# US 2013/0154726 A1 · Second order active high-pass filter with cross-coupled feedback for q enhancement > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2013/0154726 A1 - Document ID: US20130154726A1 - Status: Published application - Kind: A1 - Application number: 13/326,557 - Filed: 2011-12-15 - Published: 2013-06-20 - Earliest claimed: 2011-12-15 - Assignees: LSI Corporation - Inventors: Andrew P. Krebs - Web page: https://patentgrep.com/patent/US20130154726A1 ## CPC - H03H 11/0422: {using transconductance amplifiers, e.g. gmC filters} - H03F 3/4508: {using bipolar transistors as the active amplifying circuit (H03F3/45278 takes precedence)} - H03H 11/0461: {Current mode filters} - H03H 11/0472: {Current or voltage controlled filters} - H03H 11/1291: {Current or voltage controlled filters} - H03F 2203/45318: the AAC comprising a cross coupling circuit, e.g. two extra transistors cross coupled - H03H: IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS (waveguides, resonators, lines or other devices of the waveguide type H01P) - H03F: AMPLIFIERS ## Abstract An apparatus comprising an input circuit, a cross coupled active circuit and an output circuit. The input circuit may be configured to generate a first portion of an intermediate signal in response to an input signal. The cross coupled active circuit may be configured to generate a second portion of the intermediate signal in response to a feedback of an output signal. The output circuit may be configured to generate the output signal in response to the intermediate signal. The output signal may pass frequencies above a target frequency. ## Claims ### Claim 1 An apparatus comprising: an input circuit configured to generate a first portion of an intermediate signal in response to an input signal; a cross coupled active circuit configured to generate a second portion of said intermediate signal in response to a feedback of an output signal; and an output circuit configured to generate said output signal in response to said intermediate signal, wherein said output signal passes frequencies above a target frequency. ### Claim 2 (depends on 1) The apparatus according to claim 1, wherein said input signal comprises a differential input signal and said output signal comprises a differential output signal. ### Claim 3 (depends on 1) The apparatus according to claim 1, wherein said apparatus is implemented as one or more integrated circuits. ### Claim 4 (depends on 1) The apparatus according to claim 1, wherein: said output circuit comprises a first transistor configured to receive a bias signal, a first capacitor, a second transistor configured to receive said bias signal, and a second capacitor. ### Claim 5 (depends on 4) The apparatus according to claim 4, wherein said target frequency is set by adjusting a value Gm of said first and second transistors. ### Claim 6 (depends on 5) The apparatus according to claim 5, wherein said input circuit comprises a third transistor, a third capacitor, a fourth transistor and a fourth capacitor. ### Claim 7 (depends on 6) The apparatus according to claim 6, wherein said target frequency is set by adjusting a value Gm of said third and fourth transistors. ### Claim 8 (depends on 1) The apparatus according to claim 1, wherein said cross-coupled active circuit comprises a first cross coupled transistor and a second cross coupled transistor. ### Claim 9 (depends on 1) The apparatus according to claim 1, wherein said apparatus further comprises: an adjustment circuit configured to set said target frequency. ### Claim 10 (depends on 9) The apparatus according to claim 9, wherein said adjustment circuit comprises a first current source, a second current source and a third current source each connected to a DC voltage. ### Claim 11 (depends on 10) The apparatus according to claim 10, wherein said target frequency is set by changing values of said first current source, said second current source and said third current source. ### Claim 12 (depends on 1) The apparatus according to claim 1, wherein said apparatus comprises a second order high-pass filter. ### Claim 13 (depends on 1) The apparatus according to claim 1, wherein said apparatus generates a roll-off of nearly 40 dB/dec. ### Claim 14 (depends on 1) The apparatus according to claim 1, wherein said apparatus comprises a second order active high-pass filter with cross-coupled feedback for Q enhancement. ### Claim 15 A method for implementing a high pass filter, comprising the steps of: (A) generating a first portion of an intermediate signal in response to an input signal; (B) generating a second portion of said intermediate signal in response to a feedback of an output signal; and (C) generating said output signal in response to said intermediate signal, wherein said output signal passes frequencies above a target frequency. ### Claim 16 (depends on 15) The apparatus according to claim 15, wherein said input signal comprises a differential input signal and said output signal comprises a differential output signal. ### Claim 17 (depends on 15) The apparatus according to claim 15, wherein said target frequency is set by adjusting a value Gm. ### Claim 18 (depends on 15) The apparatus according to claim 15, wherein said target frequency is set by changing values of a first current source, a second current source and a third current source. ### Claim 19 (depends on 15) The apparatus according to claim 15, wherein said apparatus generates a roll-off of nearly 40 dB/dec. ### Claim 20 An apparatus comprising: means for generating a first portion of an intermediate signal in response to an input signal; means for generating a second portion of said intermediate signal in response to a feedback of an output signal; and means for generating said output signal in response to said intermediate signal, wherein said output signal passes frequencies above a target frequency.