Variable gain amplifier with temperature compensated gain

Patent metadata

Field	Value
Publication number	US-12028025-B2
Application number	US-202117397833-A
Country	US
Kind code	B2
Filing date	Aug 9, 2021
Priority date	Aug 9, 2021
Publication date	Jul 2, 2024
Grant date	Jul 2, 2024

Abstract

An amplifier with temperature compensation where the amplifier has transistors configured to amplify a received signal to create an amplified signal. The amplifier gain changes over temperature. A gain control circuit, connected to the amplifier, that adjusts the amplifier gain responsive to a gain control signal. A temperature compensation circuit includes numerous elements. A constant current source that generates a constant current which is used to create a constant voltage. A temperature dependent current source that generates a temperature dependent current which is used to create a temperature dependent voltage, such that the temperature dependent current source has an inverse temperature dependance as compared to the amplifier. An operational amplifier compares the constant voltage to the temperature dependent voltage and generates an offset signal which varies over temperature. A gated buffer is configured to receive the offset signal and responsive thereto, selectively modify the gain control signal.

First claim

What is claimed is:

1. An amplifier with temperature compensation comprising:
an amplifier having one or more transistors configured to amplify a received signal to create an amplified signal, the one or more transistor having gain that changes over temperature;
a gain control circuit, connected to the amplifier, configured to adjust the gain of the amplifier responsive to a gain control signal;
a temperature compensation circuit comprising:
a constant current source configured to generate a constant current which is used to create a constant voltage;
a temperature dependent current source configured to generate a temperature dependent current which is used to create a temperature dependent voltage, such that the temperature dependent current source has an inverse temperature dependance as compared to the amplifier;
an operational amplifier configured to compare the constant voltage to the temperature dependent voltage and generate an offset signal which varies over temperature; and
a gated buffer configures to receive the offset signal and responsive thereto, selectively modify the gain control signal.

2. The amplifier with temperature compensation of claim 1 wherein the temperature dependent current source varies over temperature inversely to the gain of the amplifier.

3. The amplifier with temperature compensation of claim 1 wherein the two or more transistors have a negative temperature coefficient that changes gain over changes in temperature.

4. The amplifier with temperature compensation of claim 1 wherein the gain control circuit includes one or more FETs and the gain control signal adjusts the resistance of the FETs in the gain control circuit.

5. The amplifier with temperature compensation of claim 1 wherein the offset signal is used to adjust a resistance that generates the temperature dependent voltage.

6. The amplifier with temperature compensation of claim 1 wherein the gated buffer receives a control signal to control gain and the control signal is modified by the offset signal.

7. An amplifier with a temperature compensated gain control comprising:
an amplifier configured to amplify a received signal to create an amplified signal, the amplifier having a temperature coefficient that causes the gain to vary with changes in temperature such that the gain is determined based on a gain control signal;
a gain control circuit configured to generate the gain control signal based on a control signal, wherein the gain control circuit comprises:
two or more devices that function as variable resistors;
a buffer which receives the control signal and a gain offset signal, and modifies the control signal based on the gain offset signal;

a temperature compensation circuit configured to generate thea gain offset signal which selectively modifies the gain control signal such that the temperature compensation circuit has a temperature coefficient that is inverse to that of the amplifier; and
a feedback loop, that is part of the temperature compensation circuit, the feedback loop configured with an operational amplifier which generates the gain offset signal such that the gain offset signal changes with changes in temperature.

8. The amplifier of claim 7 wherein the amplifier has a negative temperature coefficient and the temperature compensation circuit has a positive temperature coefficient.

9. The amplifier of claim 7 wherein the amplifier has a positive temperature coefficient and the temperature compensation circuit has a negative temperature coefficient.

10. The amplifier of claim 7 wherein the devices that function as variable resistors comprise transistors.

11. The amplifier of claim 7 wherein the temperature compensation circuit includes a current source which generates and output which is temperature dependent.

12. A method for temperature compensating amplifier gain comprising:
providing an amplifier having a temperature coefficient that causes the gain of the amplifier to change with changes in temperature;
providing a temperature compensation circuit that generates a gain offset signal such that the temperature compensation circuit has a temperature coefficient which is the inverse of the amplifier's temperature compensation circuit;
receiving an input signal for amplification;
amplifying the signal with an amplifier to create an amplified signal, the level of amplification determined by a gain control signal;
generating a gain offset signal with the temperature compensation circuit such that the gain offset signal counteracts the effects of temperate change induced gain variation in the amplifier to thereby maintain linearity in the amplified signal over temperature; and
receiving a control signal and the gain offset signal at a buffer and modifying the control signal with the gain offset signal to generate the gain control signal.

13. The method of claim 12 wherein the amplifier includes one or more transistors which have a negative temperature coefficient and the temperature compensation circuit includes one or more current sources which have a positive temperature coefficient.

14. The method of claim 12 wherein the gain control signal comprises two or more signals which are provided to two or more FETs to selectively adjust the resistance across the two or more FETS, which in turn controls the gain of the amplifier.

15. The method of claim 12 further comprising generating the gain offset signal with a feedback loop within the temperature compensation circuit such that the feedback loop includes a feedback signal that changed with changes in temperature.

Assignees

• Macom Tech Solutions Holdings Inc

Inventors

• Francis John R

Classifications

• H03F3/45484

  in differential amplifiers with bipolar transistors as the active amplifying circuit (H03F3/4578 takes precedence) · CPC title

• H03G2201/103

  being an amplifying element · CPC title

• H03G3/30

  in amplifiers having semiconductor devices · CPC title

• H03F2200/447

  the amplifier being protected to temperature influence · CPC title

• H03F3/45475

  using IC blocks as the active amplifying circuit · CPC title