RF switches having increased voltage swing uniformity
Radio-frequency (RF) switch circuits are disclosed providing uniform voltage swing across a transmit switch for improved device performance. A switching circuit includes a switch having field effect transistors (FETs) defining an RF signal path between the input port and the output port, the switch configured to be capable of being in a first state corresponding to the input and output ports being electrically connected so as to allow passage of the RF signal therebetween, and a second state corresponding to the input and output ports being electrically isolated. The switching circuit includes a voltage distribution circuit configured to reduce voltage distribution variation across the switch, including one or more elements coupled to a selected body node of one or more FETs so as to reduce voltage distribution variation across the switch when the switch is in the first state and encountered by an RF signal at the input port.
1. A switching circuit, comprising:
an input port configured to receive a radio-frequency (RF) signal;
an output port configured to output the RF signal;
a switch including a first field effect transistor (FET) having a first body node and a second FET having a second body node, the first and second FETs defining an RF signal path between the input port and the output port, the switch configured to be capable of being in first and second states, the first state corresponding to the input and output ports being electrically connected so as to allow passage of the RF signal therebetween, the second state corresponding to the input and output ports being electrically isolated; and
a voltage distribution circuit configured to reduce voltage distribution variation across the switch, the voltage distribution circuit including a connection path connected between the first body node and the second body node, the connection path including a first resistor and a first capacitor connected in series with the first resistor, the voltage distribution circuit further including a resistive network connected between the first body node and the second body node, the resistive network including a bias node connected between third and of the resistive network.
2. The switching circuit of claim 1 wherein the voltage distribution circuit further includes a feed-forward capacitive element configured to couple the RF signal to the first body node.
3. The switching circuit of claim 2 wherein the feed-forward capacitive element is configured to couple the RF signal to the first body node through a source or drain of the first FET.
4. The switching circuit of claim 1 wherein the voltage distribution circuit further includes a feed-forward capacitive element connected in series to a resistive element and configured to couple the RF signal to the first body node.
5. The switching circuit of claim 1 wherein the voltage distribution circuit further includes a resistive element coupled to a gate node of the first FET to thereby enable floating of the gate node of the FET.
6. A packaged module for a radio-frequency (RF) device, the module comprising:
a packaging substrate; and
an integrated circuit (IC) formed on a semiconductor die and mounted on the packaging substrate, the IC including a switch having a first field effect transistor (FET) having a first body node and a second FET having a second body node, the first and second FETs defining an RF signal path between an input port and an output port, the IC further including a voltage distribution circuit coupled to the switch and configured to reduce voltage distribution variation across the switch when the switch is in an ON state and encountered by a respective RF signal at the input port, the voltage distribution circuit including a connection path connected between the first body node and the second body node, the connection path including a first resistor and a first capacitor connected in series with the first resistor, the voltage distribution circuit further including a resistive network connected between the first body node and the second body node, the resistive network including a bias node connected between third and of the resistive network.
7. The packaged module of claim 6 further comprising at least one connection configured to facilitate passage of signals to and from the switch.
8. The packaged module of claim 6 further comprising a packaging structure configured to provide protection for the switch.