Power amplifier with low noise figure and voltage variable gain
View Patent ↗The object of the present invention is a low noise figure amplifier with a variable gain which comprises a cascode amplification stage comprising, serially mounted, a low-voltage MOSFET transistor installed as a common source followed by a bipolar transistor with high breakdown voltage installed as a common base. A resistor is placed between the bipolar transistor's collector and the grid of the cascode stage's MOSFET transistor, and the cascode stage is electrically powered through a choke.
1. An integrated power amplifier with low noise figure and variable gain, comprising a cascode amplification stage which comprises, connected serially,
a low-voltage MOSFET transistor installed as a common source, followed by
a bipolar transistor with a high breakdown voltage, at least twice the voltage of the MOSFET transistor, installed as a common base,
a feedback resistor being placed between the bipolar transistor's collector and the grid of the cascode stage's MOSFET transistor, and
the cascode stage being electrically powered through a choke connected to the collector of the bipolar transistor.
2. An amplifier according to claim 1 , further comprising an interface circuit for controlling the base voltage of the bipolar transistor as a function of the gain to be obtained.
3. An amplifier according to claim 2 , wherein the interface circuit may further comprise a resistor combined with a capacitor, in order to filter the outside noise transmitted to the amplifier.
4. An amplifier according to claim 1 , further comprising at least one digital-to-analog converter for digitally controlling the amplifier.
5. An amplifier according to claim 1 , further comprising at least one switchable attenuator at the output of the cascode stage.
6. An amplifier according to claim 1 , further comprising at least one switchable attenuator at the input of the cascode stage.
7. An amplifier according to claim 5 , wherein the supply voltage imposed at the input of the switchable attenuator's command circuit is of the same order of magnitude as the supply voltage of the cascode stage, a voltage less than the supply voltage of the cascode stage being imposed at the source and drain of the switchable attenuator's MOSFET transistor.