RF power amplifier circuit

• US 20030087626A1
• Filed: 10/11/2002
• Published: 05/08/2003
• Est. Priority Date: 10/16/2001
• Status: Active Grant

• Current Assignee: Ampleon Netherlands B.V. (Ampleon Coöperatief UA)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Prikhodko, Dmitry Pavlovich, Kramer, Niels, Van Zuijlen, Albertus Gerardus Wilhelmus Philipus
• Granted Patent: US 6,990,323 B2
• Time in Patent Office: Days
• US Class Current: 455/341
• CPC Class Codes: H03F 1/302 in bipolar transistor amplifiers H03F1/303, H03F1/305, H03F1/307 take precedence
• CPC Class Codes: H03F 1/52 Circuit arrangements for protecting such amplifiers monitoring arrangements G01R31/28; increasing reliability in communication systems, e.g. using redundancy H04B1/74

Abstract

A RF power amplifier circuit has at least one power transistor and a protection circuit protecting the power transistor against high voltages that lead to a destructive breakdown of the transistor. The circuit comprises a power transistor (2), a biasing circuit (6) biasing the power transistor; a peak detector (8) measuring the output voltage of the power transistor; and a comparator circuit (12) connected to the peak detector (8) and designed to reduce the base current of the power transistor (2) when controlled by the peak detector (8).

Claims

1. A RF power amplifier circuit having at least one output power transistor and a protection circuit protecting the power transistor against high voltages that lead to a destructive breakdown of the power transistor, the circuit comprising:

(a) a biasing circuit (6) biasing the power transistor (2);

(b) a peak detector (8) detecting the output voltage of the power transistor; and

(c) a comparator circuit (12) connected to the peak detector (8) and designed to reduce the base current of the power transistor (2) when controlled by the peak detector.

2. The RF power amplifier circuit of claim 1, wherein the biasing circuit (6) comprises a voltage-to-current converter (24) and a biasing transistor (36), the base of the biasing transistor (36) being connected to the comparator circuit.

3. The RF power amplifier circuit of claim 1, wherein the collector of the power transistor (2) is connected to the peak detector (8) via a capacitor (46).

4. The RF power amplifier circuit of claim 1 or 3, wherein the peak detector (8) comprises a diode (52) connected to the capacitor (46) coupling the output signal of the power transistor (2) to the peak detector (8).

5. The RF power amplifier circuit of claim 4, wherein a capacitor (53) is arranged between the diode (52) and ground.

6. The RF power amplifier circuit of anyone of the preceding claims, wherein the peak detector (8) comprises voltage dividing resistors (48,50) connected between the capacitor (46) and ground.

7. The RF power amplifier circuit of claim 6, wherein one or several resistors of the voltage dividing resistors are adjustable.

8. The RF power amplifier circuit of claim 6 or 7, wherein an intermediate node of the voltage dividing resistor arrangement is the output of the peak detector.

9. The RF power amplifier circuit of claim 1, wherein the comparator circuit (12) comprises a transistor (56) and, in series connection, L−

1 diodes 58(1) to 58(L−

1).

10. The RF power amplifier circuit of anyone of the preceding claims, wherein the comparator circuit (12) is connected via a transistor (62) to the base of the biasing transistor (38) of the biasing circuit (6).

11. The RF power amplifier circuit of anyone of the preceding claims, wherein the collector terminal of the input transistor (56) of the comparator circuit (12) is connected to the supply voltage and the emitter is connected to ground through the series of diodes.

12. The RF power amplifier circuit of anyone of the preceding claims, having a plurality of power transistors (70,72,74) each connected to a biasing circuit (82,84,86), wherein the output of the peak detector comprised in a control circuit (100) is connected through a comparator circuit (102) and current mirror transistors (112, 114, 116) to the respective biasing circuits (82,84,86) of the power transistors (70,72,74).

13. The RF power amplifier circuit of anyone of the preceding claims, comprising a switch (10) which is connected between Vsupply and the peak detector (8), the ON and OFF state of the switch being controlled by Vcontrol.

14. The RF power amplifier circuit of anyone of the preceding claims, comprising a filter comprising resistors (40,42) and a capacitor (44) connected from a node between the resistors (40,42) to ground, which filter is arranged between the switch (10) and the peak detector (8).

15. A wireless communication device comprising an RF power amplifier circuit having at least one output power transistor and a protection circuit protecting the power transistor against high voltages that lead to a destructive breakdown of the power transistor, the circuit comprising:

(a) a biasing circuit (6) biasing the power transistor (2);

(b) a peak detector (8) detecting the output voltage of the power transistor; and

(c) a comparator circuit (12) connected to the peak detector (8) and designed to reduce the base current of the power transistor (2) when controlled by the peak detector.