Analog Devices Inc v. Number 14 BV

1. Case Identification

• Case #: IPR2025-00550
• Patent #: 7,973,596
• Filed: January 30, 2025
• Petitioner(s): Analog Devices, Inc.
• Patent Owner(s): Number 14 B.V.
• Challenged Claims: 21-22

2. Patent Overview

• Title: Method of Operating a Chopper Stabilized Amplifier
• Brief Description: The ’596 patent relates to methods for operating chopper stabilized amplifiers that also possess an auto-zeroing capability. The technology aims to counteract input voltage offsets and other imperfections in operational amplifiers by combining these two known offset-reduction techniques with specific frequency and duty cycle relationships.

3. Grounds for Unpatentability

Ground 1: Obviousness over Pertijs - Claims 21-22 are obvious over Pertijs

• Prior Art Relied Upon: Pertijs (Patent 7,834,685).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that Pertijs, which was not considered during prosecution, discloses all limitations of the challenged claims. Pertijs describes a "chopped auto-zeroed ping-pong amplifier" that operates using a four-step timing cycle. Petitioner asserted that analysis of Pertijs’s timing diagrams (Fig. 2) shows chopper stabilization operating at a first frequency (one cycle over the four steps) and auto-zeroing operating at a second frequency (two pulses over the four steps). This results in the second (auto-zeroing) frequency being twice the first (chopping) frequency, meeting the ratio limitations of claims 21 and 22. For claim 21, Petitioner contended the auto-zeroing duty cycle is less than one half because it occurs during two of the four steps. For claim 22, Petitioner argued it would have been obvious to a POSITA to extend Pertijs's explicitly scalable two-stage architecture to four stages. In such a configuration, each stage would be auto-zeroed for two of the total eight steps, resulting in a duty cycle of not more than one-quarter.
  • Motivation to Combine (for §103 grounds): As this is a single-reference ground, no motivation to combine was required. Petitioner argued Pertijs itself renders the claims obvious.
  • Expectation of Success (for §103 grounds): Petitioner contended that extending Pertijs’s architecture to four stages was a simple, predictable design modification explicitly suggested by Pertijs to improve noise performance.

Ground 2: Obviousness over Tang - Claim 22 is obvious over Tang

• Prior Art Relied Upon: Tang (Patent 6,476,671).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that Tang, also not before the Examiner, discloses a ping-pong amplifier that employs both auto-zeroing and chopping techniques. In an embodiment with an eight-phase timing cycle (Fig. 4e), Tang performs two chopper stabilization cycles for each auto-zero period, explicitly meeting the limitation that the chopping frequency is twice the auto-zeroing frequency (and thus the ratio is two-to-one). To meet the duty cycle limitation of claim 22, Petitioner pointed to Tang’s teaching that auto-zeroing, described as occurring over two phases (e.g., Φ1 and Φ2), could be performed during only one phase (e.g., Φ1 only). Petitioner asserted it would be obvious to apply this shortened duty cycle to the eight-phase timing arrangement. This modification would result in an auto-zeroing duty cycle of 1/8, which is "not more than one quarter."
  • Motivation to Combine (for §103 grounds): This is a single-reference ground. The argument relied on combining different teachings within Tang. A POSITA would have been motivated to apply the shortened duty cycle teaching to the eight-phase embodiment to simplify the timing mechanism, a predictable design choice.
  • Expectation of Success (for §103 grounds): Petitioner argued a POSITA would have had a high expectation of success, as Tang itself states that performing auto-zeroing over one phase instead of two is "functionally equivalent."

4. Key Claim Construction Positions

• "first frequency" and "second frequency": Petitioner proposed these terms be construed based on their use in the ’596 patent’s specification and figures. The "first frequency" (chopper stabilization) and "second frequency" (auto-zeroing) should be defined as "the number of active pulses of a [chopper/auto-zeroing] switch in a full cycle period divided by the period of the cycle." This construction was central to calculating the frequencies, ratios, and duty cycles from the prior art timing diagrams.
• "the ratio of the two frequencies being two to one": Petitioner argued this term should be construed to mean that either the auto-zero frequency is twice the chopper frequency or the chopper frequency is twice the auto-zero frequency. This interpretation is consistent with different embodiments shown in the ’596 patent.

5. Arguments Regarding Discretionary Denial

• Discretionary Denial under Fintiv: Petitioner argued against discretionary denial because the only co-pending district court case is a licensing dispute, not a patent infringement action. Therefore, the validity of the ’596 patent is not at issue in that proceeding, and there is no risk of duplicative efforts or inconsistent rulings on validity.
• Discretionary Denial under §325(d): Petitioner contended denial would be improper because the core prior art references, Pertijs and Tang, are highly material and were not before the Examiner during the original prosecution. The arguments presented in the petition were therefore not previously considered by the USPTO.

6. Relief Requested

• Petitioner requests institution of inter partes review and cancellation of claims 21-22 of Patent 7,973,596 as unpatentable.