Low power amplitude modulation detector
View Patent ↗An AM demodulator using totem pole complementary metal oxide semiconductor transistors having a feedback to provide a common gate voltage of approximately half that across the transistors in the totem pole. The AM demodulator used in a hearing assistance device and in a programmer of a hearing assistance device.
1. An apparatus comprising:
a p-channel metal oxide semiconductor (PMOS) transistor having a first drain and further having a first source connected to a first load at an output node, the first load having another connection to a first voltage reference; and
an n-channel metal oxide semiconductor (NMOS) transistor having a second drain connected to the first drain of the PMOS transistor at a feedback node, the NMOS transistor having a second source connected to a second load, the second load having another connection to a second voltage reference,
wherein the first gate of the PMOS transistor and the second gate of the NMOS transistor are connected to a coupling capacitor, the coupling capacitor receiving radio frequency input signals and wherein the first gate and second gate receive a feedback from the feedback node.
2. The apparatus of claim 1 , wherein the first load is a resistor.
3. The apparatus of claim 1 , wherein the first load is a transistor.
4. The apparatus of claim 1 , wherein the second load is a resistor.
5. The apparatus of claim 1 wherein the second load is a transistor.
6. The apparatus of claim 1 , wherein the feedback comprises a signal passing through a third load.
7. The apparatus of claim 6 , wherein the third load is a resistor.
8. The apparatus of claim 6 , wherein the third load is a transistor.
9. The apparatus of claim 1 , wherein the PMOS transistor and NMOS transistor are complementary metal oxide semiconductor (CMOS) transistors.
10. The apparatus of claim 1 , wherein the first voltage reference is a positive supply voltage and the second voltage reference is a ground.
11. The apparatus of claim 1 , wherein: the PMOS transistor and NMOS transistor are complementary metal oxide semiconductor (CMOS) transistors; the feedback includes a third load; the first load, second load, and third load are resistor-connected transistors; and the PMOS transistor, NMOS transistor, first load, second load, and third load are fabricated in an integrated circuit.
12. The apparatus of claim 11 , wherein the first voltage reference is a positive supply voltage and the second voltage reference is a ground.
13. An apparatus, comprising:
a microphone connected to a controller;
a receiver connected to the controller; and
an antenna connected to communication electronics, the communication electronics connected to the controller and comprising:
a p-channel metal oxide semiconductor (PMOS) transistor having a first drain and further having a first source connected to a first load at an output node, the first load having another connection to a first voltage reference; and
an n-channel metal oxide semiconductor (NMOS) transistor having a second drain connected to the first drain of the PMOS transistor at a feedback node, the NMOS transistor having a second source connected to a second load, the second load having another connection to a second voltage reference,
wherein the first gate of the PMOS transistor and the second gate of the NMOS transistor are connected to a coupling capacitor, the coupling capacitor receiving radio frequency input signals and wherein the first gate and second gate receive a feedback from the feedback node.
14. The apparatus of claim 13 , wherein: the PMOS transistor and NMOS transistor are complementary metal oxide semiconductor (CMOS) transistors; the feedback includes a third load; the first load, second load, and third load are resistor-connected transistors; and the PMOS transistor, NMOS transistor, first load, second load, and third load are fabricated in an integrated circuit.
15. The apparatus of claim 14 , wherein the first voltage reference is a positive supply voltage and the second voltage reference is a ground.
16. An apparatus, comprising:
a memory connected to a controller;
an input device connected to the controller; and
an antenna connected to communication electronics, the communication electronics connected to the controller and comprising:
a p-channel metal oxide semiconductor (PMOS) transistor having a first drain and further having a first source connected to a first load at an output node, the first load having another connection to a first voltage reference; and
an n-channel metal oxide semiconductor (NMOS) transistor having a second drain connected to the first drain of the PMOS transistor at a feedback node, the NMOS transistor having a second source connected to a second load, the second load having another connection to a second voltage reference,
wherein the first gate of the PMOS transistor and the second gate of the NMOS transistor are connected to a coupling capacitor, the coupling capacitor receiving radio frequency input signals and wherein the first gate and second gate receive a feedback from the feedback node.
17. The apparatus of claim 16 , wherein: the PMOS transistor and NMOS transistor are complementary metal oxide semiconductor (CMOS) transistors; the feedback includes a third load; the first load, second load, and third load are resistor-connected transistors; and the PMOS transistor, NMOS transistor, first load, second load, and third load are fabricated in an integrated circuit.
18. The apparatus of claim 17 , wherein the first voltage reference is a positive supply voltage and the second voltage reference is a ground.
19. A method, comprising:
receiving an amplitude modulated signal; and
processing the amplitude modulated signal with a capacitively coupled demodulator comprising a totem pole configuration of complementary metal oxide semiconductor transistors including providing a feedback signal to a gate of each of the complementary metal oxide semiconductor transistors to generate a demodulated signal.
20. The method of claim 19 , wherein the step of receiving comprises filtering the amplitude modulated signal.