Apple patents filter circuit that cleans up audio signals
Apple has filed a patent for a specific type of electronic filter circuit used in signal processing. The design combines an active filter to remove high-frequency noise with a passive switched-capacitor filter that uses feedback to shape the signal's frequency response. A buffer circuit then stabilizes the output to drive other components.
In the filing’s own words
A filter circuit that employs both an active filter circuit and a switched-capacitor filter circuit is disclosed. The active filter circuit may suppress high-frequency blocker signals near a sampling frequency of the switched-capacitor filter circuit to generate a pre-filtered signal. The switched-capacitor filter circuit may employ feedback to introduce a complex pole into the transfer circuit of the filter circuit. A load-driver circuit may be used to buffer the output of the switched-capacitor filter circuit in order to drive a desired load circuit.
What exactly they claim (claim 1)
1. An apparatus, comprising: a pre-filter circuit configured to filter an input signal to generate a pre-filtered signal; a switched-capacitor filter circuit configured to: couple the pre-filtered signal to a first filter node during a first time period, wherein the first filter node is coupled to a ground supply node via a first capacitor; couple a second capacitor between the first filter node and a ground supply node during a second time period subsequent to the first time period; couple an output signal to the first filter node via a third capacitor during the second time period; and couple a fourth capacitor between the first filter node and the ground supply node during a third time period subsequent to the second time period; and a buffer circuit configured to generate the output signal using a voltage level across the fourth capacitor.
Facts
- Company
- Apple (Apple Inc.)
- Official title
- PASSIVE SWITCHED-CAPACITOR FILTER WITH TUNABLE COMPLEX POLES
- Publication number
- US20260312567A1
- Application number
- 19098838
- Filed
- Apr 2, 2025
- Published
- Oct 8, 2026
- Inventors
- 4
- Claims
- 20
Classified under
H03H 11/12 Electricity & electronicsMore from Apple in Chips & hardware
- Apple patents glass chip base that uses light to move data Oct 8, 2026
- Apple patents radar that maps rooms using moving objects Sep 1, 2026
- Apple patents display method that reuses static images to save power Sep 1, 2026
- Apple patents stretchable OLED displays with sealed pixel islands Sep 8, 2026
- Apple patents method to fix color fringes in high-resolution displays Sep 8, 2026
Summaries are simplified from the filing’s own abstract and first claim. A patent filing is not a product announcement.
Patent data and drawings: U.S. Patent and Trademark Office (USPTO). Nebula is not affiliated with or endorsed by the USPTO.