Compace HBT wide band microwave variable gain active feedback amplifier

A variable gain amplifier comprising:

• first transistor including a base, an emitter, and a collector;
• first parallel feedback means connected to the collector and the base of the first transistor for providing an active feedback inductive impedance;
• second parallel feedback means connected to the collector and the base of the first transistor for providing a variable resistive impedance and including a monolithically integrated p-i-n diode having a quiescent bias current flowing therethrough, wherein a gain response of said first transistor is related to the variable resistive impedance of said second parallel feedback means;
• control means for controlling the quiescent bias current flowing through said p-i-n diode to vary said variable resistive impedance;
• a second transistor connected to said first transistor to form a Darlington pair and having a base, an emitter, and a collector, wherein the collector of the first transistor is connected to the collector of the second transistor and the emitter of the first transistor is connected to the base of the second transistor;
• and
• a network means in said first parallel feedback path for providing an active feedback inductive impedance including
• a first tuning capacitor,
• third and fourth transistors each including an emitter, a base and a collector, wherein the emitter of the third transistor is connected to the collector of the second transistor, and wherein the base of the third transistor and the emitter of the fourth transistor are coupled by the first tuning capacitor,
• first tuning resistor connected to the collector of the third transistor,
• second tuning resistor connected to the base of the fourth transistor,
• a collector resistor connected to said collectors of said first and second transistors,
• first biasing resistor connected to the base of the third transistor, to the first tuning resistor and to the collector resistor, wherein the active feedback inductive impedance of said inductive network means is related to a capacitance of said first tuning capacitor and to resistance values of said first and second tuning resistors.