Level shifter

• US 10,312,913 B2
• Filed: 10/02/2017
• Issued: 06/04/2019
• Est. Priority Date: 10/17/2016
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Tokai RIKA Denki Seisakusho
• Original Assignee: Kabushiki Kaisha Tokai RIKA Denki Seisakusho
• Inventors: Matsubara, Junichi
• Primary Examiner(s): Hiltunen, Thomas J.
• Application Number:
  US15/722,449
• Publication Number:
  US 20180109260A1
• Time in Patent Office: 610 Days
• CPC Class Codes: H03K 19/00307 in bipolar transistor circuits
• CPC Class Codes: H03K 19/00315 in field-effect transistor circuits
• CPC Class Codes: H03K 19/017518 using a combination of bipolar and field effect transistors [BIFET]
• CPC Class Codes: H03K 19/01831 with at least one differential stage
• CPC Class Codes: H03K 19/0813 Threshold logic
• CPC Class Codes: H03K 19/0944 using MOSFET or insulated gate field-effect transistors, i.e. IGFETH03K19/096 takes precedence
• CPC Class Codes: H03K 3/02337 Bistables with hysteresis, e.g. Schmitt trigger non-regenerative amplitude discriminators G01R19/165
• CPC Class Codes: H03K 5/082 with an adaptive threshold

Abstract

The present disclosure provides a level shifter including: a level shifter section that is driven by a first power source voltage, and that, in accordance with switching of an input signal of a voltage lower than the first power source voltage, switches an output signal that has been level-shifted, from the first power source voltage to a voltage lower than the first power source voltage; and a threshold voltage changing circuit that, in accordance with a switching direction of the input signal, changes a threshold voltage of the input signal for switching the output signal.

Claims

1. A level shifter comprising:

a level shifter section that is driven by a first power source voltage, and that, in accordance with switching of an input signal of a voltage lower than the first power source voltage, switches an output signal that has been level-shifted, from the first power source voltage to a voltage lower than the first power source voltage; and

a threshold voltage changing circuit that, in accordance with a switching direction of the input signal, changes a threshold voltage of the input signal for switching the output signal,

wherein the level shifter section includes a differential amplifier circuit and a current mirror circuit, and

wherein the threshold voltage changing circuit includes;

a constant current source having an input connected to the first power source voltage;

a first transistor having a first electrical conductivity type and having a first main electrode connected to an output of the constant current source, a second main electrode connected to a second power source voltage having a voltage lower than the first power source voltage, and a first control electrode connected to a node between an output terminal where the output signal is output and the differential amplifier circuit; and

a second transistor having a second electrical conductivity type opposite to that of the first electrical conductivity type and having a third main electrode connected to the differential amplifier circuit, a fourth main electrode connected to the differential amplifier circuit and the output terminal, and a second control electrode connected to a node between the output of the constant current source and the first main electrode.

2. The level shifter of claim 1, wherein the threshold voltage changing circuit is a hysteresis circuit exhibiting hysteresis characteristics with respect to changes in a voltage of the output signal in response to changes in the voltage of the input signal.

3. The level shifter of claim 1, wherein

the differential amplifier circuit includes:

a third transistor having a fifth main electrode connected to the first power source voltage, a sixth main electrode connected to the second power source voltage, and a third control electrode connected via a resistor to an input terminal to which the input signal is input,

a fourth transistor having a seventh main electrode connected to the first power source voltage and an eighth main electrode connected to a fourth control electrode of the fourth transistor and to the output terminal, and

a fifth transistor having the first electrical conductivity type and having a ninth main electrode connected to the eighth main electrode and the output terminal and a tenth main electrode connected to the second power source voltage; and

the current mirror circuit includes;

the fifth transistor, and

a sixth transistor having the first electrical conductivity type and having an eleventh main electrode connected to the first power source voltage, a twelfth main electrode connected to the second power source voltage, and a sixth control electrode connected to a fifth control electrode of the fifth transistor.

4. The level shifter of claim 1, wherein:

the constant current source and the second transistor are configured by an offset transistor, and

the first transistor is configured by a vertical diffused transistor.

5. The level shifter of claim 1, further comprising a clamp section that limits the amplitude of the output signal.