PTAB

IPR2025-00551

Analog Devices Inc v. Number 14 BV

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Petition
petition

1. Case Identification

2. Patent Overview

  • Title: Amplifier System with Power on Calibration
  • Brief Description: The ’665 patent discloses an apparatus for power-on calibration (auto-zeroing) of the input offset voltage of an amplifier. The system uses a successive approximation register (SAR) and a digital-to-analog converter (DAC) to determine and apply an offset correction voltage.

3. Grounds for Unpatentability

Ground 1: Obviousness over Krum and Munoz - Claims 1-4 and 9 are obvious over Krum in view of Munoz.

  • Prior Art Relied Upon: Krum (F. Krummenacher et al., a 1997 IEEE article) and Munoz (Patent 6,486,806).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Krum discloses a CMOS operational amplifier (opamp) with an auto-zeroing circuit that is structurally and functionally similar to the system claimed in the ’665 patent. Krum’s system includes an amplifier, comparator, SAR, switches, and a DAC (termed CALDAC) for offset compensation. Petitioner contended that the only significant element of independent claim 1 not taught by Krum is a DAC being a "non-binary converter using a radix of less than 2." Munoz was asserted to remedy this deficiency by explicitly teaching a SAR DAC system designed with a radix of less than two to overcome the "binary non-overlap problem," improve accuracy, and provide redundancy.
    • Motivation to Combine: A Person of Ordinary Skill in the Art (POSITA) would combine Krum and Munoz to improve Krum's system. Krum's DAC requires monotonicity but provides few implementation details. A POSITA seeking to implement Krum would look to references like Munoz, which provides a detailed, monotonic DAC. Furthermore, Munoz’s use of a radix less than two addresses the well-known problem of gaps in DAC output and allows for recovery from noise-induced errors, providing clear reasons to incorporate its teachings into Krum's offset calibration circuit.
    • Expectation of Success: Petitioner argued there would be a reasonable expectation of success. The combination involves substituting one known type of DAC (Munoz) for another (in Krum) to gain a predictable improvement in performance. Munoz’s DAC is described in relation to various DAC types and could be used to replace Krum’s current-mode DAC with routine engineering.

Ground 2: Obviousness over Krum, Munoz, and Yan - Claims 1 and 5-7 are obvious over Krum and Munoz in view of Yan.

  • Prior Art Relied Upon: Krum (1997 IEEE article), Munoz (Patent 6,486,806), and Yan (Patent 7,642,846).
  • Core Argument for this Ground:
    • Prior Art Mapping: This ground builds upon the Krum and Munoz combination from Ground 1. Petitioner argued that a POSITA could choose to implement the Munoz DAC as a voltage-mode DAC instead of a current-mode DAC. Doing so in Krum’s system would require an additional transconductance stage to convert the DAC’s voltage output into a current suitable for offset cancellation. Yan was asserted to disclose just such a transconductance stage for use in opamp offset compensation circuitry. The combination thus teaches all limitations of the challenged claims, including the transconductance differential input stages recited in claim 5.
    • Motivation to Combine: The motivation to combine Krum and Munoz is the same as in Ground 1. A POSITA, having decided to use a voltage-mode DAC (a known design choice), would predictably turn to prior art like Yan to find a standard transconductance stage to integrate the components. Yan falls within the same field of endeavor—opamps with offset compensation—making it a natural source for a POSITA to consult. The combination represents the predictable use of prior art elements according to their established functions.
    • Expectation of Success: Implementation would be well within the skill of a POSITA and yield predictable results. Each element—the Krum amplifier, the Munoz DAC, and the Yan transconductance stage—has an established function that it would perform in the proposed combination.

Ground 3: Obviousness over Wang, Weir, and Ferguson - Claims 1-4 and 9 are obvious over Wang in view of Weir and Ferguson.

  • Prior Art Relied Upon: Wang (Patent 7,265,611), Weir (Patent 4,336,526), and Ferguson (Patent 5,789,974).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner asserted that Wang teaches a base amplifier system with self-zeroing circuitry, including a comparator, SAR, and DAC. However, Wang does not teach a non-binary DAC. Weir was argued to address this by disclosing a successive approximation converter that employs a non-binary sequence (radix < 2) to reduce the strict accuracy requirements of the DAC components. Ferguson was argued to teach adding switches and a "catching amplifier" to an offset calibration system to reduce unwanted voltage glitches at the output when the amplifier is muted for calibration.
    • Motivation to Combine: A POSITA would be motivated to improve Wang’s system in two ways. First, a POSITA would replace Wang’s standard DAC with the improved non-binary DAC from Weir to increase the precision and robustness of the offset compensation, a primary goal of Wang. Second, a POSITA would incorporate Ferguson’s anti-glitch switching circuitry to improve the quality of Wang's system output, preventing unwanted glitches during the calibration process.
    • Expectation of Success: The proposed combination would be a predictable result of routine engineering. It involves substituting a known, improved component (Weir's DAC) and adding a known improvement circuit (Ferguson's switches) into a base system (Wang) to achieve their respective, well-understood benefits.

4. Key Claim Construction Positions

  • “non-binary converter using a radix of less than 2 for at least the most significant bits” [claim 1]: Petitioner proposed this term be construed as requiring the element ratio between bit N and bit (N-1), and the ratio between bit (N-1) and bit (N-2), to each be lower than 2, where N is the Most Significant Bit (MSB). This construction was central to mapping Munoz and Weir to the claims.
  • “coupled” / “being coupled” [claims 1, 5, 6, 7, 8]: Petitioner proposed this term be understood to mean connecting directly or indirectly through one or more intervening devices.

5. Arguments Regarding Discretionary Denial

  • Petitioner argued against discretionary denial under Fintiv because the only co-pending district court case is not a patent infringement action, meaning no other court is analyzing the validity of the ’665 patent.
  • Petitioner argued against denial under 35 U.S.C. §325(d). Although Krum was cited in an Information Disclosure Statement (IDS), it was never applied in a rejection, and Petitioner contended the examiner erred by overlooking Krum's clear teachings. The other primary references (Munoz, Yan, Wang, Weir, Ferguson) were not before the examiner, meaning the asserted grounds are not the same or substantially the same as arguments previously presented.

6. Relief Requested

  • Petitioner requests institution of inter partes review and cancellation of claims 1-7 and 9 of Patent 7,812,665 as unpatentable.