Push-pull transimpedance amplifier
View Patent ↗The present disclosure relates to a push-pull transimpedance amplifier (TIA) that receives a push-pull radio frequency (RF) input current signal having a push current and a pull current and includes a common-emitter pre-amplifier and a dynamic feedback current source (DFCS). The common-emitter pre-amplifier receives at least a portion of the push current and provides a first RF signal based on amplifying the push-pull RF input current signal. The DFCS provides at least a portion of the pull current based on the first RF signal. The push-pull TIA may operate at high data rates, may have high input sensitivity, may provide linear amplification of the push-pull RF input current signal, or any combination thereof. The push-pull TIA may provide an RF output signal based on amplifying the push-pull RF input current signal.
1. A push-pull transimpedance amplifier (TIA) adapted to receive a push-pull radio frequency (RF) input current signal having a push current and a pull current, and comprising:
a common emitter pre-amplifier adapted to:
receive at least a portion of the push current; and
provide a first RF signal based on amplifying the push-pull RF input current signal; and
a dynamic feedback current source (DFCS) adapted to provide at least a portion of the pull current based on the first RF signal and directly coupled between the TIA input and the first output,
wherein the push-pull TIA is adapted to provide an RF output signal based on amplifying the push-pull RF input current signal.
2. The push-pull TIA of claim 1 wherein:
the push-pull TIA comprises a TIA input adapted to receive the push-pull RF input current signal; and
the common emitter pre-amplifier comprises:
a pre-amplifier input coupled to the TIA input and adapted to receive the at least the portion of the push current; and
a first output adapted to provide the first RF signal.
3. The push-pull TIA of claim 2 wherein the DFCS detects a polarity of the first RF signal and provides the at least the portion of the pull current based on the detected polarity of the first RF signal.
4. The push-pull TIA of claim 3 wherein the DFCS comprises a DFCS transistor element comprising:
a base coupled to the first output;
an emitter coupled to the pre-amplifier input; and
one selected from a group consisting of an NPN transistor element and an N-type metal oxide semiconductor (NMOS) transistor element.
5. The push-pull TIA of claim 4 wherein the DFCS further comprises:
a first DFCS resistive element coupled between the base of the DFCS transistor element and the first output; and
a second DFCS resistive element coupled between the emitter of the DFCS transistor element and the pre-amplifier input.
6. The push-pull TIA of claim 4 wherein the DFCS further comprises a first DFCS resistive element coupled between the emitter of the DFCS transistor element and the pre-amplifier input.
7. The push-pull TIA of claim 2 further comprising a direct current (DC) restore feedback network coupled between the pre-amplifier input and an output of the common emitter pre-amplifier, such that the DC restore feedback network is adapted to provide DC leveling of the common emitter pre-amplifier as a magnitude of the push-pull RF input current signal increases.
8. The push-pull TIA of claim 7 wherein the DC restore feedback network comprises:
a detector coupled to the output of the common emitter pre-amplifier and adapted to receive and detect an amplified signal from the output of the common emitter pre-amplifier;
DC control circuitry coupled between the detector and a first transistor element and adapted to control the first transistor element based on a magnitude of the amplified signal; and
the first transistor element comprising a collector, which is coupled to the pre-amplifier input.
9. The push-pull TIA of claim 7 wherein the output of the common emitter pre-amplifier is the first output and an amplified signal from the output of the common emitter pre-amplifier is the first RF signal.
10. The push-pull TIA of claim 7 wherein the output of the common emitter pre-amplifier is a second output.
11. The push-pull TIA of claim 2 wherein the common emitter pre-amplifier comprises:
a first stage having an input, which is coupled to the pre-amplifier input, and an output, which is coupled to the first output; and
a second stage having an input, which is coupled to the first output, and one output, which is coupled to a second output of the common emitter pre-amplifier,
wherein the first stage amplifies the push-pull RF input current signal to provide the first RF signal.
12. The push-pull TIA of claim 11 wherein:
the first stage comprises a first stage transistor element comprising:
a base coupled to the pre-amplifier input; and
a collector coupled to the first output; and
the second stage comprises a second stage transistor element comprising:
a base coupled to the first output; and
a collector coupled to the second output,
wherein the first stage transistor element is a common emitter NPN transistor element.
13. The push-pull TIA of claim 12 wherein the second stage further comprises:
a second stage resistive element coupled between the first output and the base of the second stage transistor element; and
a feedback resistive element coupled between the base of the second stage transistor element and the collector of the second stage transistor element.
14. The push-pull TIA of claim 12 wherein the second stage transistor element further comprises an emitter coupled to a third output of the common emitter pre-amplifier.
15. The push-pull TIA of claim 1 wherein the push-pull TIA is adapted to provide linear amplification of the push-pull RF input current signal.
16. The push-pull TIA of claim 15 wherein the push-pull TIA is further adapted to provide non-saturated linear amplification of the push-pull RF input current signal.
17. The push-pull TIA of claim 16 wherein an operating frequency of the push-pull RF input current signal is greater than about 100 gigahertz.
18. The push-pull TIA of claim 1 wherein an operating frequency of the push-pull RF input current signal is greater than about 100 gigahertz.
19. The push-pull TIA of claim 1 wherein the push-pull TIA is adapted to operate in compression, such that a portion of the push-pull RF input current signal saturates.
20. The push-pull TIA of claim 1 wherein a push-pull photo-detector provides the push-pull RF input current signal.
21. The push-pull TIA of claim 1 further comprising a post amplifier coupled to the common emitter pre-amplifier and adapted to receive and amplify an amplified signal from the common emitter pre-amplifier to provide the RF output signal.
22. The push-pull TIA of claim 1 wherein the DFCS comprises a DFCS transistor element comprising:
a base adapted to receive the first RF signal;
an emitter adapted to provide the at least the portion of the pull current; and
one selected from a group consisting of an NPN transistor element and an N-type metal oxide semiconductor (NMOS) transistor element.
23. A method comprising:
receiving a push-pull radio frequency (RF) input current signal having a push current and a pull current;
providing a common emitter pre-amplifier associated with a push-pull transimpedance amplifier (TIA);
receiving at least a portion of the push current;
amplifying the push-pull RF input current signal to provide a first RF signal;
providing at least a portion of the pull current based on the first RF signal through a dynamic feedback current source (DFCS) directly coupled between a TIA input and a first output; and
providing an RF output signal based on amplifying the push-pull RF input current signal.