Controllable current source for earthed load - has preamplifier and transistor power amplifier, each with separate supply source

摘要

The current source has a preamplifier to which a control voltage is applied, and a following transistor power amplifier connected to an earthed supply energy source. The earthed load is connected to the power amplifier (7) output through a resistor (B). A further supply energy source is provided for the preamplifier (1). This supply source frame point is connected directly to the power amplifier (7) output, and the supply voltage of the first source depends on its load and the current through the load. A feedback lead (17) couples back from the output of the power amplifier (7) to the input load (3) of the preamplifier.