Impedance control in radio-frequency switches
A radio-frequency switch includes a first field-effect transistor disposed between a first node and a second node, the first field-effect transistor having a source, a drain, a gate, and a body. The switch further includes a coupling path connected between the body of the first field-effect transistor and the gate of the first field-effect transistor, the coupling path including a diode. The switch further includes an adjustable impedance network connected between the body of the first field-effect transistor and a ground reference, the adjustable impedance network being configured to reduce radio-frequency distortion in the first field-effect transistor.
1. A radio-frequency switch comprising:
a first field-effect transistor disposed between a first node and a second node, the first field-effect transistor having a source, a drain, a gate, and a body;
a coupling path connected between the body of the first field-effect transistor and the gate of the first field-effect transistor, the coupling path including a diode; and
an adjustable impedance network connected between the body of the first field-effect transistor and a ground reference, the adjustable impedance network being configured to reduce radio-frequency distortion in the first field-effect transistor.
2. The radio-frequency switch of claim 1 wherein the adjustable impedance network is configured to present a first impedance when the first field-effect transistor is transmitting a signal having a first frequency and present a second impedance when the first field-effect transistor is transmitting a signal having a second frequency higher than the first frequency.
3. The radio-frequency switch of claim 1 wherein the first field-effect transistor is a silicon-on-insulator field-effect transistor.
4. The radio-frequency switch of claim 1 wherein the adjustable impedance network includes a second field-effect transistor having a gate, a drain, and a source.
5. The radio-frequency switch of claim 4 wherein the second field-effect transistor is connected at one of the drain or source of the second field-effect transistor to the body of the first field-effect transistor and connected at the other of the drain or the source of the second field-effect transistor to the ground reference.
6. The radio-frequency switch of claim 4 wherein the second field-effect transistor is operable to provide a desired impedance for reducing undesired radio-frequency distortion in the first field-effect transistor at a frequency of operation.
7. The radio-frequency switch of claim 4 wherein the adjustable impedance network includes one or more resistors connected in series with the second field-effect transistor.
8. The radio-frequency switch of claim 4 wherein the adjustable impedance network includes one or more capacitors connected in series with the second field-effect transistor.
9. The radio-frequency switch of claim 1 wherein the adjustable impedance network includes a capacitor.
10. The radio-frequency switch of claim 9 wherein the capacitor is connected at a first end to the body of the first field-effect transistor and at a second end to the ground reference.
11. The radio-frequency switch of claim 1 wherein the adjustable impedance network includes a capacitor connected in series with an inductor.
12. The radio-frequency switch of claim 1 wherein the adjustable impedance network includes a plurality of capacitors configured to be selectively coupled to the body of the first field-effect transistor using a network of switches.
13. A radio-frequency switch module comprising:
a packaging substrate configured to receive a plurality of components;
a semiconductor die mounted on the packaging substrate, the semiconductor die including a first field-effect transistor having a gate, a drain, a source, and a body;
a coupling path connected between the body of the first field-effect transistor and one of the source, the drain, and the gate of the first field-effect transistor, the coupling path including a diode; and
an impedance control circuit connected between the body of the first field-effect transistor and a ground reference, the impedance control circuit being configured to reduce radio-frequency distortion in the first field-effect transistor.
14. The radio-frequency switch module of claim 13 wherein the impedance control circuit includes a second field-effect transistor having a gate, a drain, and a source.
15. The radio-frequency switch module of claim 14 wherein the second field-effect transistor is connected at one of the drain or source of the second field-effect transistor to the body of the first field-effect transistor.
16. The radio-frequency switch module of claim 13 wherein the impedance control circuit includes a capacitor connected to the body of the first field effect transistor.
17. The radio-frequency switch module of claim 13 wherein the impedance control circuit includes a capacitor connected in series with an inductor.