Method and circuit to isolate body capacitance in semiconductor devices
Disclosed is an amplifying circuit and method. In one embodiment, an amplifying circuit, includes: a common-gate (CG) amplifier, wherein the CG amplifier comprises a first transistor, wherein source terminal and body terminal of the first transistor is coupled together through a first resistor.
1. An amplifying circuit, comprising:
a common-gate (CG) amplifier, wherein the CG amplifier comprises a first transistor, wherein
source terminal and body terminal of the first transistor are coupled together through a first resistor,
the source terminal and the body terminal of the first transistor are also coupled together through a first diode, and
drain terminal and the body terminal of the first transistor are coupled together through a second diode; and
a common-source (CS) amplifier, wherein the CS amplifier comprises a second transistor, wherein source terminal and body terminal of the second transistor are coupled directly to each other, and wherein the source terminal of the first transistor is coupled directly to drain terminal of the second transistor.
2. The circuit of claim 1 , wherein
the first diode is formed between an N region of the source terminal of the first transistor and a P-well region in which the body terminal of the first transistor is fabricated; and
the second diode is formed between an N region of the drain terminal of the first transistor and the P-well region.
3. The circuit of claim 1 , wherein the first transistor comprises one of the following: an N-type metal-oxide-semiconductor (NMOS) transistor and a P-type MOS (PMOS) transistor.
4. The circuit of claim 1 , further comprising:
a gate insulator; and
a conductive gate formed on top of the gate insulator.
5. The circuit of claim 1 , wherein the CG amplifier is fabricated in a deep N well of a P-type substrate.
6. The circuit of claim 1 , wherein the CG amplifier is fabricated in a P well of an N-type substrate.
7. The circuit of claim 1 , wherein the second transistor is further configured to receive an input voltage at the gate terminal of the CS amplifier through a capacitor.
8. A power amplifying circuit, comprising:
a common-gate (CG) amplifier, wherein the CG amplifier comprises a first transistor, wherein
source terminal and body terminal of the first transistor are coupled together through a first resistor,
the source terminal and the body terminal of the first transistor are also coupled together through a first diode,
drain terminal and the body terminal of the first transistor are coupled together through a second diode, and
the body terminal of the first transistor is coupled to ground; and
a common-source (CS) amplifier, wherein the CS amplifier comprises a second transistor that is connected in series with the first transistor, wherein source terminal and body terminal of the second transistor are coupled directly to each other, and wherein the source terminal of the first transistor is coupled directly to drain terminal of the second transistor.
9. The circuit of claim 8 , wherein the first and second transistors each comprises one of the following: an N-type metal-oxide-semiconductor (NMOS) transistor and a P-type MOS (PMOS) transistor.
10. The circuit of claim 8 , wherein the second transistor is further configured to receive an input voltage at the gate terminal of the CS amplifier through a capacitor.
11. The circuit of claim 8 , wherein the gate terminal of the second transistor is coupled to an input voltage through a capacitor and is further coupled to an external bias voltage through a second resistor.
12. The circuit of claim 8 , further comprising:
a gate insulator; and
a conductive gate formed on top of the gate insulator.
13. The circuit of claim 8 , wherein the CG amplifier is fabricated in a deep N well of a P-type substrate.
14. The circuit of claim 8 , wherein the CG amplifier is fabricated in a P well of an N-type substrate.
15. A method for operating a power amplifying circuit, comprising:
providing a first voltage on gate terminal of a common-gate (CG) amplifier;
receiving a second voltage on gate terminal of a common-source (CS) amplifier so as to generate a first output current on the CS amplifier; and
generating a second output current on the CG amplifier, wherein:
the CG amplifier comprises a first transistor,
source terminal and body terminal of the first transistor are coupled together through a first resistor,
the source terminal and the body terminal of the first transistor are also coupled together through a first diode,
drain terminal and the body terminal of the first transistor are coupled together through a second diode,
the CS amplifier comprises a second transistor that is connected in series with the first transistor,
source terminal and body terminal of the second transistor are coupled directly to each other, and
the source terminal of the first transistor is coupled directly to drain terminal of the second transistor.
16. The method of claim 15 , wherein the first and second transistors each comprises one of the following: an N-type metal-oxide-semiconductor (NMOS) transistor and a P-type MOS (PMOS) transistor.
17. The method of claim 15 , further comprising:
a gate insulator; and
a conductive gate formed on top of the gate insulator.
18. The method of claim 15 , wherein the CG amplifier is fabricated in a deep N well of a P-type substrate.
19. The method of claim 15 , wherein the CG amplifier is fabricated in a P well of an N-type substrate.
20. The method of claim 15 , wherein the second transistor is further configured to receive an input voltage at the gate terminal of the CS amplifier through a capacitor.