HF amplifier with switchable gain

A circuit for amplifying or attenuating HF signals comprising:

• an NPN bipolar transistor having a base, a collector, an emitter, a base-collector junction and a base-emitter junction, said NPN bipolar transistor arranged in a common emitter configuration, and a selected base voltage applied to the base;
• a switchable voltage source arranged to apply either a first voltage or a second voltage to said collector, said first voltage selected to reverse bias said base-collector junction and forward bias said base-emitter junction, and said second voltage selected to forward bias said base-collector junction;
• said circuit being operable to amplify HF signals applied to said base wherein said switchable voltage source is switched to apply said first voltage to said collector;
• and
• said circuit being operable to attenuate HF signals applied to said base wherein said switchable voltage source is switched to apply said second voltage to said collector while said base voltage is maintained at its original level or varied to control forward bias of said base-collector junction, wherein the varied base voltage level is equal to or more positive than the emitter level and more positive than the collector level.

A method of amplifying or attenuating HF signals comprising:

• configuring an PNP bipolar transistor having a base, a collector, an emitter, a base-collector junction and a base-emitter junction in a common emitter configuration including a switchable voltage source connected to the collector;
• providing a base voltage at said base;
• amplifying HF signals applied to said base by applying a first voltage to said collector through said switchable voltage source, said first voltage selected to reverse bias said base-collector junction and forward bias said base-emitter junction;
• and
• attenuating HF signals applied to said base by applying a second voltage to said collector through said switchable voltage source, said second voltage selected to forward bias said base-collector junction, said second voltage being applied to said collector while said base voltage is maintained at its original level or varied to control forward bias of said base-collector junction, wherein the varied base voltage level is equal to or more negative than the emitter level and more negative than the collector level.

A circuit for amplifying or attenuating HF signals comprising:

• an PNP bipolar transistor having a base, a collector, an emitter, a base-collector junction and a base-emitter junction, said PNP bipolar transistor arranged in a common emitter configuration, and a selected base voltage applied to the base;
• a switchable voltage source arranged to apply either a first voltage or a second voltage to said collector, said first voltage selected to reverse bias said base-collector junction and forward bias said base-emitter junction, and said second voltage selected to forward bias said base-collector junction;
• said circuit being operable to amplify HF signals applied to said base wherein said switchable voltage source is switched to apply said first voltage to said collector;
• and
• said circuit being operable to attenuate HF signals applied to said base wherein said switchable voltage source is switched to apply said second voltage to said collector while said base voltage is maintained at its original level or varied to control forward bias of said base-collector junction, wherein the varied base voltage level is equal to or more negative than the emitter level and more negative than the collector level.