Amplifiers – With semiconductor amplifying device – Including differential amplifier
Patent
1990-08-20
1991-12-10
Mottola, Steven
Amplifiers
With semiconductor amplifying device
Including differential amplifier
330294, H03F 345
Patent
active
050721941
ABSTRACT:
A differential amplifier of the cascode type includes a differential stage having a first (T.sub.1) and a second (T.sub.2) transistor, whose emitters are connected to a first (I.sub.1) and a second (I.sub.2) current source, respectively, and are connected to each other through a first resistor (R.sub.12). The collectors of the first and second transistors are connected to an active load constituted by the collector-emitter path of a third (T.sub.3) and a fourth (T.sub.4) transistor, respectively, in series with a second (R.sub.3) and a third (R.sub.4) resistor, respectively, of which one terminal is connected to a supply voltage source. The third and fourth transistors have their bases connected to a reference voltage source. The base of the first and second transistor are connected through a first (C.sub.1) and a second C'.sub.1) capacitor to a current generator equivalent to a voltage source in parallel with an impedance. In order to improve the current coupling at the input of the amplifier in the case where the impedance is not a self-impedance, a third (C.sub.2) and a fourth (C'.sub.2) capacitor are arranged in series with a first (R.sub.51) and a second (R.sub.61) negative feedback resistor, respectively, between the current generator and a first and a second output, respectively, of the amplifier.
REFERENCES:
patent: 4926135 (1990-05-01), Voorman
patent: 4973917 (1990-11-01), Johnson
Franzblau Bernard
Mottola Steven
U.S. Philips Corporation
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