Burr-Brown’s REF200 provides in independent 8-pin DIL package two independent current sources, either of which can supply 100 NA and a 1:1 current. mirror. The pinout of the device is shown in Fig. 1. Note that there are no pins for connecting a supply voltage. The correct operation of the current. sources are, however, guaranteed when the potential across the source is not less than 2.5 V. The average drift with temperature is only 25 p. p.m. K–1. The output impedance is not less than 100 MQ. The operating voltage must not exceed 40 V. The two sources and the mirror make possible a number of configurations, some of which are shown in Fig. 2. That in Fig. 2a is a 50 µA current source whose output voltage may vary between 0 and the positive supply voltage minus 2.5 V. In Fig. 2b, all parts of the IC form a floating 300 current source. Finally, Fig. 2c shows a bi-directional 100 source.