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Using the BQ24002 from Texas Instruments it  is possible to build a simple and small charger  module for single lithium-ion (Li-ion) cells. The device is available in a SSOP20 package  and so does not require heroic assembly and  soldering skills. Individual cells are becoming available from  the main catalogue suppliers, but a much  cheaper option is to rescue cells from defunct  notebook  batteries.  In  most  cases  only  a  couple of cells are faulty and the others can still look forward to a long and useful life.  A single cell is ideal for any equipment that  needs a 3.3 V power supply, and will generally give a good operating life. The charger  circuit requires a 5 V input, which can readily  be obtained from a USB port or from any 5 V  power supply.   Circuit diagram: Single Lithium Cell Charger Circuit diagram   The  charge  process  begins  with  a  trickle  charge current. When the cell terminal volt-age is sufficiently high the charger switches  to a higher constant ...

Here is a compact low cost FM radio circuit using IC TDA 7000. This circuit is designed as per the data sheet and the result is excellent.Ideal for all category of electronic enthusiasts. Single Chip FM Radio Circuit Diagram The TDA7000 is a monolithic integrated circuit for mono FM portable radios, where a minimum on peripheral components is crucial. The IC TDA 7000 has a Frequency-Locked-Loop system with an intermediate frequency of 70 kHz. The intermediate frequency selectivity is achieved by active RC filters. The only function which needs alignment is the resonant circuit for the oscillator, thus selecting the reception frequency. Spurious reception is avoided by means of a mute circuit, which also eliminates too noisy input signals. Special steps are taken to meet the radiation requirements.  Notes:   For L1 and L2 wind 5 turns of 0.6 mm enameled Copper wire on a 4 mm dia plastic former. For antenna use a 50mm long insulated copper wire. IC TDA 7000 can withstand up...

This is a Simple Single Supply Voltage Regulator Circuit Diagram. The circuit uses a CA3140 BiMOS op amp capable of supplying a regulated output that can be adjusted from essentially 0 to 24 volts. The circuit is fully regulated. Simple Single Supply Voltage Regulator Circuit Diagram

Many modern electronic devices and micro-controller based circuits need a 5 V or 3.3 V power  supply. It is important  that  these voltages are constant and so a regulator of some kind is essential, including in battery powered devices. The simplest approach is to select a (perhaps rechargeable) battery whose voltage is rather higher than that required by the circuit and use an ordinary  linear voltage regulator. Unfortunately this solution is rather wasteful of precious energy and space: for a 5 V circuit at least six NiCd or NiMH cells would be required. Both these disadvantages can be tackled using a little modern electronics. A good way to minimise energy losses is to use a switching regulator, and if we use a regulator with a step-up topology then we can simultaneously reduce the number of cells needed to power the circuit. Fortunately it is not too difficult to design a step-up converter suitable for use in portable equipment as the semi-conductor manufacturers...

This Electronic Project of Single Ltc Power Supply circuit is very low cost, and high efficiency battery-powered applications.  One LTC 1149 synchronous switching regulator can deliver both 3.3- arid 5-V outputs.  Single Ltc Power Supply Circuit Diagram: The design`s simplicity, low cost, and high efficiency make it a strong contender for portable, battery-powered applications. The circuit described accepts input voltages from 8 to 24 V, to power any combination of 3.3-V and 5-V loads totalling 17 W or less. For input voltages in the 8-V to 16-V range, the LTC1148 may be used, reducing both quiescent current and cost.