Bias current generation circuit

Patent metadata

Field	Value
Publication number	US-11455000-B2
Application number	US-202117182267-A
Country	US
Kind code	B2
Filing date	Feb 23, 2021
Priority date	Feb 25, 2020
Publication date	Sep 27, 2022
Grant date	Sep 27, 2022

Abstract

The present invention discloses a bias current generation circuit. An operation amplifier compares an input voltage having a zero-temperature coefficient and a feedback voltage to generate a driving voltage. An output transistor generates a bias current according to the driving voltage. A variable resistive circuit is electrically coupled to the output transistor through a feedback node to generate the feedback voltage according to the bias current and includes series-coupled resistors and switch transistors. Each of the resistors has a resistance having a positive temperature coefficient and includes a current input terminal and a current output terminal. Each of the switch transistors is electrically coupled between the current output terminal of one of the resistors and a ground terminal. One of the switch transistors turns on according to a control voltage variable according to the temperature variation to enable resistors to generate the resistance having a negative temperature coefficient.

First claim

What is claimed is:

1. A circuit, comprising:
an operation amplifier comprising at least two input terminals and an output terminal, wherein the at least two input terminals are respectively configured to receive an input voltage having a zero-temperature coefficient and a feedback voltage to generate a driving voltage at the output terminal according to a comparison result between the input voltage and the feedback voltage;
an output transistor configured to generate a bias current according to the driving voltage; and
a variable resistive circuit electrically coupled to the output transistor through a feedback node and configured to generate the feedback voltage according to the bias current, wherein the variable resistive circuit comprises:
a plurality of resistors electrically coupled in series each having a load resistance and a positive-temperature coefficient and each having a current input terminal and a current output terminal; and
a plurality of switch transistors each electrically coupled between the current output terminal of one of the resistors and a ground terminal, wherein one of the switch transistors turns on according to a control voltage variable with a temperature change to enable the corresponding one of the resistors and generates a transistor resistance having a negative temperature coefficient.

2. The circuit of claim 1 , wherein an increased amount of the load resistance of each of the resistors generated due to the increase of the temperature and a decreased amount of the transistor resistance generated due to the increase of the temperature together keep a total resistance of the variable resistive circuit within a predetermined range.

3. The circuit of claim 1 , further comprising a bandgap circuit configured to generate the input voltage having the zero-temperature coefficient.

4. The circuit of claim 3 , wherein each of the switch transistors is an N-type transistor and the circuit further comprises:
a load resistor electrically coupled between a control terminal and the ground terminal; and
a positive-temperature coefficient current source electrically coupled to the control terminal and configured to provide a control current having the positive-temperature coefficient according to the operation of the bandgap circuit to the load resistor to generate the control voltage at the control terminal, wherein the control voltage has the positive-temperature coefficient.

5. The circuit of claim 3 , wherein each of the switch transistors is a P-type transistor and the circuit further comprises:
a load resistor electrically coupled between a voltage source and the control terminal; and
a positive-temperature coefficient current source electrically coupled between the control terminal and the ground terminal and configured to provide a control current having the positive-temperature coefficient according to the operation of the bandgap circuit to generate the control voltage at the control terminal, wherein the control voltage has the negative-temperature coefficient.

6. The circuit of claim 1 , wherein the output transistor comprises a gate configured to receive the driving voltage, and the circuit further comprises a calibration switch configured to electrically couple the gate to the ground terminal under a calibration mode and to electrically isolate the gate from the ground terminal to receive the driving voltage under an operation mode.

7. The circuit of claim 6 , wherein the feedback node is further configured to receive a calibration current under the calibration mode and control one of the switch transistors to turn one under the calibration mode such that a total resistance of the variable resistive circuit makes a voltage at the feedback node generated according to the calibration current equals to a target voltage.

8. The circuit of claim 7 , wherein the target voltage is set according to a manufacturing process deviation parameter.

9. The circuit of claim 1 , wherein the bias current is outputted to an external circuit through a current mirror.

10. The circuit of claim 1 , wherein the operation amplifier, the output transistor and the variable resistive circuit are disposed inside a single chip.

Assignees

• Realtek Semiconductor Corp

Inventors

• Ho Chun-Ta
• Kuo Chun-I
• Min Shawn

Classifications

• G05F1/462

  as a function of the requirements of the load, e.g. delay, temperature, specific voltage/current characteristic · CPC title

• G05F1/575

  characterised by the feedback circuit · CPC title

• G05F1/461

  using an operational amplifier as final control device · CPC title

• G05F3/262 Primary

  using field-effect transistors only · CPC title

• G05F1/463

  Sources providing an output which depends on temperature · CPC title