Main-auxiliary field-effect transistor structures for radio frequency applications
Disclosed herein are switching or other active FET configurations that implement a main-auxiliary branch design. Such designs include a circuit assembly for performing a switching function that includes a branch including a main path in parallel with an auxiliary path. The circuit assembly also includes a gate bias network connected to the main path and to the auxiliary path, the main path and the auxiliary path each having different structures that are configured to improve linearity of the switching function.
1. A radio-frequency (RF) module comprising:
a packaging substrate configured to receive a plurality of devices; and
a circuit assembly mounted on the packaging substrate and implemented in a series arm of a multi-pole, multi-throw switch, the circuit assembly including a branch including a main path in parallel with an auxiliary path, and a gate bias network connected to the main path and to the auxiliary path, the main path and the auxiliary path each having different structures that are configured to improve linearity of the switching function upon application of a single gate bias signal that biases the main path in a strong inversion region and that biases the auxiliary path in a weak inversion region.
2. The circuit assembly RF module of claim 1 wherein the gate bias network is configured to bias the auxiliary path to generate third-order harmonics or third-order intermodulation products that are opposite in phase to third-order harmonics or third-order intermodulation products generated by the main path.
3. The RF module of claim 1 wherein the different structures include different well implants.
4. The RF module of claim 1 wherein the different structures include different halo implants.
5. The RF module of claim 1 wherein the different structures include different device geometries.
6. The RF module of claim 1 wherein the different structures include different gate oxide thicknesses.
7. The RF module of claim 1 wherein the different structures include different buried oxide (BOX) layer thickness.
8. The RF module of claim 1 wherein the different structures include different silicon thickness.
9. The RF module of claim 1 further comprising a body bias network connected to both the main path and the auxiliary path.
10. The RF module of claim 1 wherein the main path and the auxiliary path are part of a multi-finger device.