Electro-optical modulator interface

• US 9,229,250 B2
• Filed: 10/01/2013
• Issued: 01/05/2016
• Est. Priority Date: 10/11/2012
• Status: Active Grant

• Current Assignee: STMicroelectronics International N.V. (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: Minoia, Gabriele, Temporiti Milani, Enrico Stefano, Galeone, Salvatore
• Primary Examiner(s): Kim, Jung
• Application Number:
  US14/043,547
• Publication Number:
  US 20140104666A1
• Time in Patent Office: 826 Days
• US Class Current: 1/1
• CPC Class Codes: G02F 1/0121 Operation of devices; Circuit arrangements, not otherwise provided for in this subclass
• CPC Class Codes: G02F 1/225 in an optical waveguide structure
• CPC Class Codes: G02F 2201/126 push-pull
• CPC Class Codes: H03K 19/018521 of complementary type, e.g. CMOS
• CPC Class Codes: H03K 19/018528 with at least one differential stage

Abstract

A relatively high-speed, high-efficiency CMOS two branch driver core that may operate under relatively low supply voltage may include thin oxide CMOS transistors configured to generate rail-to-rail output swings larger than twice a supply voltage and without exceeding safe operating area limits. Each of the two branches may include two stacked CMOS inverter pairs configured to drive a respective load capacitance coupled between respective CMOS inverter outputs, in phase opposition to the other branch. A pre-driver circuit input with a differential modulating signal may output two synchronous differential voltage drive signals of a swing of half of the supply voltage and DC-shifted by half of the supply voltage with respect to each other and that may be applied to the respective CMOS inverter inputs of the two branches.

Claims

1. An integrated electro-optical modulator interface comprising:

a two-branch output stage comprising a plurality of thin oxide CMOS transistors configured to generate rail-to-rail output swings larger than twice a nominal limit of a supply voltage of said plurality of thin oxide CMOS transistors, each branch of said two-branch output stage comprising two stacked CMOS inverter pairs from among said plurality of thin oxide CMOS transistors;

said two stacked CMOS inverter pairs of a given branch being configured to drive a respective load capacitance, in phase opposition to the other branch; and

a pre-driver circuit configured to receive a differential modulating signal and output, to respective inputs of said two stacked CMOS inverters, two synchronous differential voltage drive signals having a swing of half the supply voltage and being DC-shifted by half of the supply voltage with respect to each other.

2. The integrated electro-optical modulator interface of claim 1, further comprising circuitry tying middle nodes of each branch of said two-branch output stage to one of respective supply voltage rails and an additional half supply voltage rail.

3. The integrated electro-optical modulator interface of claim 1, further comprising one of a lumped bypass capacitance and a distributed R-L-C structure including a plurality of lumped capacitances coupled in a low impedance signal path at a high frequency between respective supply voltage rails.

4. The integrated electro-optical modulator interface of claim 1, wherein said pre-driver circuit comprises an input impedance matching stage, a DC shifting stage coupled to said input impedance matching stage, and a signal amplification core stage coupled to said input impedance matching stage.

5. The integrated electro-optical modulator interface of claim 4, wherein said DC shifting stage comprises a plurality of capacitances configured to be pre-charged to half the supply voltage.

6. The integrated electro-optical modulator interface of claim 5, wherein said DC shifting stage further comprises a plurality of back-to-back inverter latches configured to maintain a charge of said plurality of capacitances and maintain the two synchronous differential voltage drive signals in phase opposition.

7. An electro-optical modulator interface comprising:

a two-branch output stage, each branch comprising a plurality of stacked CMOS inverter pairs;

said plurality of stacked CMOS inverter pairs of a given branch being configured to drive a respective load capacitance in phase opposition to the other branch; and

a pre-driver circuit coupled to said plurality of stacked CMOS inverter pairs and configured to generate two synchronous differential voltage drive signals having a swing of half a supply voltage and being DC-shifted by half of the supply voltage with respect to each other.

8. The electro-optical modulator interface of claim 7, further comprising circuitry coupling middle nodes of each branch of said two-branch output stage to one of respective supply voltage rails and an additional half supply voltage rail.

9. The electro-optical modulator interface of claim 7, further comprising one of a lumped bypass capacitance and a distributed R-L-C structure comprising a plurality of lumped capacitances coupled between respective supply voltage rails.

10. The electro-optical modulator interface of claim 7, wherein said pre-driver circuit comprises an input impedance matching stage, a DC shifting stage coupled to said input impedance matching stage, and a signal amplification core stage coupled to said input impedance matching stage.

11. The electro-optical modulator interface of claim 10, wherein said DC shifting stage comprises a plurality of capacitances configured to be pre-charged to half the supply voltage.

12. The electro-optical modulator interface of claim 11, wherein said DC shifting stage further comprises back-to-back inverter latches configured to maintain a charge of said plurality of capacitances and maintain the two synchronous differential voltage drive signals in phase opposition.

13. A method of electro-optical interfacing using an electro-optical modulator interface comprising a two-branch output stage, each branch comprising a plurality of stacked CMOS inverter pairs, the method comprising:

driving, using the plurality of stacked CMOS inverter pairs of a given branch, a respective load capacitance coupled between an output of each of the plurality of stacked CMOS inverter pairs in phase opposition to the other branch; and

generating, using a pre-driver circuit coupled to the plurality of stacked CMOS inverter pairs, two synchronous differential voltage drive signals having a swing of half a supply voltage and being DC-shifted by half of the supply voltage with respect to each other.

14. The method of claim 13 wherein the pre-driver circuit comprises an input impedance matching stage, a DC shifting stage coupled to said input impedance matching stage, and a signal amplification core stage coupled to said input impedance matching stage.

15. The method of claim 14, further comprising pre-charging a plurality of capacitances of the DC shifting stage to half the supply voltage.

16. The method of claim 15, further comprising maintaining, using back-to-back inverter latches of the DC shifting stage, a charge of the plurality of capacitances and maintaining the two synchronous differential voltage drive signals in phase opposition.