Current mirror bias compensation circuit

• US 10,439,562 B2
• Filed: 02/28/2018
• Issued: 10/08/2019
• Est. Priority Date: 02/28/2017
• Status: Active Grant

• Current Assignee: pSemi Corporation (Murata Manufacturing Co Limited)
• Original Assignee: pSemi Corporation (Murata Manufacturing Co Limited)
• Inventors: Tokuda, Ikumi, Ranta, Tero Tapio, Bargroff, Keith, Murphy, Christopher C., Englekirk, Robert Mark
• Primary Examiner(s): Nguyen, Hieu P
• Application Number:
  US15/908,354
• Publication Number:
  US 20180262163A1
• Time in Patent Office: 587 Days
• Field of Search: 330285, 330296, 330288-289
• CPC Class Codes: G05F 3/26 Current mirrors
• CPC Class Codes: H03F 1/30 Modifications of amplifiers to reduce influence of variations of temperature or supply voltage or other physical parameters in differential amplifiers H03F3/45479
• CPC Class Codes: H03F 1/56 Modifications of input or output impedances, not otherwise provided for
• CPC Class Codes: H03F 2200/129 there being a feedback over the complete amplifier
• CPC Class Codes: H03F 2200/408 the output amplifying stage of an amplifier comprising three power stages
• CPC Class Codes: H03F 2200/411 the output amplifying stage of an amplifier comprising two power stages
• CPC Class Codes: H03F 2200/447 the amplifier being protected to temperature influence
• CPC Class Codes: H03F 2200/451 the amplifier being a radio frequency amplifier
• CPC Class Codes: H03F 2200/468 the temperature being sensed
• CPC Class Codes: H03F 3/19 with semiconductor devices only
• CPC Class Codes: H03F 3/195 in integrated circuits
• CPC Class Codes: H03F 3/21 with semiconductor devices only H03F3/245 takes precedence
• CPC Class Codes: H03F 3/245 with semiconductor devices only
• CPC Class Codes: H04B 1/04 Circuits
• CPC Class Codes: H04B 2001/0408 with power amplifiers

Abstract

Temperature compensation circuits and methods for adjusting one or more circuit parameters of a power amplifier (PA) to maintain approximately constant Gain versus time during pulsed operation sufficient to substantially offset self-heating of the PA. Some embodiments compensate for PA Gain “droop” due to self-heating using a Sample and Hold (S&H) circuit. Other embodiments include bias compensation circuits that directly regulate a bias signal to an amplifier stage as a function of localized heating of one or more of amplifier stages. Such bias compensation circuits include physical placement of at least one bias compensation circuit element in closer proximity to at least one amplifier stage than other bias compensation circuit elements. One bias compensation circuit embodiment includes a temperature-sensitive current mirror circuit for regulating the bias signal. Another bias compensation circuit embodiment includes a temperature-sensitive element having a positive temperature coefficient (PTC) for regulating the bias signal.

Claims

1. A radio frequency amplifier including:

(a) one or more amplifier stages, each having a corresponding bias circuit configured to output a corresponding bias current to the corresponding amplifier stage; and

(b) at least one bias compensation circuit, each bias compensation circuit coupled to at least one of the bias circuits and including a current mirror circuit having;

(1) a first transistor coupled to a first constant current source including a variable resistance device in series with a resistor, configured to be coupled to a first source voltage and output a first essentially constant current regardless of fluctuations in the first source voltage, the first transistor positioned at a distance d1 from a specific one of the one or more amplifier stages, and

(2) a second transistor coupled to a second constant current source including a variable resistance device in series with a resistor, configured to be coupled to a second source voltage and output a second essentially constant current regardless of fluctuations in the second source voltage, the second transistor positioned at a distance d2 from that specific one amplifier stage;

wherein d1<

d2, and each bias compensation circuit regulates the corresponding bias current output by the coupled bias circuits as a function of the temperature of the first transistor relative to the temperature of the second transistor.

4. The invention of claim 1 or 2, wherein the first transistor of at least one bias compensation circuit is adjacent the specific one amplifier stage.

5. The invention of claim 1 or 2, wherein the specific one amplifier stage from which the first transistor of at least one bias compensation circuit is positioned at a distance d1 generates a greater amount of heat during operation compared to a second amplifier stage.

6. The invention of claim 5, wherein the bias circuit coupled to the second amplifier stage is regulated by at least one bias compensation circuit having a first transistor positioned at a distance d1 from the specific one amplifier stage generating a greater amount of heat during operation compared to the second amplifier stage.

7. The invention of claim 1 or 2, wherein the second transistor is positioned farther from every amplifier stage than is the first transistor.

8. The invention of claim 1 or 2, wherein the first transistor and the second transistor are bipolar transistors.

9. The invention of claim 1 or 2, wherein the current mirror circuit generates a compensation signal δ

as a function of the temperature of the first transistor relative to the temperature of the second transistor, and wherein the compensation signal δ

regulates the corresponding bias current output by the coupled bias circuits.

10. The invention of claim 1 or 2, wherein the bias compensation circuit further includes an output amplifier device, coupled to the current mirror circuit, for generating a compensation signal kδ

, as a function of the temperature of the first transistor relative to the temperature of the second transistor, and wherein the compensation signal kδ

regulates the corresponding bias current output by the coupled bias circuits, where k is an amplification factor.

11. The invention of claim 1 or 2, wherein the regulated bias current output by each coupled bias circuit offsets Gain droop of the amplifier stages coupled to the bias circuit.

