Analog Devices Inc v. Number 14 BV

Prosecution History analysis

Examiner Search analysis

Invalidity Framework analysis

Petition

Petition Analysis

## 1. Case Identification
- Case Number: [IPR2025-00550](https://ai-lab.exparte.com/case/ptab/IPR2025-00550)
- Patent #: [7973596](https://ai-lab.exparte.com/docs/ptab/IPR2025-00550/1001)
- Filed: January 30, 2025
- Petitioner(s): [Analog Devices, Inc.](https://ai-lab.exparte.com/party/analog-devices-inc)
- Patent Owner(s): [Number 14 B.V.](https://ai-lab.exparte.com/party/number-14-bv)
- Challenged Claims: 21 and 22

## 2. Patent Overview
- Title: Method of Operating a Chopper Stabilized First Amplifier
- Brief Description: The [’596](https://ai-lab.exparte.com/docs/ptab/IPR2025-00550/1001) patent discloses methods for operating amplifiers that use both chopper stabilization and auto-zeroing techniques to reduce input voltage offset errors. The challenged claims are directed to methods where the chopping and auto-zeroing functions operate at specific frequency ratios and duty cycles.

## 3. Grounds for Unpatentability
#### Ground 1: Claims 21 and 22 are obvious over Pertijs
  - **Prior Art Relied Upon:** U.S. Patent No. 7,834,685 to [Pertijs](https://ai-lab.exparte.com/case/ptab/IPR2025-00550/doc/1011) (“[Pertijs](https://ai-lab.exparte.com/case/ptab/IPR2025-00550/doc/1011)”).
  - **Core Argument for this Ground:** Petitioner argued that [Pertijs](https://ai-lab.exparte.com/case/ptab/IPR2025-00550/doc/1011), which was not considered during prosecution, teaches a "chopped auto-zeroed ping-pong amplifier" that renders all limitations of claims 21 and 22 obvious.
    - **Prior Art Mapping:** Petitioner asserted that [Pertijs](https://ai-lab.exparte.com/case/ptab/IPR2025-00550/doc/1011) discloses a method of operating a chopper-stabilized amplifier with auto-zeroing capability. The chopper stabilization operates at a "first frequency" (one full cycle over four steps in its timing diagram), and the auto-zeroing operates at a "second frequency" (two pulses over the same four steps). This meets the limitations of operating at first and second frequencies. [Pertijs](https://ai-lab.exparte.com/case/ptab/IPR2025-00550/doc/1011) expressly states that chopping is performed at half the auto-zeroing frequency, which Petitioner contended meets the limitations that the second frequency is twice the first and the ratio is two-to-one, as required by claims 21 and 22.
    - **Motivation to Modify & Expectation of Success:** For claim 21, Petitioner argued [Pertijs](https://ai-lab.exparte.com/case/ptab/IPR2025-00550/doc/1011)’s timing diagram inherently shows an auto-zeroing duty cycle of less than one-half, as the auto-zeroing phase for a given stage occurs during two of the four total steps. For claim 22, which requires a duty cycle of not more than one-quarter, Petitioner contended it would be obvious to modify [Pertijs](https://ai-lab.exparte.com/case/ptab/IPR2025-00550/doc/1011). [Pertijs](https://ai-lab.exparte.com/case/ptab/IPR2025-00550/doc/1011) explicitly teaches its two-stage architecture can be extended to an "arbitrary number of stages." A POSITA would extend this to a four-stage system to further reduce noise, a known benefit. Such a four-stage system would logically operate over eight steps, with each stage being in auto-zero mode for two of the eight steps. This configuration results in an auto-zeroing duty cycle of 2/8, or one-quarter, rendering the limitation obvious.

