Methods and apparatus for a continuous time linear equalizer
Various embodiments of the present technology comprise a method and apparatus for a continuous time linear equalizer (CTLE). In various embodiments, the CTLE comprises a cross-coupled transistor pair that operates as a negative impedance converter. The CTLE produces a transfer function that provides high gain peaking at a high frequency without increasing the size of the die area and/or the power supply level.
1. A continuous time linear equalizer circuit, comprising:
a differential transistor pair;
a cross-coupled circuit, connected in parallel with the differential transistor pair, comprising:
a first transistor; and
a second transistor;
wherein the first and second transistors are cross-coupled with each other; and
an RC network connected in parallel with the cross-coupled circuit.
2. The continuous time linear equalizer circuit according to claim 1 , wherein the RC network comprises a resistor connected in parallel with a capacitor.
3. The continuous time linear equalizer circuit according to claim 1 , wherein:
each of the first and second transistors comprise a bipolar transistor; and
the differential transistor pair comprises two bipolar transistors.
4. The continuous time linear equalizer circuit according to claim 3 , wherein:
the continuous time linear equalizer circuit is connected to a power supply having a minimum voltage of approximately 2.5 volts; and
the continuous time linear equalizer circuit has a transfer function comprising a peak at a frequency above 5 giga hertz and a gain above 15 decibels.
5. The continuous time linear equalizer circuit according to claim 1 , wherein:
each of the first and second transistors comprise a metal-oxide semiconductor field-effect transistor; and
the differential transistor pair comprises two metal-oxide semiconductor field-effect transistors.
6. The continuous time linear equalizer circuit according to claim 5 , wherein:
the continuous time linear equalizer circuit is connected to a power supply having a minimum voltage of approximately 1.2 volts.
7. The continuous time linear equalizer circuit according to claim 1 , further comprising:
a first current source directly connected to the first transistor; and
a second current source directly connected to the second transistor.
8. The continuous time linear equalizer circuit according to claim 1 , wherein:
the first transistor is directly connected to a transistor of the differential transistor pair; and
the second transistor is directly connected to a remaining transistor of the differential transistor pair.
9. A method for compensating for losses of high-frequency components in an analog signal, comprising:
providing a continuous time equalizer circuit, comprising:
a differential transistor pair;
a cross-coupled circuit, connected in parallel with the differential transistor pair, comprising a first transistor cross-coupled with a second transistor; and
applying a voltage range from approximately 1.2 volts to approximately 2.5 volts to the continuous time equalizer circuit.
10. The method according to claim 9 , wherein the continuous time equalizer circuit further comprises an adaptive control circuit connected in parallel with the cross-coupled circuit and configured to control a peaking gain and a frequency gain according to a control voltage.
11. The method according to claim 9 , wherein the continuous time equalizer circuit has a transfer function comprising a peak having a frequency above 5 gigahertz and a gain above 15 decibels.
12. A communication system having a transmitter and a receiver, comprising:
an equalizer circuit, connected between the transmitter and the receiver, comprising:
a differential transistor pair;
a cross-coupled circuit connected to the differential transistor pair, comprising:
a first transistor; and
a second transistor;
wherein the first and second transistors are cross-coupled with each other;
a first current source connected to a terminal of the first transistor; and
a current source connected to a terminal of the second transistor.
13. The communication system according to claim 12 , wherein the equalizer circuit further comprises an RC network connected in parallel with the cross-coupled circuit, the RC network comprises a capacitor connected in parallel with a resistor.
14. The communication system according to claim 12 , wherein the equalizer circuit further comprises an adaptive control circuit connected in parallel with the cross-coupled circuit and configured to control a peaking gain and a frequency gain according to a control voltage.
15. The communication system according to claim 12 , wherein the equalizer circuit has a transfer function comprising a peak having a frequency above 5 gigahertz and a gain above 15 decibels.
16. The communication system according to claim 12 , wherein:
the first transistor is directly connected to a transistor of the differential transistor pair; and
the second transistor is directly connected to a remaining transistor of the differential transistor pair.
17. The communication system according to claim 12 , wherein:
each of the first and second transistors comprise a bipolar transistor; and
the differential transistor pair comprises two bipolar transistors.
18. The communication system according to claim 17 , wherein the equalizer circuit is connected to a power supply having a minimum voltage of approximately 2.5 volts.
19. The communication system according to claim 12 , wherein:
each of the first and second transistors comprise a metal-oxide semiconductor field-effect transistor; and
the differential transistor pair comprises two metal-oxide semiconductor field-effect transistors.
20. The communication system according to claim 19 , wherein the equalizer circuit is connected to a power supply having a minimum voltage of approximately 1.2 volts.