Battery powered Headphone Amplifier

Low distortion Class-B circuitry 6V Battery Supply

Some enthusiasts of High Fidelity headphone listening want the utilization of battery energyed headphone amplifiers, not just for transportable gadgets but additionally for home \"table\" softwares. This design is intended to fulfil their needs and its topology is derived from the Portable Headphone Amplifier that contains an NPN/PNP compound pair emitter follower output stage. An superior output using functionality is achieveed via making this a push-pull Class-B association. Output energy can reach one hundredmW RMS into a 16 Ohm load at 6V supply with low standing and mean present consumption, allowing lengthy battery duration. The single voltage gain stage permits the easy implementation of a shunt-feedback circuitry giving superb frequency steadiness.

Circuit diagram :

Battery-powered Headphone Amplifier Circuit diagram

Notes:

• For a Stereo model of this circuit, all parts should be doubled aside from P1, SW1, J2 and B1.
• Before setting quiescent current rotate the volume regulate P1 to the minimum, Trimmer R6 to most resistance and Trimmer R3 to in regards to the middle of its shuttle.
• Connect an acceptable headphone set or, better, a 33 Ohm 1/2W resistor to the amplifier output.
• Switch on the provision and measure the battery voltage with a Multimeter set to about 10Vdc fsd.
• Connect the Multimeter throughout the positive end of C4 and the poor floor.
• Rotate R3 with a view to learn on the Multimeter show precisely half of of the battery voltage in the past measured.
• Switch off the availability, disconnect the Multimeter and reconnect it, set to measure about 10mA fsd, in sequence to the certain supply of the amplifier.
• Switch on the provide and rotate R6 slowly except a studying of about 3mA is displayed.
• Check once more the voltage on the positive finish of C4 and learnjust R3 if essential.
• Wait about quarter-hour, watch if the present is various and readjust if important.
• Those fortunate sufficient to achieve an oscilloscope and a 1KHz sine wave generator, can power the amplifier to the utmost output power and alter R3 with a goal to get hold of a symmetrical clipping of the sine wave showed.

Technical data:

Output power (1KHz sinewave):
    16 Ohm: 100mW RMS
    32 Ohm: 60mW RMS
    sixty four Ohm: 35mW RMS
    100 Ohm: 22.5mW RMS
    300 Ohm: eight.5mW RMS
Sensitivity:
    160mV enter for 1V RMS output into 32 Ohm load (31mW)
    200mV input for 1.27V RMS output into 32 Ohm load (50mW)
Frequency response @ 1V RMS:
    flat from 45Hz to 20KHz, -1dB @ 35Hz, -2dB @ 24Hz
Total harmonic distortion into 16 Ohm load @ 1KHz:
    1V RMS (62mW) zero.015% 1.27V RMS (onset of clipping, a hundredmW) 0.04%
Total harmonic distortion into 16 Ohm load @ 10KHz:
    1V RMS (62mW) 0.05% 1.27V RMS (onset of clipping, one hundredmW) 0.1%
Unconditionally secure on capacitive loads

Source : red circuits

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Battery Powered Night Lamp

Ultra-low current drawing 1.5V battery supply

This circuit is usable as a Night Lamp when a wall mains socket is not available to plug-in an ever running small neon lamp device. In order to ensure minimum battery consumption, one 1.5V cell is used, and a simple voltage doubler drives a pulsating ultra-bright LED: current drawing is less than 500µA. An optional Photo resistor will switch-off the circuit in daylight or when room lamps illuminate, allowing further current economy. 

 
This device will run for about 3 months continuously on an ordinary AA sized cell or for around 6 months on an alkaline type cell but, adding the Photo resistor circuitry, running time will be doubled or, very likely, triplicated.

Battery-Powered Night Lamp Circuit diagram :

 

Parts:

R1,R2___________1M   1/4W Resistors
R3_____________47K   1/4W Resistor (optional: see Notes)
R4____________Photo resistor (any type, optional: see Notes)

C1____________100nF  63V Polyester Capacitor
C2____________220µF  25V Electrolytic Capacitor

D1______________LED  Red 10mm. Ultra-bright (see Notes)
D2___________1N5819  40V 1A Schottky-barrier Diode (see Notes)

IC1____________7555 or TS555CN CMos Timer IC

B1_____________1.5V Battery (AA or AAA cell etc.)

Circuit operation:

IC1 generates a square wave at about 4Hz frequency. C2 & D2 form a voltage doubler, necessary to raise the battery voltage to a peak value able to drive the LED.

Notes:

• IC1 must be a CMos type: only these devices can safely operate at 1.5V supply or less.
• If you are not needing Photo resistor operation, omit R3 & R4 and connect pin 4 of IC1 to positive supply.
• Ordinary LEDs can be used, but light intensity will be poor.
• An ordinary 1N4148 type diode can be used instead of the 1N5819 Schottky-barrier type diode, but LED intensity will be reduced due to the higher voltage drop.
• Any Schottky-barrier type diode can be used in place of the 1N5819, e.g. the BAT46, rated @ 100V 150mA.

Source :  http://www.ecircuitslab.com/2011/06/battery-powered-night-lamp-circuit.html

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