A low-noise wide-band bipolar transistor amplifier in which distortion caused by non-linear transistor operating characteristics is substantially eliminated. An input signal is coupled to the base of a first transistor connected in an emitter follower configuration with the signal formed at the emitter of the first transistor coupled to the base of a second transistor. Currents are supplied to the first and second transistors by a current mirror circuit in such a manner that a ratio of the current supplied to the first transistor to the current supplied to the second transistor is made constant. An output signal is produced in response to current variations in a transistor of the current mirror circuit which supplies current to the second transistor.
A current gain stage with low voltage drop usable in place of a Darlington's current gain stage is described. This stage maintains the precision characteristics of the output current value, though presenting a lower voltage drop. The stage is formed by connecting the collector of the input transistor (driver) to a current mirror, the output current of which is added to the output current of the gain stage for maintaining the high precision.
A simple high speed precision transconductance amplifier circuit having a low offset. The circuit uses as an input stage two substantially identical transistors of a first conductivity type connected in series so as to have the same current there through, neglecting base currents. A second stage uses two substantially identical transistors of a second conductivity type connected in series, with the output of the amplifier being a current mirrored from the second stage. The offset is maintained low by maintaining the V.sub.BE of the transistors in the two stages substantially identical by connecting together the base and collector of one of the transistors in one stage and coupling the resulting V.sub.BE of the transistor so coupled to one of the transistors of opposite conductivity type in the other stage. Various embodiments and variations are disclosed.
An amplifier circuit comprising a basic amplifier which includes a first and a second transistor of opposite type in which the emitter terminal of the first transistor is connected to the input of the second transistor, and in which the collector terminal of the first transistor is connected to the emitter terminal of the second transistor to form a first current summing point, and a current mirror circuit connected to the first and second transistors to provide substantially equal collector current in each of the first and second transistors. The amplifier circuit includes a current source connected to said first current summing point to control the DC bias point of the first and second transistors. The amplifier may be adapted to a differential configuration using two basic amplifier circuits.
