초록 ▼

A Schmitt trigger circuit that has a separate HI bias circuit, a separate LO bias circuit, and a trigger circuit that includes HI and LO sections that respectively match the circuitry in the HI and LO bias circuits. HI and LO threshold signals are applied to locations in the HI and LO bias circuits

A Schmitt trigger circuit that has a separate HI bias circuit, a separate LO bias circuit, and a trigger circuit that includes HI and LO sections that respectively match the circuitry in the HI and LO bias circuits. HI and LO threshold signals are applied to locations in the HI and LO bias circuits that correspond to an input terminal for the trigger circuit, while particular nodes in the bias circuits are connected to corresponding locations in the trigger circuit to set up matching signal levels when the trigger input equals either the HI or the LO threshold levels. The bias circuits include negative feedback paths which inhibit errors due to process, temperature or supply voltage variations, while switching set points are applied to the bias circuits and reflected to the trigger circuit to set the output voltage at a desired level that corresponds to an intermediate point in the switching transition. The circuit can thus be set to be at the middle of a switching transition, with a maximum rate of output voltage change, at the threshold levels.

대표청구항 ▼

A Schmitt trigger circuit, comprising: means for establishing HI and LO threshold voltages, a HI bias circuit having operative circuitry that is responsive to said HI threshold voltage for establishing a HI bias signal, a LO bias circuit having operative circuitry that is responsive to said LO thres

A Schmitt trigger circuit, comprising: means for establishing HI and LO threshold voltages, a HI bias circuit having operative circuitry that is responsive to said HI threshold voltage for establishing a HI bias signal, a LO bias circuit having operative circuitry that is responsive to said LO threshold voltage for establishing a LO bias signal, and a trigger circuit that is connected to receive an input signal, said trigger circuit including: a HI section that substantially matches the operative circuitry of said HI bias circuit, and is biased by said HI bias signal to switch from a LO to a HI trigger circuit output in response to said input signal rising from a level below said LO threshold voltage to a level above said HI threshold voltage, and a LO section that substantially matches the operative circuitry of said LO bias circuit, and is biased by said LO bias signal to switch from a HI to a LO trigger circuit output in response to said input signal falling from a level above said HI threshold voltage to a level below said LO threshold voltage, corresponding nodes in the matching circuitry of said HI bias circuit and said HI trigger circuit section being connected together to bias said HI trigger circuit section, and corresponding nodes in the matching circuitry of said LO bias circuit and said LO trigger circuit section being connected together to bias said LO trigger circuit section, the operative circuitry of said HI bias circuit including: a positive voltage supply line, a lower voltage reference, first, second and third positive conductivity transistors and a first negative conductivity transistor having respective control electrodes and current circuits, said first positive and first negative conductivity transistors being connected with their current circuits in series between said positive voltage supply line and said lower voltage reference, said second and third positive conductivity transistors being connected with their current circuits in a series circuit that is connected in parallel with the current circuit of said first positive conductivity transistor, means for applying said HI switching voltage to the control electrodes of said first positive and first negative conductivity transistors, and means setting said second positive conductivity transistor in an ON state.