RF Switch Gate Control
In one implementation, a switching circuit includes a pass switch including group III-V, for example III-Nitride, transistors coupled between an input of the switching circuit and an output of the switching circuit. The switching circuit further includes a shunt switch configured to ground the input of the switching circuit while the pass switch is disabled. The switching circuit also includes a gate control transistor configured to reduce resistance between a control terminal of the pass switch and/or the shunt switch and gate of the group III-V transistor of the pass switch and/or the shunt switch so as to enable and disable the pass switch and/or shunt switch. The gate control transistor can be coupled across a gate resistor of the pass switch and/or the shunt switch. The gate control transistor can reduce the resistance in order to lower the OFF state impedance of the pass switch and/or the shunt switch.
1 . An RF switch comprising:
at least one transistor;
a gate resistor and a gate control transistor;
wherein said gate control transistor is parallel connected across said gate resistor;
and wherein said gate control transistor is configured to reduce resistance between a control terminal of said RF switch and a gate of said at least one transistor when said at least one transistor is in an OFF state.
2 . The RF switch of claim 1 , wherein said gate resistor has a resistance greater than approximately 20 kilo-ohms
3 . The RF switch of claim 1 , wherein said gate control transistor reduces said resistance to improve isolation of said RF switch.
4 . The RF switch of claim 1 , wherein said at least one transistor is a group III-V High Electron Mobility Transistor (HEMT).
5 . The RF switch of claim 1 , wherein said at least one transistor is a depletion mode transistor.
6 . The RF switch of claim 1 , wherein said at least one transistor is selected from the group consisting of a CMOS transistor and a LDMOS transistor.
7 . The RF switch of claim 1 , wherein said gate control transistor is a P channel transistor.
8 . The RF switch of claim 1 wherein said at least one transistor comprises two or more series connected transistors.
9 . The RF switch of claim 5 , wherein said gate control transistor has a threshold voltage that is approximately equal to a pinch-off voltage of said depletion mode transistor.
10 . The RF switch of claim 1 , wherein said gate control transistor and said gate resistor are monolithically integrated.
11 . The RF switch of claim 1 , wherein one or more of said at least one transistors and either said gate control transistor and/or said gate resistor are monolithically integrated.
12 . A switching circuit comprising:
a pass switch comprising at least one transistor coupled between an input of said switching circuit and an output of said switching circuit;
a shunt switch configured to ground said input of said switching circuit when said pass switch is disabled;
a gate control transistor configured to reduce resistance between a control terminal of said pass switch and gate of said at least one transistor of said pass switch so as to improve isolation of said pass switch.
13 . The switching circuit of claim 12 , wherein said gate control transistor is coupled across a gate resistor of said pass switch.
14 . The switching circuit of claim 13 , wherein said gate resistor has a resistance greater than approximately 20 kilo-ohms.
15 . The switching circuit of claim 12 , wherein said gate control transistor reduces said resistance to improve isolation of said switching circuit.
16 . The switching circuit of claim 12 , wherein said gate control transistor is a group IV transistor.
17 . The switching circuit of claim 12 , wherein said shunt switch comprises at least one group III-V transistor.
18 . The switching circuit of claim 12 , further comprising another gate control transistor configured to reduce resistance between a control terminal of said shunt switch and gate of at least one transistor of said shunt switch so as to improve isolation of said shunt switch.
19 . The switching circuit of claim 12 , wherein said gate control transistor is a P channel transistor.
20 . The switching circuit of claim 12 , wherein said at least one transistor of said pass switch is a group transistor.
21 . The switching circuit of claim 20 , wherein said gate control transistor has a threshold voltage that is approximately equal to a pinch-off voltage of said group III-V transistor.
22 . The switching circuit of claim 12 , wherein said at least one transistor of said pass switch is selected from the group consisting of a CMOS transistor and a LDMOS transistor.