Integrated temperature-compensated amplifier circuit

• US 6,104,243 A
• Filed: 05/28/1999
• Issued: 08/15/2000
• Est. Priority Date: 05/29/1998
• Status: Expired due to Term

• Current Assignee: STMicroelectronics GmbH (STMicroelectronics NV)
• Original Assignee: STMicroelectronics GmbH (STMicroelectronics NV)
• Inventors: Viebach, Michael
• Primary Examiner(s): Pascal, Robert
• Assistant Examiner(s): Nguyen, Patricia T.
• Application Number:
  US09/322,966
• Time in Patent Office: 445 Days
• Field of Search: 330/256, 330/289, 327/350, 327/362
• US Class Current: 330/256
• CPC Class Codes: G06G 7/24 for evaluating logarithmic or exponential functions, e.g. hyperbolic functions for multiplication, division or for evaluating powers or roots using logarithmic functions; gamma correction in television systems H04N5/20, H04N9/69
• CPC Class Codes: H03F 1/301 in MOSFET amplifiers H03F1/303, H03F1/305, H03F1/308 take precedence
• CPC Class Codes: H03G 7/00 Volume compression or expansion in amplifiers frequency dependent H03G9/00

Abstract

In a fully integrated logarithmic amplifier, an input current is fed via a diode, and in a reference current branch parallel thereto, a constant current flows through a similar diode. A voltage divider forms of the differential voltage between the two diodes a partial voltage on a variable resistor of the voltage divider, which is processed by a differential amplifier for forming the output signal. Parallel to the two current branches mentioned, there is provided an additional current branch having a constant current source and a diode. The differential voltage between the diode of the reference current branch and the diode in the additional current branch is also divided by a voltage divider. A differential amplifier forms of the voltage on the variable resistor of the voltage divider an error signal which changes the variable resistance from which the differential amplifier has formed the error signal as well as the resistance fo the variable resistor of which the output signal is formed. As the voltage in the two variable resistors of each voltage divider is temperature-independent, the output signal of the amplifier is temperature-independent as well.

Claims

1. An integrated, temperature-compensated amplifier circuit forming of an input signal, by means of a first component having predetermined characteristics, an output signal corresponding to said characteristics, said circuit comprising the following features:

an input current branch containing the first component;

a reference current branch containing a second component and supplying a constant current;

a first differential amplifier having a first input node coupled to the first component, a second input mode coupled to the second component, and an output, wherein the first differential amplifier amplifies a value derived from a first differential voltage between the input nodes in order to form the output signal of the amplifier at the output;

for temperature compensation, there are provided two current branches each carrying a constant current and each having a component with identical characteristics as the first and second components, as well as a second differential amplifier amplifying a value derived from a second differential voltage between the input nodes of the two components in the two current branches, in order to form an error signal;

for the first and second differential voltages, there is provided one controllable voltage divider each, having a partial voltage tapping means and being fed with the error signal as control signal, and

the first and second differential amplifiers are connected to the partial voltage tapping means of the associated controllable voltage divider.

2. The amplifier circuit of claim 1 wherein the amplifier circuit is a logarithmic amplifier and the components are diodes or bipolar transistors.

3. The amplifier circuit of claim 1 wherein each controllable voltage divider comprises as variable resistor a MOSFET having a gate to which the error signal is supplied.

4. The amplifier circuit of claim 1 wherein each controllable voltage divider is formed of a plurality of MOSFETs having gates to which the error signal is supplied.

5. The amplifier circuit of claim 1 wherein the first and the second differential amplifier are each connected to the partial voltage tapping means of the controllable voltage divider, with a temperature-independent constant voltage source being present in one input branch of the second differential amplifier.

6. The amplifier circuit of claim 1 wherein one of the two current branches provide for temperature compensation is identical with the reference current branch.

7. The amplifier circuit of claim 1 wherein the component in one of the current circuits provided for temperature compensation has a greater or a smaller defined component area than the component in the other one of these circuits.

8. An integrated, temperature-compensated amplifier circuit including a first component having predetermined characteristics, that can accept an input signal and produce an output signal corresponding to said characteristics, said circuit comprising:

an input current branch containing the first component;

a reference current branch containing a second component and supplying a constant current;

a first differential amplifier having a first input node coupled to the first component, a second input mode coupled to the second component, and an output, wherein the first differential amplifier amplifies a value derived from a first differential voltage between the input nodes into the output signal of the amplifier at the output;

a second reference current branch carrying a constant current and having a third component with identical characteristics as the first and second components;

a second differential amplifier having a first input node coupled to the second component, a second input node coupled to the third component, and an output, wherein the second differential amplifier amplifies a value derived from a second differential voltage between the input nodes of the second differential amplifier into an error signal at the output of the second differential amplifier; and

first and second controllable voltage dividers coupled to the first and second differential voltages, respectively, each controllable voltage divider having a partial voltage tapping means and being fed with the error signal as control signal, wherein the first and second differential amplifiers connected to the partial voltage tapping means of the first and second controllable voltage dividers, respectively.

9. The amplifier circuit of claim 8 wherein the amplifier circuit is a logarithmic amplifier and the components are diodes or bipolar transistors.

10. The amplifier circuit of claim 8 wherein each controllable voltage divider comprises as variable resistor a MOSFET having a gate to which the error signal is supplied.

11. The amplifier circuit of claim 8 wherein each controllable voltage divider is formed of a plurality of MOSFETs having gates to which the error signal is supplied.

12. The amplifier circuit of claim 8 wherein the first and the second differential amplifier are each connected to the partial voltage tapping means of the controllable voltage divider, with a temperature-independent constant voltage source being present in one input branch of the second differential amplifier.

13. The amplifier circuit of claim 8 wherein one of the two current branches provided for temperature compensation is identical with the reference current branch.

14. The amplifier circuit of claim 8 wherein the component in one of the current circuits provided for temperature compensation has a greater or a smaller defined component area than the component in the other one of these circuits.

15. An integrated amplifier circuit comprising:

an input current branch coupled through an input component to a reference voltage;

a first and a second reference current branch coupled respectively through first and second components to the reference voltage;

a first differential amplifier coupled between and structured to amplify a first differential voltage between the input component and the first component, the first differential amplifier having an output that is an output of the integrated amplifier circuit;

a second differential amplifier coupled between and structured to amplify a second differential voltage between the first component and the second component into an error signal;

a first controllable resistance coupled between the input component and the first component and controlled by the error signal; and

a second controllable resistance coupled between the first component and the second component and controlled by the error signal.

16. The integrated amplifier circuit of claim 15 further comprising:

a first fixed resistance coupled between the input component and the first component; and

a second fixed resistance coupled between the first component and the second component.

17. The integrated amplifier circuit of claim 15 the input, first, and second components are all diodes.

18. The integrated amplifier circuit of claim 17 wherein the diodes are formed of diode-coupled bipolar transistors.

19. The integrated amplifier circuit of claim 15 wherein the first and second controllable resistances are each formed of a MOSFET.

20. The integrated amplifier circuit of claim 15 wherein the input component differs in area from one of the first and second components.

21. The integrated amplifier circuit of claim 15 wherein current of one of the first and second reference current branches is the same as current in the input current branch.

22. The integrated amplifier circuit of claim 15 where the reference voltage is a ground voltage.