| US 7,489,196 B2 | ||
| Output power control of an RF amplifier | ||
| Michele Vaiana, Paternò (Italy); and Giuseppe Gramegna, Catania (Italy) | ||
| Assigned to STMicroelectronics, S.r.l., Agrate Brianza (MI) (Italy) | ||
| Filed on May 11, 2007, as Appl. No. 11/747,539. | ||
| Claims priority of application No. 06425321.4 (EP), filed on May 12, 2006. | ||
| Prior Publication US 2007/0273448 A1, Nov. 29, 2007 | ||
| Int. Cl. H03G 3/30 (2006.01) | ||
| U.S. Cl. 330—285 [330/289; 330/296] | 17 Claims |
| 1. A control circuit for controlling an output current from an output bipolar power transistor comprising:
a sense network comprising a sense transistor coupled as an emitter-follower to a base of the output bipolar power transistor
for sensing a base current thereof;
an error amplifier for comparing an input bias voltage with a power control signal for generating an output signal;
an input biasing network being controlled by the output signal from said error amplifier for biasing the output bipolar power
transistor;
a control current generator for generating a control current;
a current-scaling circuit coupled to said control current generator and comprising a bipolar transistor of a same type as
said output bipolar power transistor, and through which the control current generated by said control current generator generates
a current-scaled control current to be compared with the sensed base current of said output bipolar power transistor;
a first current-to-voltage converting network coupled to an output of said current-scaling circuit; and
a second current-to-voltage converting network coupled to a collector of said emitter-follower sense transistor;
said error amplifier having a first input coupled to said first current-to-voltage converting network, and a second input
coupled to said second current-to-voltage converting network.
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