Abstract A bias arrangement makes it possible to automatically compensate the temperature drift occuring in an amplifier transistor. The bias arrangement formed by a first and a second transistor, supplies the bias voltage for an amplifier transistor, which voltage is variable by a variable resistor in the emitter lead of the first transistor. A third transistor identical to the first transistor assembled on the same radiator as the first transistor and the amplifier transistor supplies to the base of the amplifier transistor a voltage proportional to the temperature variations, with a coefficient which is chosen by means of a resistance bridge, in order to precisely compensate the variations the amplifier transistor.
A power amplifier comprising at least one amplifier transistor having a base, an emitter and a collector, said amplifier transistor for amplifying an input signal being arranged in a common emitter configuration at least as far as the bias is concerned and an arrangement for supplying a bias voltage to the base of said amplifier transistor, said arrangement including: an auxiliary transistor having a base, a collector and an emitter, the emitter of said auxiliary transistor being coupled to the base of said amplifier transistor; a regulating transistor having a base, a collector and an emitter, the collector of said regulating transistor being coupled to the base of said auxiliary transistor; a resistor inserted between the base of said regulating transistor and the emitter of said auxiliary transistor; a further transistor, having the same characteristics as said regulating transistor and having a base, a collector and an emitter, the emitter of said further transistor being coupled to the emitter of said auxiliary transistor; a variable resistor inserted between the base of said regulating transistor and the base of said further transistor, the base and collector of said further transistor being coupled; and means for adjusting the emitter voltage of said regulating transistor; said amplifier transistor, said regulating transistor and said further transistor being assembled on one and the same radiator.
Claim 2
Dependent Claim
220 words
A power amplifier comprising at least one amplifier transistor having a base, an emitter and a collector, said amplifier transistor for amplifying an input signal being arranged in a common emitter configuration at least as far as the bias is concerned and an arrangement for supplying a bias voltage to the base of said amplifier transistor, said arrangement including: an auxiliary transistor having a base, a collector and an emitter, the emitter of said auxiliary transistor being coupled to the base of said amplifier transistor; a regulating transistor having a base, a collector and an emitter, the collector of said regulating transistor being coupled to the base of said auxiliary transistor; a resistor inserted between the base of said regulating transistor and the emitter of said auxiliary transistor; a further transistor, having the same characteristics as said regulating transistor and having a base, a collector and an emitter, the emitter of said further transistor being coupled to the emitter of said auxiliary transistor; a variable resistor inserted between the base of said regulating transistor and the base of said further transistor, the base and collector of said further transistor being coupled; and means for adjusting the emitter voltage of said regulating transistor; said amplifier transistor, said regulating transistor and said further transistor being assembled on one and the same radiator.
Claim 3
Dependent Claim
20 words
A power amplifier as claimed in claim 1 wherein said regulating transistor and said further transistor have a common substrate.
Claim 4
Dependent Claim
17 words
A power amplifier as claimed in claim 2 wherein said auxiliary transistor is assembled on said radiator.