improved current source

The basic circuit of a current source is shown in figure 1 . The base-to-emitter potential for the source transistor Tl is derived from the `+ 1` power supply terminal through the potential divider Rl, D1, D2. The T 1 collector current is approximately 600 .. . 700 ill" Rz m 1amps where R2 is in ohms. Minor fluctuations in the `+ 1` voltages affect the Tl collector current via the differential,resistance of D 1 and D2.