OUTPUT FILTER FOR AN ELECTRONIC CIRCUIT

• US 20200136591A1
• Filed: 10/25/2019
• Published: 04/30/2020
• Est. Priority Date: 10/26/2018
• Status: Active Grant

• Current Assignee: Nexperia B.V. (Wingtech Technology Co., Ltd.)
• Original Assignee: Nexperia B.V. (Wingtech Technology Co., Ltd.)
• Inventors: ASAM, Geethanadh, HORSTINK, Harrie
• Granted Patent: US 10,917,073 B2
• Time in Patent Office: Days
• CPC Class Codes: H01L 27/0266 using field effect transistors as protective elements
• CPC Class Codes: H01L 27/0288 using passive elements as protective elements, e.g. resistors, capacitors, inductors, spark-gaps
• CPC Class Codes: H02H 9/046 responsive to excess voltage appearing at terminals of integrated circuits protection by specific structural integration design H01L27/0248
• CPC Class Codes: H03H 11/04 Frequency selective two-port networks

Abstract

This disclosure relates to a filter circuit for an output stage of an electronic circuit. The filter circuit includes a capacitor connected between a supply voltage and a first transistor. The first transistor is arranged as a diode connected transistor; a second transistor is connected to the first transistor so that the first and second transistors are arranged as a current mirror. The capacitor is connected to the first and second transistors and configured and arranged so that during operation the first transistor, the second transistor and the capacitor operate as a high pass filter.

Claims

1. A filter circuit for an output stage of an electronic circuit, the filter circuit comprising:

a capacitor connected between a supply voltage terminal and a first transistor;

wherein the first transistor is arranged as a diode connected transistor;

a second transistor connected to the first transistor so that the first and second transistors are arranged as a current mirror; and

wherein the capacitor is connected to the first and second transistors and configured and arranged so that during operation the first transistor, the second transistor and the capacitor operate as a high pass filter.

2. The filter circuit of claim 1, wherein the capacitor is connected to a source and a gate of the first transistor, and a gate of the second transistor.

3. The filter circuit of claim 1, wherein the first transistor has an impedance of the high pass filter.

4. The filter circuit of claim 2, wherein the first transistor has an impedance of the high pass filter.

5. The filter circuit of claim 1, wherein the first and second transistors and the capacitor have a gate source capacitance, and

wherein the high pass filter has a capacitance that is the gate source capacitance.

6. The filter circuit of claim 4, wherein the first and second transistors and the capacitor have a gate source capacitance, and wherein the high pass filter has a capacitance that is the gate source capacitance

7. The filter circuit of claim 3, further comprising a first filter transistor having an impedance, and wherein the first transistor has a gate-source impedance that is the impedance of the first filter transistor.

8. The filter circuit of claim 1, wherein the capacitor and the first transistor are configured an arranged to detect a change in the supply voltage.

9. The filter circuit of claim 6, wherein the capacitor and the first transistor are configured an arranged to detect a change in the supply voltage.

10. The filter circuit of claim 1, wherein the capacitor has a capacitance greater than a combined capacitance of the first transistor and the second transistor.

11. The filter circuit of claim 5, wherein the capacitor has a capacitance greater than a combined capacitance of the first transistor and the second transistor.

12. The filter circuit of claim 1, wherein the second transistor is arranged to be connected to the output stage, and wherein the output stage is a CMOS driver.

13. The filter circuit of claim 11, wherein the second transistor is arranged to be connected to the output stage;

and wherein the output stage is a CMOS driver.

14. The filter circuit of claim 1, wherein the second transistor is connected to a further circuit, and wherein the further circuit has a capacitive load and a resistive load.

15. The filter circuit of claim 1, further comprising

an enable circuit to switchably operate the filter circuit, wherein the enable circuit comprises a third transistor connected to a source of the first transistor;

and

a supply voltage detection circuit is connected to a gate of the third transistor.

16. The filter circuit of claim 1, further comprising a resistor connected between the first transistor and the capacitor, wherein the resistor is arranged to absorb electro-static discharge (ESD) events.

17. An output stage of an electronic circuit comprising the filter of claim 1.

18. A logic circuit comprising the output stage of claim 17.