Circuit for converting single-ended input signals to a pair of differential output signals

A gain controlled amplifier circuit comprising first and second diode means connected in a first series circuit;

• third diode means, first transistor means having its collector-emitter circuit connected in a second series circuit with said third diode means, the first and second series circuits being in parallel with each other;
• said first transistor means having its base electrode connected to the junction defined by said first and second diode means such that the base-emitter circuit thereof is in parallel arrangement with said second diode means;
• first current source means connected to the parallel-connected first and second series circuits so as to supply currents thereto;
• means for supplying a single-ended signal to said junction defined by said first and second diode means;
• second transistor means having its base-emitter circuit connected in parallel with said second diode means;
• third transistor means having its base electrode connected to the collector electrode of said first transistor means and its emitter electrode connected to the emitter electrode of said first transistor means, a pair of differential output signal currents flowing through the collector-emitter circuits of said second and third transistor means;
• output differential amplifier means having a pair of differentially-connected transistors whose base electrodes are respectively connected to the collector electrodes of said second and third transistor means and whose emitter electrodes are connected in common;
• second current source means coupled to the common-connected emitter electrodes of said differentially-connected transistors;
• and at least one output terminal coupled to the collector electrode of at least one of said differentially-connected transistors to provide an output signal whose gain is controllable as a function of at least one of said current source means.

A gain-controlled amplifier circuit comprising first and second diode means connected in a first series circuit;

• third diode means;
• first transistor means having its collector-emitter circuit connected in a second series circuit with said third diode means, the first and second series circuits being in parallel with each other;
• said first transistor means having its base electrode connected to the junction defined by said first and second diode means such that the base-emitter circuit thereof is in parallel arrangement with said second diode means;
• first current source means coupled to the parallel-connected first and second series circuits so as to supply currents thereto;
• means for supplying a single-ended signal to said junction defined by said first and second diode means;
• first differential amplifier means having a first pair of differentially-connected transistors whose base electrodes are respectively connected to said junction defined by said first and second diode means and to the collector electrode of said first transistor means and whose emitter electrodes are connected in common, a pair of differential output signal currents flowing through the collector-emitter circuits of said first pair of differentially-connected transistors, respectively;
• second current source means coupled to the common-connected emitter electrodes of said first pair of differentially-connected transistors;
• output differential amplifier means having a second pair of differentially-connected transistors whose base electrodes are respectively connected to the collector electrodes of said first pair of differentially-connected transistors and whose emitter electrodes are connected in common;
• third current source means coupled to the common-connected emitter electrodes of said second pair of differentially-connected transistors;
• and at least one output terminal coupled to the collector electrode of at least one of the second pair of differentially-connected transistors to provide an output signal whose gain is controllable as a function of at least one of said current source means.

A gain-controlled amplifier circuit comprising first and second diode means connected in a first series circuit;

• third diode means;
• first transistor means having its collector-emitter circuit connected in a second series circuit with said third diode means, the first and second series circuits being in parallel with each other;
• said first transistor means having its base electrode connected to the junction defined by said first and second diode means such that the base-emitter circuit thereof is in parallel arrangement with said second diode means;
• first current source means connected to the parallel-connected first and second series circuits so as to supply currents thereto;
• means for supplying a single-ended signal to said junction defined by said first and second diode means;
• bias means coupled to said parallel-connected first and second series circuits to apply a bias voltage thereto;
• differential amplifier means having a pair of differentially-connected transistors whose base electrodes are respectively connected to said junctiondefined by said first and second diode means and to the collector electrode of said first transistor means and whose emitter electrodes are connected in common, a pair of differential output signal currents flowing through the collector-emitter circuits of said pair of differentially-connected transistors, respectively;
• second current source means coupled to the common-connected emitter electrodes of said pair of differentially-connected transistors;
• and at least one output terminal coupled to the collector electrode of at least one of said pair of differentially-connected transistors to provide an output signal whose gain is controllable as a function of at least one of said current source means.