DCT
1:11-cv-01073
Signal Tech LLC v. Analog Devices Inc
I. Executive Summary and Procedural Information
- Parties & Counsel:
- Plaintiff: Signal Tech, LLC (Delaware)
- Defendant: Analog Devices, Inc. (Massachusetts)
- Plaintiff’s Counsel: Farnan LLP
- Case Identification: 1:11-cv-01073, D. Del., 11/02/2011
- Venue Allegations: Plaintiff alleges venue is proper in the District of Delaware because Defendant has established minimum contacts with the state, places products into the stream of commerce with the knowledge they will be sold in Delaware, and has committed tortious acts of patent infringement in the state.
- Core Dispute: Plaintiff alleges that Defendant’s amplifier products infringe a patent related to a method and apparatus for an efficient, low-voltage switchable transconductance (Gm) cell.
- Technical Context: The technology concerns the design of tunable transconductance (Gm) cells, which are fundamental building blocks in analog integrated circuits such as filters and amplifiers used in communications and data storage applications.
- Key Procedural History: The complaint does not mention any prior litigation, post-grant proceedings, or licensing history related to the patent-in-suit.
Case Timeline
| Date | Event |
|---|---|
| 2001-05-25 | ’064 Patent Priority Date |
| 2002-11-12 | U.S. Patent No. 6,480,064 Issues |
| 2011-11-02 | Complaint Filed |
II. Technology and Patent(s)-in-Suit Analysis
U.S. Patent No. 6,480,064 - “Method and Apparatus for an Efficient Low Voltage Switchable Gm Cell”
- Patent Identification: U.S. Patent No. 6480064, “Method and Apparatus for an Efficient Low Voltage Switchable Gm Cell,” issued November 12, 2002 (’064 Patent).
The Invention Explained
- Problem Addressed: The patent addresses the challenge of designing tunable transconductance (Gm) cells for analog circuits that must operate over a wide tuning range while using a low power-supply voltage (’064 Patent, col. 1:16-19). Prior art approaches required wide-ranging tuning voltages, which could cause poor distortion, or used multiple tuning voltages, which created design complexity from overlapping operational ranges (’064 Patent, col. 1:40-51).
- The Patented Solution: The invention proposes a “switchable Gm cell” that includes a plurality of “Gm setting devices” (e.g., transistors) and a “switching circuit” (’064 Patent, Abstract). The switching circuit receives a digital “Gm setting code” to selectively turn individual Gm setting devices on or off, allowing for large, discrete “coarse” adjustments to the circuit’s overall transconductance. A separate, conventional analog “tuning voltage” can then be used for small “fine” adjustments, but within a much narrower and more manageable voltage range (’064 Patent, col. 2:1-13; col. 5:52-64). This architecture is illustrated in the embodiments shown in Figures 1 and 2.
- Technical Importance: This design allows for the creation of high-performance, dynamically adjustable analog circuits that are compatible with the low operating voltages of modern semiconductor technologies (’064 Patent, col. 1:21-26).
Key Claims at a Glance
- The complaint alleges infringement of one or more claims without specifying which ones (Compl. ¶12). Independent claim 1 is representative of the core invention.
- Independent Claim 1:
- A switching Gm cell comprising:
- a plurality of Gm setting devices, each of said Gm setting devices comprising at least one transistor;
- a switching circuit connected with said Gm setting devices and operable to receive a Gm setting code and provide a voltage to said Gm setting devices.
- The complaint’s general allegation of infringement of “one or more claims” preserves the right to assert dependent claims later in the litigation (Compl. ¶12).
III. The Accused Instrumentality
- Product Identification: The complaint identifies the accused instrumentalities as the AD830 amplifier, the AD8370 amplifier, and the "Zero-Drift Operational Amplifiers" (Compl. ¶13).
- Functionality and Market Context: The complaint identifies the accused products as amplifiers but does not provide any specific details about their internal architecture, relevant features, or how they operate (Compl. ¶13). No allegations are made regarding the products' specific commercial importance beyond their general sale by the Defendant. No probative visual evidence provided in complaint.
IV. Analysis of Infringement Allegations
The complaint does not provide a claim chart or detailed infringement theory. It asserts that the accused products infringe by being devices that embody the patented invention (Compl. ¶¶12-13). The complaint’s primary factual allegation connecting the patent to the products is its high-level description that the patent claims "a device that contains multiple Gm setting devices and a switching circuit connected to the Gm setting devices" (Compl. ¶9). The infringement analysis below is based on this general allegation against the elements of independent claim 1.
