Monolithically integrated current source with a high output resistance and their use in a two wire / two-wire - by means of gear circuit

摘要

The source supplies a constant output current dependent on a reference current and comprises a first stage having separate transistors carrying the reference and output currents. A second stage is connected to the first in such a way that the output current transistor is base-coupled. The second stage is pref. a third transistor in the emitter circuit of the first and a fourth transistor in the emitter circuit of the second, whereby the emitters of the second and third transistors are connected to a suitable terminal of the reference current source. A high impedance output is produced even at relatively high currents in the order of 10 mA.