Many projects that use operational amplifiers, such as the 741, CA3140, etc., need a symmetrical power supply, that is, that provides positive and negative voltages. These sources are special and are just one of them that we describe in this article.
If you have stopped doing some experimenting with operational amplifier for lack of a power source of your own, what about putting one together and leaving it available on your workbench. This power supply, because it is not stabilized, provides a voltage between 9 and 13 V output, serving a good amount of experiments and projects.
The maximum current depends on the transformer. In our case, this current is 500 mA. The monitoring of the operation is done by an LED. In figure 1 we have the complete diagram of the power source.
The arrangement of the components on a terminal strip is shown in figure 2.
On assembly, observe the polarity of the diodes, the electrolytic capacitors and the LED. The primary of the transformer must be in accordance with the local power grid.
For the output we can use a terminal bar with screws or terminals of different colors. Once assembled, measure the voltages at the output of the circuit. Between the extremes we must have between 18 and 24 V and between each end and the center between 9 and 12 V.
Material list:
D1 to D4 - 1N4002 or 1N4004 - silicon diodes
LED- common red LED
R10 - 3.3 k ohm - resistor - orange, orange, red
C1 C2 - 1000 uF x 16 V - electrolytic capacitors
S1- On/Off switch
T1 - Transformer with primary according to the local grif and secondary from 9 + 9 V up to 500 mA
Miscellaneous:
Terminal strip, wires, solder, power cable, etc.