#### Ground 2: Claim 22 is obvious over Tang
  - **Prior Art Relied Upon:** U.S. Patent No. 6,476,671 to [Tang](https://ai-lab.exparte.com/case/ptab/IPR2025-00550/doc/1006) (“[Tang](https://ai-lab.exparte.com/case/ptab/IPR2025-00550/doc/1006)”).
  - **Core Argument for this Ground:** Petitioner argued that [Tang](https://ai-lab.exparte.com/case/ptab/IPR2025-00550/doc/1006), also not considered during prosecution, discloses every element of claim 22. [Tang](https://ai-lab.exparte.com/case/ptab/IPR2025-00550/doc/1006) describes a ping-pong amplifier employing both auto-zeroing and chopping to achieve low offset voltage.
    - **Prior Art Mapping:** Petitioner mapped [Tang](https://ai-lab.exparte.com/case/ptab/IPR2025-00550/doc/1006)’s disclosure to the limitations of claim 22. [Tang](https://ai-lab.exparte.com/case/ptab/IPR2025-00550/doc/1006)’s circuit includes multiple amplifiers and a switch network enabling both auto-zeroing and chopping. In one embodiment (Fig. 4e), [Tang](https://ai-lab.exparte.com/case/ptab/IPR2025-00550/doc/1006)’s timing diagram shows an eight-phase cycle (Φ1-Φ8). Within this cycle, the chopper stabilization for a given amplifier has two pulses, while the auto-zeroing has one pulse. This establishes a "first frequency" of 2/(Φ1-Φ8) and a "second frequency" of 1/(Φ1-Φ8), which Petitioner asserted meets the claim limitation that the ratio of the frequencies is two-to-one.
    - **Motivation to Modify & Expectation of Success:** To meet the duty cycle limitation of not more than one-quarter, Petitioner pointed to [Tang](https://ai-lab.exparte.com/case/ptab/IPR2025-00550/doc/1006)’s explicit teaching that auto-zeroing for an amplifier, described as occurring over four phases (e.g., Φ1-Φ4), can be modified to occur during a shorter period, such as "during Φ1 only or during Φ2 only." Petitioner argued it would be obvious for a POSITA to apply this teaching to [Tang](https://ai-lab.exparte.com/case/ptab/IPR2025-00550/doc/1006)'s eight-phase timing diagram. If the phases are of equal duration (a simplifying and obvious choice), performing auto-zeroing during only two of the eight phases (e.g., Φ1 and Φ2) would result in a duty cycle of 2/8, or one-quarter, thus rendering the limitation obvious.

## 4. Key Claim Construction Positions
- **"first frequency" (chopper) and "second frequency" (auto-zero):** Petitioner argued these terms are not explicitly defined in the [’596](https://ai-lab.exparte.com/docs/ptab/IPR2025-00550/1001) patent and should be construed based on the patent’s examples. The proposed construction is "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 is central to interpreting the timing diagrams in the prior art to establish the claimed frequency and ratio limitations.
- **"the ratio of the two frequencies being two to one":** For claim 22, 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 supported by different embodiments in the [’596](https://ai-lab.exparte.com/docs/ptab/IPR2025-00550/1001) patent specification.

## 5. Arguments Regarding Discretionary Denial
- Petitioner argued that discretionary denial is not warranted.
- **Denial under *Fintiv*:** Petitioner contended the *Fintiv* factors do not apply because the co-pending district court case is a licensing dispute, not a patent infringement action. Therefore, no parallel validity analysis is occurring, and there is no risk of duplicative efforts or inconsistent rulings.
- **Denial under §325(d):** Petitioner asserted that denial under §325(d) is improper because the primary references, [Pertijs](https://ai-lab.exparte.com/case/ptab/IPR2025-00550/doc/1011) and [Tang](https://ai-lab.exparte.com/case/ptab/IPR2025-00550/doc/1006), were not before the Examiner during the original prosecution. Furthermore, the arguments presented in the petition based on this new art are substantially different from those previously considered by the USPTO.

## 6. Relief Requested
- Petitioner requested institution of an inter partes review and cancellation of claims 21 and 22 of the [’596](https://ai-lab.exparte.com/docs/ptab/IPR2025-00550/1001) patent as unpatentable under 35 U.S.C. §103.

Analog Devices targets chopper amplifier patent with new prior art: Pertijs & Tang cited for obviousness of claims 21-22 on frequency/duty cycle.