Abstract The bias circuit of the base of an HF amplifier transistor, arranged in a common-emitter configuration, comprises an LF transistor likewise in a common-emitter configuration and two resistors respectively connecting the base of the LF transistor to its collector and to a point of fixed potential. The bias voltage varies more rapidly, as a function of temperature, than the voltage across the terminals of the reference diode formed by the base-emitter junction of the LF transistor. This permits a correct temperature compensation of the HF transistor in spite of the temperature differences between the junctions of the HF and LF transistors and of the thermal inertia of the thermal link between these two transistors.
A class AB power amplifier comprising: an amplifier transistor designed to amplify an HF signal applied to its base, said amplifier transistor being connected in a common-emitter configuration at least as far as the bias is concerned, and having an emitter, a base and a collector, the latter being coupled to a fixed potential point; and a base bias circuit for biasing said amplifier transistor, said circuit comprising a regulating transistor arranged in a common-emitter configuration, and having an emitter, a base and a collector, the latter being coupled to the base of said amplifier transistor, and first and second resistors connecting the base of said regulating transistor respectively to its collector and to said fixed potential point.
Claim 2
Dependent Claim
118 words
A class AB power amplifier comprising: an amplifier transistor designed to amplify an HF signal applied to its base, said amplifier transistor being connected in a common-emitter configuration at least as far as the bias is concerned, and having an emitter, a base and a collector, the latter being coupled to a fixed potential point; and a base bias circuit for biasing said amplifier transistor, said circuit comprising a regulating transistor arranged in a common-emitter configuration, and having an emitter, a base and a collector, the latter being coupled to the base of said amplifier transistor, and first and second resistors connecting the base of said regulating transistor respectively to its collector and to said fixed potential point.
Claim 3
Dependent Claim
27 words
A class AB power amplifier as claimed in claim 1, wherein said amplifier transistor and said regulating transistor are assembled on one and the same heat sink.