# US 11,451,202 B2 · Signal output circuit > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,451,202 B2 - Document ID: US11451202B2 - Status: Granted - Kind: B2 - Application number: 17/130,011 - Filed: 2020-12-22 - Published: 2021-04-15 - Granted: 2022-09-20 - Earliest claimed: 2018-07-12 - Assignees: Denso Corporation - Applicants: Denso Corporation - Inventors: Takahisa Koyasu - Web page: https://patentgrep.com/patent/US11451202B2 ## CPC - H03F 3/343: with semiconductor devices only - H03F 3/45179: {using MOSFET transistors as the active amplifying circuit (H03F3/45278 takes precedence)} - H03F 1/34: Negative-feedback-circuit arrangements with or without positive feedback (H03F1/02 - H03F1/30, H03F1/38 - H03F1/50, H03F3/50 take precedence {; for rejection of common mode signals H03F3/45479}) - H03F 3/245: {with semiconductor devices only} - H03F 3/72: Gated amplifiers, i.e. amplifiers which are rendered operative or inoperative by means of a control signal - H03K 17/16: Modifications for eliminating interference voltages or currents - H03F 1/52: Circuit arrangements for protecting such amplifiers {(monitoring arrangements G01R31/28; increasing reliability in communication systems, e.g. using redundancy H04B1/74)} - H03F 2200/141: the feedback circuit of the amplifier stage comprising a resistor and a capacitor in series, at least one of them being an active one - H03F 2200/171: A filter circuit coupled to the output of an amplifier - H03F 2200/33: Bridge form coupled amplifiers; H-form coupled amplifiers - H03F 2200/441: Protection of an amplifier being implemented by clamping means - H03F: AMPLIFIERS - H03K: PULSE TECHNIQUE (measuring pulse characteristics G01R; modulating sinusoidal oscillations with pulses H03C; transmission of digital information H04L; discriminator circuits detecting phase difference between two signals by counting or integrating cycles of oscillation H03D3/04; automatic control, starting, synchronisation or stabilisation of generators of electronic oscillations or pulses where the type of generator is irrelevant or unspecified H03L; coding, decoding or code conversion, in general H03M) ## Abstract A signal output circuit includes an inverting amplifier circuit, a feedback capacitor and a low pass filter. The inverting amplifier circuit includes an input terminal and an output terminal. The inverting amplifier circuit executes an inverting amplification based on an input signal to output a signal to the output terminal at a pull-up state. An output stage of the inverting amplifier circuit is an open collector or an open drain. The feedback capacitor is connected between the input terminal and the output terminal of the inverting amplifier circuit. The low pass filter has an input and an output. The input of the low pass filter is connected to the output terminal of the inverting amplifier. The output of the low pass filter is connected to the feedback capacitor. ## Claims ### Claim 1 A signal output circuit comprising: an inverting amplifier circuit including an input terminal and an output terminal, the inverting amplifier circuit configured to execute an inverting amplification operation based on an input signal to output a signal to the output terminal at a pull-up state, the inverting amplifier circuit having an output stage being either an open collector or an open drain; a feedback capacitor connected between the input terminal and the output terminal of the inverting amplifier circuit; a low pass filter circuit having an input and an output, the input being connected to the output terminal of the inverting amplifier, the output being connected to the feedback capacitor; an output transistor connected between the output terminal of the inverting amplifier circuit and a ground; a charge/discharge circuit connected to the input terminal of the inverting amplifier circuit, the charge/discharge circuit configured to charge the feedback capacitor in response to that the input signal is changed to a high level from a low level, and discharge the feedback capacitor in response to that the input signal is changed to the low level from the high level; and a clamping transistor connected between a conductive control terminal of the output transistor and the ground, wherein a conductive control terminal of the clamping transistor is connected to a connection terminal of the feedback capacitor and a connection terminal of the charge/discharge circuit, and wherein the clamping transistor conducts in response to that noise is applied to the conductive control terminal of the output transistor, in a situation where the feedback capacitor is discharged. ### Claim 2 (depends on 1) The signal output circuit according to claim 1, further comprising: a capacitor connected to the clamping transistor in parallel. ### Claim 3 (depends on 1) The signal output circuit according to claim 1, further comprising: a bridge circuit having a first series circuit and a second series circuit connected in parallel, each of the first series circuit and the second series circuit having two diodes connected in a forward direction, the bridge circuit having an anode side located on a downstream side in the forward direction and a cathode side located on an upstream side in the forward direction, wherein the anode side of the bridge circuit is connected to a resistive element, which pulls up the output terminal wherein the output transistor is connected between the ground and the cathode side of the bridge circuit, wherein the first series circuit has a common connection node connected to the output terminal, and the second series circuit has a common connection node connected to the feedback capacitor. ### Claim 4 (depends on 3) The signal output circuit according to claim 3, wherein the low pass filter circuit includes a first low pass filter and a second low pass filter, wherein the first low pass filter is disposed at the anode side of the bridge circuit facing the resistive element, and the second low pass filter is disposed at the cathode side of the bridge circuit facing the output transistor. ### Claim 5 (depends on 1) The signal output circuit according to claim 1, further comprising: a phase compensating resistive element connected to the feedback capacitor in series, wherein the low pass filter circuit is connected between the output terminal and the phase compensating resistive element. ### Claim 6 (depends on 1) The signal output circuit according to claim 1, wherein the low pass filter circuit is a CR filter. ### Claim 7 (depends on 1) The signal output circuit according to claim 1, wherein the low pass filter circuit is a voltage follower including an operational amplifier. ### Claim 8 (depends on 3) The signal output circuit according to claim 3, wherein the common connection node in the first series circuit is between the two diodes in the first series circuit, and wherein the common connection node in the second series circuit is between the two diodes in the second series circuit.