’064 Patent Infringement Allegations
| Claim Element (from Independent Claim 1) | Alleged Infringing Functionality | Complaint Citation | Patent Citation |
|---|---|---|---|
| a plurality of Gm setting devices, each of said Gm setting devices comprising at least one transistor | The complaint alleges that the accused products, including the AD830 and AD8370 amplifiers, are infringing devices that contain the claimed elements. | ¶¶9, 13 | col. 5:55-60 |
| a switching circuit connected with said Gm setting devices and operable to receive a Gm setting code and provide a voltage to said Gm setting devices | The complaint alleges that the accused products, as infringing devices, contain a switching circuit connected to the Gm setting devices as claimed in the patent. | ¶¶9, 13 | col. 5:61-64 |
- Identified Points of Contention:
- Architectural Questions: A central question will be whether the accused amplifiers contain a circuit architecture that maps onto the claim elements. The case will depend on evidence showing whether the products actually contain a "plurality of Gm setting devices" that are controlled by a distinct "switching circuit" receiving a "Gm setting code."
- Technical Questions: The complaint provides no information on how the accused amplifiers achieve tunable transconductance. A key technical dispute will be whether their internal method of adjustment is functionally the same as the digitally-switched coarse/fine adjustment method described and claimed in the ’064 Patent, or if they employ a different, non-infringing technique.
V. Key Claim Terms for Construction
The complaint does not provide sufficient detail for a definitive analysis of claim construction disputes. However, based on the patent's description of the invention, the following terms are likely to be central to the case.
The Term: "switching circuit"
Context and Importance: This term is the functional heart of the invention, distinguishing it from prior art that used wide-range analog tuning voltages. The entire infringement case rests on whether the accused products contain a structure that meets the definition of a "switching circuit." Practitioners may focus on this term because its scope will determine whether only specific digital decoder embodiments are covered or if a broader range of selection logic infringes.
Intrinsic Evidence for Interpretation:
- Evidence for a Broader Interpretation: Claim 1 itself provides a functional definition: a circuit "operable to receive a Gm setting code and provide a voltage to said Gm setting devices" (’064 Patent, col. 6:1-3). This broad functional language may support an interpretation that covers any circuit performing this role, regardless of its specific implementation.
- Evidence for a Narrower Interpretation: The specification describes specific preferred embodiments, such as the switching circuit 500 in FIG. 5, which includes a "digital decoder 520" and a multiplexer-like arrangement of transistors (’064 Patent, col. 5:1-11). A defendant may argue that the term should be limited to these more complex, digitally-decoded structures.
The Term: "Gm setting code"
Context and Importance: This term defines the input that controls the "switching circuit" for coarse adjustments. The nature of this "code"—whether it must be digital, and what form it must take—is critical for determining infringement.
Intrinsic Evidence for Interpretation:
- Evidence for a Broader Interpretation: The term "code" is not explicitly defined. Plaintiff may argue it should be given its plain and ordinary meaning, which could encompass any set of electrical signals—analog or digital—that convey selection information.
- Evidence for a Narrower Interpretation: The specification consistently describes the "Gm setting code" in the context of digital schemes, such as "thermometer-coded," "binary coded," and "segmented thermometer coded" arrangements (’064 Patent, col. 4:30-64). The patent also describes a "digital decoder" for processing the code, further suggesting a digital nature (’064 Patent, col. 3:59-62).
VI. Other Allegations
- Willful Infringement: The complaint does not use the term "willful." However, it alleges that Defendant's infringement is "exceptional and entitles Signal Tech, LLC to attorneys' fees and costs" under 35 U.S.C. § 285 (Compl. ¶14). The complaint does not plead any specific facts to support this allegation, such as pre-suit knowledge of the patent.
VII. Analyst’s Conclusion: Key Questions for the Case
- A primary issue will be one of architectural evidence: As the complaint lacks any technical detail about the accused products, the case will turn on whether discovery reveals that the internal circuitry of Defendant’s amplifiers practices the claimed combination of a "plurality of Gm setting devices" controlled by a "switching circuit" that operates on a "Gm setting code."
- The outcome will also hinge on a question of definitional scope during claim construction: Will the court construe the term "switching circuit" broadly based on its functional description in the claim, or will it be narrowed to the specific digital decoder-based embodiments described in the specification? The resolution of this question will likely define the boundaries of infringement.