DIFFERENTIAL AMPLIFIER WITH CONTROLLED GAIN Russian patent published in 2010 - IPC H03G3/30 H03F3/45 

FIELD: physics, radio.

SUBSTANCE: invention relates to radio engineering and communication and can be used as a broadband amplifier whose voltage transfer ratio depends on the control signal level u_c, for example in analogue microcircuit structures for various functional purposes, automatic gain control systems, analogue signal multipliers etc. The differential amplifier (DA) has first (1) and second (2) input transistors (T) of a parallel-balance cascade, whose emitters are connected to the current input (3) of the parallel-balance cascade, the bases are connected to the corresponding first (4) and second (5) main inputs of the DA, and the collectors are connected to the first (6) and second (7) outputs of the DA and to the load circuit (8), first (9) and second (10) T of the gain control circuit (GCC), whose bases are connected to the control input (11) of the DA, the emitters are connected to the first (12) reference current source (RCS), and the collectors are connected to the first (6) and second (7) outputs of the DA. The circuit includes an additional resistor (13) and an additional RCS (14), where the additional resistor (13) is connected between the joined emitters of the first (9) and second (10) T of the GCC and the current input (3) of the parallel-balance cascade, which is connected to the additional RCS (14).

EFFECT: lower power supply voltage and increased linearity of the gain control characteristic.

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