Inductive drain and/or body ladders in RF switch stacks
Methods and devices to reduce the gate-induced drain/body leakage current (GIDL) generated in FET switch stacks when in OFF state are disclosed. Such devices include inductors as part of bias networks coupled with drain/source terminals and/or body terminals of the transistors within the switch stack. Hybrid approaches where resistors in combination with inductors are implemented as part the bias network are also described.
1. A switch stack comprising:
a plurality of field-effect transistors (FETs) arranged in series and connected at one end to a first node and at another end to a second node;
a drain bias ladder comprising one or more drain inductors coupled across drain and source terminals of corresponding one or more first FETs of the plurality of FETs, and
one or more drain resistors in series with the one or more drain inductors, the one or more drain resistors coupled across drain and source terminals of corresponding one or more second FETs of the plurality of FETs, the one or more second FETs being different from the one or more first FETs.
2. The switch stack of claim 1 , wherein the one or more first FETs comprise a first FET disposed in a middle of the switch stack.
3. The switch stack of claim 1 , wherein the one or more first FETs comprise a FET other than a top FET being the closest to the first node or a bottom FET being the closest to the second node.
4. The switch stack of claim 1 , wherein the one or more first FETs or the one or more second FETs comprise FETs other than a top FET being the closest to the first node or a bottom FET being the closest to the second node.
5. A switch stack comprising:
a plurality of field-effect transistors (FETs) arranged in series and connected at one end to a first node and at another end to a second node;
a drain bias ladder comprising one or more drain inductors coupled across drain and source terminals of corresponding one or more first FETs of the plurality of FETs, and a body bias ladder comprising one or more body inductors, wherein each of the one or more body inductors is coupled across body terminals of a corresponding pair of first adjacent FETs.
6. The switch stack of claim 1 implemented in a shunt or a series configuration.
7. The switch stack of claim 1 configured to operate within a frequency range of 30 GHz to 300 GHz.
8. The switch stack of claim 1 , wherein the one or more drain inductors are coupled across drain and source terminals of corresponding one or more first FETs of the plurality of FETs via respective resistors.
9. A switch stack comprising:
a plurality of field-effect transistors (FETs) arranged in series and connected at one end to a first node and at another end to a second node; and
a drain bias ladder comprising one or more drain inductors coupled across drain and source terminals of corresponding one or more first FETs of the plurality of FETs, wherein one or more of drain inductor values are selected to resonate with the corresponding one or more first FETs off capacitance within a band of operation.
10. The switch stack of claim 5 , wherein a first end of each of the one or more body inductors is coupled to a body terminal of a first corresponding FET via a first resistor, and a second end of each of the one or more body inductors is connected to a body terminal of a second corresponding FET via a second resistor, and wherein the first and the second corresponding FETs are adjacent FETs.
11. The switch stack of claim 5 , wherein a series combination of a first body inductor of the one or more body inductors with a first series capacitor is coupled across the first node and a body terminal of a top FET, the top FET being closest to the first node, or a series combination of a second body inductor of the one or more body inductors with a second series capacitor is coupled across the second node and a body terminal of a bottom FET, the bottom FET being the closest to the second node.
12. The switch stack of claim 5 , further comprising one or more drain resistors in series with the one or more drain inductors, the one or more drain resistors coupled across drain and source terminals of corresponding one or more second FETs of the plurality of FETs, the one or more second FETs being different from the one or more first FETs.
13. The switch stack of claim 5 , wherein the one or more first FETs comprise a first FET disposed in a middle of the switch stack.
14. The switch stack of claim 5 , wherein the one or more first FETs comprise a FET other than a top FET being the closest to the first node or a bottom FET being the closest to the second node.
15. The switch stack of claim 12 , wherein the one or more first FETs or the one or more second FETs comprise FETs other than a top FET being the closest to the first node or a bottom FET being the closest to the second node.
16. The switch stack of claim 5 implemented in a shunt or a series configuration.
17. The switch stack of claim 5 configured to operate within a frequency range of 30 GHz to 300 GHz.
18. The switch stack of claim 5 , wherein:
the body bias ladder further comprises one or more body resistors in series with the one or more body inductors;
each of the one or more body resistors is coupled across body terminals of a corresponding pair of second adjacent FETs, and
any two pairs of adjacent FETs including one pair from the first adjacent FETs and one pair from the second adjacent FETs have at most one FET in common.
19. The switch stack of claim 5 , wherein:
body terminals of one or more pairs of second adjacent FETs are tied together, and
any two pairs of adjacent FETs including one pair from the first adjacent FETs and one pair from the second adjacent FETs have at most one FET in common.
20. The switch stack of claim 9 , wherein the one or more first FETs comprise a first FET disposed in a middle of the switch stack.
21. The switch stack of claim 9 , wherein the one or more first FETs comprise a FET other than a top FET being the closest to the first node or a bottom FET being the closest to the second node.