Many electronics circuits and projects for learning in simple ways.

9V negative power supply circuit, low ripple

This is a simple 9V negative power supply circuit that low ripple unregulated circuit.  It has an output current of about 1A max. Often we make many positive voltage supplies.  But we sometimes need to make negative power circuit. See in the circuit below.

9V Negative power supply units


Simple negative power supply circuit

Both circuits have an opposite polarity supply, Diodes, Electrolytic capacitors. And in positive we use NPN transistor – TIP31, but in negative we use PNP transistor-TIP42.

The difference another one, it doesn’t have a Zener diode. Since it is an unregulated supply circuit.

But it is special, low ripple, low noise, and a constant voltage at 9V.

While unregulated circuit has too much a load current. It also has too much ripple or a noise.

In general, We will reduce the ripple by adding the large capacitor. It is a nice way.

Also a good idea, we use the gyrator effect.

The input capacitor C2 at the base of a transistor. It makes a stable voltage for the current gain of the transistor.

If transistor has a lot of gains such a 50 it can reduce a rate of ripple to low down.
The transistor will increase a high current to the output at its emitter.

The circuit is interesting because it is a smaller, cheap. We can this circuit is a high quality smoothed supply for a lot of loads, DC motor, Coils, Power lamps and more.

The output is full at 1A. Because of:

  • a transformer is 1A to 2A, 6.3V SEC.
  • And C1-1000uF 25V Electrolytic capacitor, you can change with 2200uF 25V, or add another one in parallel.

While the transistor is working, will have too hot. We should mount the big size heatsink. And add a fuse to protect the circuit from overload current.

But you want to builds easily circuit, you may use IC-7909 DC regulators

Keep reading: ‘9V Regulated circuits using transistors’ »

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Close Menu