Positive Temperature Coefficient Bias Compensation Circuit

• US 20180262166A1
• Filed: 02/28/2018
• Published: 09/13/2018
• 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: Takagi, Tsuyoshi, Ranta, Tero Tapio, Bargroff, Keith, Murphy, Christopher C., Englekirk, Robert Mark
• Granted Patent: US 10,439,563 B2
• Time in Patent Office: Days
• CPC Class Codes: H03F 1/301 in MOSFET amplifiers H03F1/303, H03F1/305, H03F1/308 take precedence
• CPC Class Codes: H03F 1/302 in bipolar transistor amplifiers H03F1/303, H03F1/305, H03F1/307 take precedence
• CPC Class Codes: H03F 1/56 Modifications of input or output impedances, not otherwise provided for
• CPC Class Codes: H03F 2200/21 Bias resistors are added at the input of an amplifier
• CPC Class Codes: H03F 2200/222 A circuit being added at the input of an amplifier to adapt the input impedance of the amplifier
• CPC Class Codes: H03F 2200/267 A capacitor based passive circuit, e.g. filter, being used in an amplifying circuit
• CPC Class Codes: H03F 2200/387 A circuit being added at the output of an amplifier to adapt the output impedance of the amplifier
• CPC Class Codes: H03F 2200/408 the output amplifying stage of an amplifier comprising three 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 2200/474 A current mirror being used as sensor
• CPC Class Codes: H03F 3/195 in integrated circuits
• CPC Class Codes: H03F 3/213 in integrated circuits
• CPC Class Codes: H03F 3/245 with semiconductor devices only
• CPC Class Codes: H03F 3/45183 Long tailed pairs H03F3/4521, H03F3/45237 take precedence
• CPC Class Codes: H03F 3/68 Combinations of amplifiers, e.g. multi-channel amplifiers for stereophonics power amplifiers using a combination of several semiconductor amplifiers H03F3/211; combinations of amplifiers using coupling networks with distributed constants H03F3/602
• CPC Class Codes: H03G 2201/708 being temperature
• CPC Class Codes: H03G 3/3042 in modulators, frequency-changers, transmitters or power amplifiers transmission power control in bidirectional transmission systems H04W52/04

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 having an output coupled in parallel with the output of at least one of the bias circuits and including a positive temperature coefficient (PTC) device configured to be coupled to a power supply voltage and being coupled to the output of the bias compensation circuit, the PTC device being positioned at a distance d1 from a specific one of the one or more amplifier stages and outputting a compensation current that is a function of the temperature of the PTC device.

3. The invention of claim 1 or 2, wherein the compensation current from each bias compensation circuit supplements the bias current output by the bias circuits coupled to such bias compensation circuit as a function of the temperature of the PTC device of such bias compensation circuit relative to the temperature of the bias circuits.

4. The invention of claim 1 or 2, wherein the PTC device 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 PTC device 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 output of the bias circuit coupled to the second amplifier stage is coupled to the output of at least one bias compensation circuit having a PTC device 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 each bias circuit having an output coupled to the output of one of the at least one bias compensation circuits is positioned farther from every amplifier stage than is the PTC device of such coupled bias compensation circuits.

8. The invention of claim 1 or 2, further including a resistor coupled between the PTC device and the output of the bias compensation circuit, for regulating the compensation current.

9. The invention of claim 8, wherein the resistor is settable or variable.

10. The invention of claim 1 or 2, wherein the compensation current output by a specific one of the at least one bias compensation circuits offsets Gain droop of the amplifier stages coupled to the bias circuits coupled in parallel with the specific one bias compensation circuit.

11. The invention of claim 1 or 2, wherein the PTC device is a PTC transistor or a diode.

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 having an output coupled in parallel with the output of at least one of the bias circuits and including a positive temperature coefficient (PTC) device configured to be coupled to a power supply voltage and being coupled to the output of the bias compensation circuit, the PTC device being positioned at a distance d1 from a specific one of the one or more amplifier stages and outputting a compensation current through the resistor that is a function of the temperature of the PTC device;

wherein each bias circuit coupled to a specific one of the at least one bias compensation circuits is positioned at a distance of at least d2 from all amplifier stages, and d1<

d2.

12. The invention of claim 2, 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; and

(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. The invention of claim 2, 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.

14-26. -26. (canceled)