universal power supply

4-06 — elektor april 1981 universal power supply with respect to the "—" input, so that the two outputs will be low. This prevents D2 and D3 from lighting and this time it is Dl that lights to indicate that TUT2 is the "better" choice. The circuit diagram and the printed circuit board Figure 2 shows the complete circuit diagram of the tester. All it consists of is a single IC, type TL 084, which contains four FET opamps. Schmitt trigger Al and the integrator built up around A2 combine to form a simple triangular wave generator. This provides the transistors under test with an input voltage. The other two opamps (A3 and A4) act as comparators and it is their outputs which control the LED jndi- cations, Dl ... D3. A closer look at the conglomeration of resistors in the collector leads of the two TUTs will explain why we used a simplified version of the circuit to clarify the principle. The final circuit looks much more complicated, as a tandem pot (Pl) has been added to preset t...