capacitor cells comprises a first MOS variable capacitor cell comprising a first MOS capacitor and a second MOS capacitor, wherein the first MOS capacitor and the second MOS capacitor are arranged in an anti-series configuration or in an anti-parallel configuration;
a bias voltage generation circuit configured to bias the first plurality of MOS variable capacitor cells to control a capacitance of the first variable capacitor array; and
a capacitance correction circuit configured to generate an adjusted control signal based on a control signal and a band signal, wherein the bias voltage generation circuit is configured to receive the adjusted control signal.
2. The apparatus of claim 1 , wherein the first MOS capacitor includes a source and a drain electrically connected to one another to operate as a cathode, wherein the first MOS capacitor further comprises a gate configured to operate as an anode, wherein the bias voltage generation circuit is configured to bias the first MOS capacitor with a first bias voltage applied between the anode and the cathode of the first MOS capacitor, wherein the bias voltage generation circuit is configured to control the first bias voltage to a voltage level selected from a discrete number of two or more bias voltage levels.
3. The apparatus of claim 2 , wherein the bias voltage generation circuit is configured to control the first bias voltage to either a first bias voltage level or to a second bias voltage level.
4. The apparatus of claim 3 , wherein the first bias voltage level is configured to operate the first MOS capacitor in an accumulation mode, wherein the second bias voltage level is configured to operate the first MOS capacitor in an inversion mode.
5. The apparatus of claim 2 , wherein the bias voltage generation circuit is configured to receive a digital control signal configured to control selection of the voltage level from the two or more bias voltage levels.
6. The integrated circuit of claim 1 ,
wherein the first MOS capacitor comprises a source and a drain electrically connected to one another to operate as a cathode, wherein the first MOS capacitor further comprises a gate configured to operate as an anode, and
wherein the second MOS capacitor comprises a source and a drain electrically connected to one another to operate as a cathode, wherein the second MOS capacitor further comprises a gate configured to operate as an anode.
7. The apparatus of claim 6 , wherein the anode of the first MOS capacitor is electrically connected to the anode of the second MOS capacitor.
8. The apparatus of claim 6 ,
wherein the cathode of the first MOS capacitor is electrically connected to the cathode of the second MOS capacitor.
9. The apparatus of claim 8 , wherein the first MOS variable capacitor cell of the first plurality of MOS variable capacitor cells further comprises a third MOS capacitor and a fourth MOS capacitor,
wherein an anode of the third MOS capacitor is electrically connected to an anode of the fourth MOS capacitor, wherein a cathode of the third MOS capacitor is electrically connected to the anode of the first MOS capacitor, and wherein a cathode of the fourth MOS capacitor is electrically connected to the anode of the second MOS capacitor.
10. The apparatus of claim 1 , wherein the integrated circuit does not include any switches along a signal path between the first RF input and the first RF output through the first variable capacitor array.
11. The apparatus of claim 1 , wherein the first plurality of MOS variable capacitor cells comprises between about 6 and about 12 cells.
12. The apparatus of claim 11 , wherein the first plurality of MOS variable capacitor cells are scaled in size relative to one another.
13. The apparatus of claim 12 , wherein the scale factor is equal to about 2.
14. The apparatus of claim 1 , further comprising a balancing resistor electrically connected in parallel with the first MOS variable capacitor cell of the first plurality of MOS variable capacitor cells.