These are 15v dual power supply circuit for a preamplifier. If you finish a Preamplifier with tone control using op-amp completely. But they need a three-terminal power supply, +15V, OV, -15V at 0.5A current. So, you have to build 15V Dual Rail power supply schematic with PCB. There are 3 circuit ideas for you choose as necessary work.
Dual 15V Power supply Schematic, 1A with IC-7815, IC-7915
Now, most people normally use IC-7815 & 7915 to this. Why use them?
- Cheap—they are in the 78xx and 79xx series. So cheap!
- Easy to use and Small—with 3 terminal pins input, ground, and output only.
- Great quality—the voltage regulator IC can keep the constant voltage at output and overload protection
How this Circuit Works
See in the circuit below.
To begin with, the transformer should have a primary rating of 240V/220V for Europe or 120V for North America. The center tapped secondary coil should be rated about 15V to 18V at 1 A or higher.
This 15V Dual rail output power supply is powered by the transformer. The 220V AC mains comes to the primary. Then, providing into 3 rail voltage, 15VAC, 15VAC and 0V of the secondary.
After that, the current flows through a full-wave bridge rectifier. Which they consist of four 1A diodes with a 100 PIV rating. And then, the electrical current flow to both C1, C2 – 2,200 uF/35V capacitors to completely filter to providing the dual rail, +21VDC, OV, -21VDC.
The C3, C4- 0.22uF capacitors are used to filter noise signal in DC voltage.
Then, DC voltage comes to Both DC Voltage Regulator IC.
- LM7815 keeps the 15V positive voltage output.
- LM7915 controls -15V fixed negative voltage output.
Each IC can give a maximum output current of about 0.5A.
For more Capacitors C5, C6, C7, C8 are used to smooth and clean noise in DC output.
Other detail both of the circuit.
How to build it
This circuit is easy. First of all, you should get parts list.
The components list
|4||D1-D4||1N4001||1A 50V Silicon Diode|
|2||C3,C4||0.22uF 50V||Ceramic capacitors|
|2||C7, C8||0.1uF 50V||Ceramic capacitors|
|1||T1||Transformer 15V CT 15V or 18V CT 18V 0.5A to 1A|
Then, assemble on perforated board or Universal PCB board. as the image below.
And can see video testing circuit.
An application for this type of circuit. It is suitable to be a small regulated bench power supply. Also, you look at second ideas.
15V dual power supply circuit For Preamplifiers
In the previous circuit, use regulator IC. I want to show you another way to build 15v dual power supply circuit for preamplifiers. It also can give a dual-rail output +15V, OV, -15V and maximum current output up to about 1A.
This uses a Zener diode and transistors. So easy to find parts and build easily it. Though very ancient, it still has many uses. Because it is classic and low noise circuit. So it can power to a general preamplifier or pre tone control using op-amp or transistor.
How it works
In the circuit below. It is similar to the previous circuit. They consist of T1, D1, D2, D3, D4, C1, and C2. These components are Unregulated supply section.
- T1—step-down transformer from 220V AC on the primary, and then providing about 18VAC + 18VAC on the secondary
- D1 to D4—full-wave rectifier bridge to convert AC to pulsating voltage DC.
- C1,C2—filter capacitors to smooth DC to a stable DC voltage.
Now, they get +24VDC, OV, -24VDC.
Then, the current comes to a filtering regulator section. They made up of R1,R2,R3,R4,R5,ZD1,ZD2,and Q1,Q2,Q3,Q4.
In positive regulator section(up). the current flows through R1 and ZD1. The Zener Diode keeps the voltage constant across the base of Q1. It is in a common collector. So the voltage of the base equals the voltage of emitter(VE). C4 is filtered any noise it +15V rail.
So, the output is fixed voltage about 15V.
For negative regulator section is similar to positive (different polarity only). They include R2, ZD2, Q3, and C3. So they make -15V fixed voltage output.
This has overcurrent protection with Q2 and Q4 transistors. When a load uses too much current about 1A, both positive and negative rail supply.
Makes a voltage across B-E of Q2, Q4 is high enough to turn on Q2 and Q4 work. When they work, its C-E leg like to be switch on to closes Q1 and Q3 stop.
Thus the output is zero current.
Let’s build 15V transistor Dual supply
At below, here is PCB layout to guidelines to builds this circuit. Hope you fun Dual DC Regulator 15V using C1061 and A761.
The components list
|1||Q1||2SC1061||60V 4A NPN transistor|
|1||Q2||BC548||40V 0.5A NPN transistor|
|1||Q3||2SA671||60V 4A PNP transistor|
|1||Q4||BC558||40V 0.5A PNP transistor|
|4||D1 to D4||1N4007||1000V 1A Diodes|
|2||ZD1,ZD2||15V 1W||Zener diodes|
|2||C1, C4||1,000uF 25V||Electrolytic|
|4||R1 to R4||3.3 ohms||0.5W Resistor|
|1||T1||Transformer 15V CT 15V or 18V CT 18V 1A to 2A|
|***||PCB and more.|
If you want 1A output current. Friends should use transformer 1-2A rating. Both transistor Q1 and Q3 should be installed enough large heatsink.
You can use others transistors. If you cannot get power transistors.
- 2SC1061: TIP41, TIP31, MJE3055, and more NPN transistor 4A 100V rating
- 2SA671: TIP42,TIP32,MJE2955, and more NPN transistor 4A 100V rating
Simple 15 volts dual power supply circuit diagram
This is a very old circuit. It has 3 output voltage terminal are +15V, GND, -15V at maximum 500mA.
Also, it is ideal for a pre-audio amplifier circuit like the integrated circuit LM7815 and LM7915. But sometimes we cannot them but we can use this classic circuit.
How circuit works
When 117VAC (250VAC) is fed to the power cord, the neon-lamp L1 light up, and transformer T1 changes 117VAC to about 28VAC. The bridge D1 to D4 rectifies the AC in DC, next to both capacitors C1, C4 acts as a filter for a smooth DCV. Now we have +33V CT -33V DC unregulated.
Then, the electrical current flow to both 330 ohms series resistor for limit current to the Zener Diodes ZD1, ZD2. They keep the voltage constant across the base of transistors at 15V cause Q1, Q2 works increase high current to the output.
Parts you will need
|4||D1 to D4||1N4007||1000V 1A Diodes|
|2||ZD1,ZD2||15V 1W||Zener Diodes|
|2||C1, C4||500uF 50V||Electrolytic|
|4||R2, R3||330 ohms||0.5W Resistors|
|1||T1||Transformer 18V CT 18V to 25V CT 25V 1A to 2A|
Cannot get parts
If you cannot find both transistors.
You may use Q1-2N4053 = 2N4037 or BD140 pair with
Q2-2N3446 = 2N3053, BD139 instead of them.
You can buy easy and the price is inexpensive. Hope friends have fun the Dual linear regulator +15V -15V Circuit.
I hope you have fun with this Dual DC Regulator 15V using transistors. If you think that This circuit is not good enough. For your work. It is hard to find equipment. You do not have it now. These circuits may be viewed below. It may be appropriate for you.
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