# US 2019/0245501 A1 · Signal level detection and overrange signal limiter and clamp for electronic circuits > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2019/0245501 A1 - Document ID: US20190245501A1 - Status: Published application - Kind: A1 - Application number: 15/887,544 - Filed: 2018-02-02 - Published: 2019-08-08 - Earliest claimed: 2018-02-02 - Assignees: Analog Devices, Inc. - Applicants: Analog Devices, Inc. - Inventors: Huseyin DINC; Bryce GRAY; Ahmed Mohamed Abdelatty ALI - Web page: https://patentgrep.com/patent/US20190245501A1 ## CPC - H03G 3/30: in amplifiers having semiconductor devices - H03F 1/523: {for amplifiers using field-effect devices (H03F1/526 takes precedence)} - H03F 3/45183: {Long tailed pairs (H03F3/4521, H03F3/45237 take precedence)} - H03G 7/00: Volume compression or expansion in amplifiers {(frequency dependent H03G9/025)} - H03G 11/00: Limiting amplitude; Limiting rate of change of amplitude - H03F 2200/258: the input of the amplifier has voltage limiting means - H03F 2200/435: A peak detection being used in a signal measuring circuit in a controlling circuit of an amplifier - H03F 2200/441: Protection of an amplifier being implemented by clamping means - H03F 2200/78: A comparator being used in a controlling circuit of an amplifier - H03G: CONTROL OF AMPLIFICATION - H03F: AMPLIFIERS ## Abstract One embodiment is an apparatus including a detector circuit electrically coupled between a signal source and a second circuit, the signal source generating a first signal, the detector circuit detecting a level of the first signal and generating a first control signal when the detected level of the first signal exceeds a first threshold value, and a clamping switch electrically coupled to receive the first control signal from the detector circuit, the clamping switch including a multi-terminal active device. The first control signal controls a state of the clamping switch such that the clamping switch clamps a level of a signal applied to the second circuit when the level of the first signal exceeds the first threshold value. ## Claims ### Claim 1 An apparatus comprising: a detector circuit electrically coupled to a signal source and a second circuit, the signal source generating a first signal, the detector circuit detecting a level of the first signal and generating a first control signal when the detected level of the first signal exceeds a first threshold value; and a clamping switch electrically coupled to receive the first control signal from the detector circuit, the clamping switch comprising a multi-terminal active device; wherein the first control signal controls a state of the clamping switch such that the clamping switch clamps a level of a signal applied to the second circuit when the level of the first signal exceeds the first threshold value. ### Claim 2 (depends on 1) The apparatus of claim 1, wherein the detector circuit comprises a peak detector circuit for detecting a peak value of the first signal, wherein the peak detector circuit comprises a first MOSFET device, a second MOSFET device coupled to the first MOSFET device, and a source follower coupled to the first and second MOSFET devices, the source follower comprising a third MOSFET device and a capacitor. ### Claim 3 (depends on 2) The apparatus of claim 2, wherein the detector circuit comprises a comparator for comparing the detected peak value of the first signal with the first threshold value and generating the control signal when the detected peak value of the first signal exceeds the first threshold value. ### Claim 4 (depends on 3) The apparatus of claim 3, wherein the comparator comprises an amplifier. ### Claim 5 (depends on 1) The apparatus of claim 1, wherein the multi-terminal active device exhibits a variable impedance between first and second terminals thereof and a value of the variable impedance is controlled by a third terminal thereof. ### Claim 6 (depends on 5) The apparatus of claim 5, wherein the first control signal is applied to the third terminal of the multi-terminal active device. ### Claim 7 (depends on 1) The apparatus of claim 1, wherein the clamping switch comprises at least one of a p-channel metal oxide semiconductor field effect transistor (“PMOSFET”), an n-channel MOSFET (“NMOSFET”), a complementary MOSFET (“CMOSFET”), and a bi-polar junction transistor (“BJT”). ### Claim 8 (depends on 1) The apparatus of claim 1, wherein bits corresponding to the first control signal are input to an Automatic Gain Control (“AGC”) system for adjusting a level of the first signal. ### Claim 9 (depends on 1) The apparatus of claim 1, wherein the detector circuit further generates a second control signal when the level of the first signal exceeds a second threshold value. ### Claim 10 (depends on 1) The apparatus of claim 1, wherein bits corresponding to the second control signal are input to an Automatic Gain Control (“AGC”) system for adjusting a level of the first signal. ### Claim 11 An apparatus comprising: a detector circuit electrically coupled between a signal source and a second circuit, the signal source generating a first signal, the detector circuit comparing the first signal with first and second threshold values and generating a control signal when the detected level of the first signal exceeds the first threshold value or falls below the second threshold value; and a clamping switch electrically coupled to receive the control signal from the detector circuit, the clamping switch comprising a multi-terminal active device; wherein the control signal controls a state of the clamping switch such that the clamping switch clamps a level of a signal applied to the second circuit when the detected level of the first signal exceeds the first threshold value or falls below the second threshold value. ### Claim 12 (depends on 11) The apparatus of claim 11, wherein the detector circuit comprises a pair of cross-coupled fast amplifiers. ### Claim 13 (depends on 12) The apparatus of claim 12, wherein a first one of the pair of cross-coupled fast amplifiers is configured to generate the control signal when the first signal exceeds the first threshold value. ### Claim 14 (depends on 12) The apparatus of claim 12, wherein a second one of the pair of cross-coupled fast amplifiers is configured to generate the control signal when the first signal falls below the second threshold value. ### Claim 15 (depends on 11) The apparatus of claim 11, wherein the multi-terminal active device exhibits a variable impedance between first and second terminals thereof and wherein a value of the variable impedance is controlled by the third terminal and wherein the control signal is applied to the third terminal of the multi-terminal active device. ### Claim 16 (depends on 11) The apparatus of claim 11, wherein the clamping switch comprises at least one of a p-channel metal oxide semiconductor field effect transistor (“PMOSFET”), an n-channel MOSFET (“NMOSFET”), a complementary MOSFET (“CMOSFET”), and a bi-polar junction transistor (“BJT”). ### Claim 17 (depends on 11) The apparatus of claim 11, wherein bits corresponding to the control signal are input to an Automatic Gain Control (“AGC”) system for adjusting a level of the first signal. ### Claim 18 A method comprising: comparing a level of a first signal generated by a signal source to a first threshold value; generating a first control signal if the level of the first signal exceeds the first threshold value; and using the first control signal to activate a clamping switch comprising a multi-terminal active device, wherein the first control signal is provided to a first terminal of the multi-terminal active device and controls a value of a variable impedance between second and third terminals of the multi-terminal active device; wherein activation of the clamping switch clamps a value of a signal applied to a circuit under protection (“CUP”) to approximately the first threshold value. ### Claim 19 (depends on 18) The method of claim 18 further comprising providing bits corresponding to the first control signal to an Automatic Gain Control (“AGC”) system for adjusting a level of the first signal. ### Claim 20 (depends on 18) The method of claim 18 further comprising: generating a second control signal when the level of the first signal exceeds a second threshold value; and providing bits corresponding to the second control signal to an Automatic Gain Control (“AGC”) system for adjusting a level of the first signal.