Transistor-based radio frequency (RF) switch
Disclosed is a transistor-based switch having an N number of main field-effect transistors (FETs) stacked in series such that a first terminal of a first main FET of the N number of main FETs is coupled to a first end node and a second terminal of an Nth main FET of the N number of main FETs is coupled to a second end node, wherein N is a finite number greater than five. The transistor-based switch further includes a gate bias network having a plurality of gate resistors, wherein individual ones of the plurality of gate resistors are coupled to gate terminals of the N number of main FETs. A common gate resistor is coupled between a gate control input and a gate control node of the plurality of gate resistors, and a capacitor is coupled between the gate control node and a switch path node of the main FETs.
1. A transistor-based radio frequency (RF) switch comprising:
an N number of main field-effect transistors (FETs) stacked in series such that a first terminal of a first main FET of the N number of main FETs is coupled to a first end node and a second terminal of an Nth main FET of the N number of main FETs is coupled to a second end node, wherein N is a finite number greater than five;
a gate bias network comprising:
a plurality of gate resistors, wherein individual ones of the plurality of gate resistors are coupled between gate terminals of adjacent ones of the N number of main FETs;
a common gate resistor coupled between a gate control input and a gate control node of the plurality of gate resistors; and
a first capacitor coupled between the gate control node and a switch path node of the N number of main FETs.
2. The transistor-based RF switch of claim 1 further including a plurality of speed-up FETs, wherein individual ones of the plurality of speedup FETs are coupled across corresponding ones of the plurality of gate resistors such that the plurality of gate resistors are shorted when the plurality of speedup FETs are in an ON state.
3. The transistor-based RF switch of claim 2 wherein the N number of main FETs are N-type and the plurality of speed-up FETs are P-type.
4. The transistor-based RF switch of claim 1 wherein the switch path node is located between a first group of the N number of main FETs coupled between the first end node and the switch path node and a second group of the N number of main FETs coupled between the switch path node and the second end node.
5. The transistor-based RF switch of claim 4 wherein the first group and the second group are made up of an equal number of the N number of main FETs.
6. The transistor-based RF switch of claim 5 wherein both a nearest one of the plurality of gate resistors to the first end node and a nearest one of the plurality of gate resistors to the second end node have within ±10% of half of a resistance value of each remaining one of the plurality of gate resistors.
7. The transistor-based RF switch of claim 1 wherein the switch path node is coupled to the first terminal of the first main FET.
8. The transistor-based RF switch of claim 7 further including a second capacitor coupled between the second terminal of the Nth main FET and one of the gate terminals associated with the Nth main FET through one of the plurality of gate resistors nearest to the second end node.
9. The transistor-based RF switch of claim 1 further including a second capacitor coupled between the gate control node and a second switch path node, wherein N is an odd number and the middle one of the N number of main FETs is coupled directly between the switch path node and the second switch path node.
10. The transistor-based RF switch of claim 1 wherein a first group of the N number of main FETs has source terminals that are closer to the first end node and drain terminals that are closer to the second end node and a second group of the N number of main FETs has drain terminals that are closer to the first end node and source terminals that are closer to the second end node, wherein the first group is equal in number to the second group.
11. The transistor-based RF switch of claim 10 wherein the first group comprises half of the N number of main FETs, wherein N is an even number.
12. The transistor-based RF switch of claim 10 wherein each of the first group of the N number of main FETs is coupled to an adjacent one of the second group of the N number of main FETs.
13. The transistor-based RF switch of claim 1 wherein the first capacitor is a metal-insulator-metal type capacitor.
14. The transistor-based RF switch of claim 1 wherein capacitance of the first capacitor is between 0.1 picofarad and 10 picofarads.
15. The transistor-based RF switch of claim 1 where resistance of the common gate resistor is between 2 kΩ and 100 kΩ.
16. The transistor-based RF switch of claim 15 wherein the resistance of each one of the plurality of gate resistors is equal to the resistance of the common gate resistor within ±10%.
17. The transistor-based RF switch of claim 1 further comprising:
a body bias network having a plurality of body resistors, wherein individual ones of the plurality of body resistors are coupled to body terminals of the N number of main FETs, and a common body resistor is coupled between a body control input and a body control node of the plurality of body resistors; and
a second capacitor coupled between the body control node and the switch path node of the N number of main FETs.
18. The transistor-based RF switch of claim 1 further including a plurality of source-to-drain resistors wherein individual ones of the plurality of source-to-drain resistors are coupled between drain terminals and source terminals of individual ones of the N number of main FETs.
19. The transistor-based RF switch of claim 1 wherein the N number of main FETs are of the silicon-on-insulator type.