Linearly adjustable transistor amplifier - has mirror circuit forming with transistor comparator extending voltage drop

摘要

The amplifier has a reference point at the collector resistor connected to the supply source positive terminal and controlled by a first transistor in accordance with collector current of a second transistor controlled in the opposite sense. The voltage drop across an impedance in the second transistor collector circuit is transmitted to the reference point by a third emitter follower. The base-emitter voltage of the latter is balanced by a further transistor. The voltage drop across the impedance (19) is applied to a fourth transistor (4) which forms with a current mirror circuit (26-28) a comparator which transmits to the third transistor (3) the base voltage of the fourth transistor (4).