Power Supply Circuits


Dual Supply From Single Battery Source

Dual-voltage power supply is required especially for powering the op-amps and some of the instrumentation amplifiers. A few low-power audio pre-amplifiers also use dual-voltage supply. This circuit provides both +9V as well as -9V supply from a single 9V battery. It consists of timer IC NE555 (IC1), negative-voltage regulator IC 7909 (IC2) and a few […]


Low Power 12V Transformerless Power Supply

Many circuits can be powered directly from the mains with the aid of a series capacitor (C1). The disadvantage of this approach is that usually only one half cycle of the mains wave-form can be used to produce a DC voltage. An obvious solution is to use a bridge rectifier to perform full-wave rectification, which […]


Dual Supply From Single Battery Source

Dual-voltage power supply is required especially for powering the op-amps and some of the instrumentation amplifiers. A few low-power audio pre-amplifiers also use dual-voltage supply. This circuit provides both +9V as well as -9V supply from a single 9V battery. It consists of timer IC NE555 (IC1), negative-voltage regulator IC 7909 (IC2) and a few […]


Power Supply For USB Devices

More and more equipment is sold that runs off internal rechargeable batteries. Although a matching charger is usually supplied in the package, there are also devices that can only be charged via a USB port. That is not surprising in the case of USB MP3 players, which have to ‘dock’ in the PC anyway for […]


Power Supply For USB Devices

More and more equipment is sold that runs off internal rechargeable batteries. Although a matching charger is usually supplied in the package, there are also devices that can only be charged via a USB port. That is not surprising in the case of USB MP3 players, which have to ‘dock’ in the PC anyway for […]


Regulated Power Supply with Stability at 3A

The circuit was designed to build a stable power supply the will provide a regulated voltage from 40 V to 70 V in a 3 A current. 2N3055 – a complementary Silicon Epitaxial-Base planar NPN transistor mounted in Jedec TO-3 metal case for use as power transistor. BD243 – an epitaxial-base Silicon NPN transistor intended […]


Regulated Power Supply with Stability at 3A

The circuit was designed to build a stable power supply the will provide a regulated voltage from 40 V to 70 V in a 3 A current. 2N3055 – a complementary Silicon Epitaxial-Base planar NPN transistor mounted in Jedec TO-3 metal case for use as power transistor. BD243 – an epitaxial-base Silicon NPN transistor intended […]


Triple Power Supply

Inexpensive miniature transformers normally provide one or two secondary voltages, which is sufficient for generating a set of positive and negative supply voltages, such as are needed for operational amplifier circuits. But what can you do if you need an additional voltage that is higher than either of the supply voltages (such as a tuning […]


Triple Power Supply

Inexpensive miniature transformers normally provide one or two secondary voltages, which is sufficient for generating a set of positive and negative supply voltages, such as are needed for operational amplifier circuits. But what can you do if you need an additional voltage that is higher than either of the supply voltages (such as a tuning […]


Ultra Low Drop Linear Voltage Regulator

This circuit is a Mosfet-based linear voltage regulator with a voltage drop of as low as 60mV at 1A. The circuit uses a 15V-0-15V transformer and employs an IRF540 N-channel Mosfet (Q1) to deliver the regulated 12V output. The gate drive voltage required for the Mosfet is generated using a voltage doubler circuit consisting of […]