Circuit arrangement for a controllable current source

摘要

The invention relates to a controllable current source, the output current of which follows a control voltage up to a maximum amount, stays at this value when the control voltage is increased further and, if nothing is connected to the control voltage input, assumes a predeterminable value below or equal to the maximum amount, preferably in integrated technology, for example for brightness or volume controls. The object of the invention is the creation of a controllable current source with intermediate-value adjustment with a high-impedance circuit connected to the input and a maximum current, even when the control voltage is exceeded which corresponds to the maximum current. According to the invention, this object is achieved by the fact that the current balancing circuit precedes the base of the input transistor via one or several diodes, the resistance of the current balancing circuit being dimensioned in such a manner that the base current of T2, multiplied by the current gain factor, is greater than the base current of the input transistor.