2. A radio frequency amplifier including:

(a) one or more amplifier stages;

(b) one or more bias circuits, each coupled to a corresponding one of the one or more amplifier stages and configured to output a corresponding bias current to the corresponding one amplifier stage; and

(c) at least one bias compensation circuit, each bias compensation circuit including;

(1) a first constant current source outputting a first essentially constant current;

(2) a second constant current source outputting a second essentially constant current; and

(3) a current mirror circuit including;

(A) a first transistor having an input coupled to the first constant current source;

(B) a second transistor, coupled to the first transistor in a current mirror arrangement, the second transistor having an input coupled to the second constant current source, and an output coupled to at least one of the one or more bias circuits for regulating the corresponding bias current output by the coupled bias circuits;

wherein the first transistor is positioned at a distance d1 from a specific one of the one or more amplifier stages, and the second transistor is positioned at a distance d2 from that specific one amplifier stage, wherein d1<

d2.

3. The invention of claim 2, wherein the current mirror circuit regulates the corresponding bias current output by the coupled bias circuits as a function of the temperature of the first transistor relative to the temperature of the second transistor.

12. A radio frequency amplifier including:

(a) one or more amplifier stages;

(b) one or more bias circuits, each coupled to a corresponding one of the one or more amplifier stages and configured to output a corresponding bias current to the corresponding one amplifier stage; and

(c) at least one bias compensation circuit, each bias compensation circuit including;

(1) a first constant current source outputting a first essentially constant current;

(2) a second constant current source outputting a second essentially constant current; and

(3) a current mirror circuit including;

(A) a first transistor having an input coupled to the first constant current source;

(B) a second transistor, coupled to the first transistor in a current mirror arrangement, the second transistor having an input coupled to the second constant current source, and an output coupled to at least one of the one or more bias circuits for regulating the corresponding bias current output by the coupled bias circuits;

wherein the first transistor is positioned at a distance d1 from a specific one of the one or more amplifier stages, and the second transistor is positioned at a distance d2 from that specific one amplifier stage, wherein d1<

d2;

the radio frequency amplifier further including a compensation circuit configured to monitor a target circuit having one or more performance parameters affected by self-heating during operation of the target circuit, wherein the compensation circuit is configured to be coupled to and adjust one or more circuit parameters of the target circuit sufficient to substantially offset the effect of self-heating during operation of the target circuit on the one or more performance parameters, the compensation circuit including;

(a) at least one sensor located with respect to the target circuit so as to measure the temperature T of the target circuit and generate an output signal representing such temperature T;

(b) at least one tracking circuit, each coupled to at least one sensor, configured to capture a temperature T(t=t₀) at a time t₀ after the commencement of operation of the target circuit, and to sample a temperature T(t>

t₀) at times after time t₀ and during operation of the target circuit, the at least one tracking circuit including;

(1) a differential amplifier having a first input coupled to the output signal of a corresponding sensor, a second input, and an output representing the difference between signals applied to the first input and the second input;

(2) a storage capacitor coupled to the second input of the differential amplifier and selectively coupled to the differential amplifier output;

wherein;

(A) in a first phase, the output of the differential amplifier is coupled to the storage capacitor and to the second input of the differential amplifier, such that a charge on the capacitor represents an initial temperature T(t=t₀);

(B) in a second phase, the output of the differential amplifier represents the difference Δ

T between (i) the output signal of the corresponding sensor coupled to the first input and representing the temperature T(t>

t₀), and (ii) the storage capacitor charge coupled to the second input and representing the temperature T(t=t₀); and

(c) a correction circuit, coupled to at least one tracking circuit, for generating a correction signal as a function of Δ

T from the coupled at least one tracking circuit, the correction signal being configured to be coupled to and adjust the one or more circuit parameters of the target circuit sufficient to substantially offset the effect of self-heating during operation of the target circuit on the one or more performance parameters.

13. A radio frequency amplifier including:

(a) one or more amplifier stages;

(b) one or more bias circuits, each coupled to a corresponding one of the one or more amplifier stages and configured to output a corresponding bias current to the corresponding one amplifier stage; and

(c) at least one bias compensation circuit, each bias compensation circuit including;

(1) a first constant current source outputting a first essentially constant current;

(2) a second constant current source outputting a second essentially constant current; and

(3) a current mirror circuit including;

(A) a first transistor having an input coupled to the first constant current source;

(B) a second transistor, coupled to the first transistor in a current mirror arrangement, the second transistor having an input coupled to the second constant current source, and an output coupled to at least one of the one or more bias circuits for regulating the corresponding bias current output by the coupled bias circuits;

wherein the first transistor is positioned at a distance d1 from a specific one of the one or more amplifier stages, and the second transistor is positioned at a distance d2 from that specific one amplifier stage, wherein d1<

d2;

the radio frequency amplifier further including a compensation circuit configured to monitor a target circuit having one or more performance parameters affected by self-heating during operation of the target circuit, wherein the compensation circuit is configured to be coupled to and adjust one or more circuit parameters of the target circuit sufficient to substantially offset the effect of self-heating during operation of the target circuit on the one or more performance parameters, the compensation circuit including;

(a) at least one proximate sensor located relative to the target circuit so as to measure a temperature T(p) of the target circuit;

(b) at least one distant sensor located relative to the target circuit so as to measure a temperature T(d); and

(c) a comparison and correction circuit, coupled to at least one proximate sensor and at least one distant sensor, for determining Δ

T=T(p)−

T(d) and generating a correction signal as a function of Δ

T, the correction signal being configured to be coupled to and adjust the one or more circuit parameters of the target circuit sufficient to substantially offset the effect of self-heating during operation of the target circuit on the one or more performance parameters.