DC Regulated power supply Using 741 Op Amp IC And 2N3055 Power Transistor
The voltage regulated power supply provides an adjustable voltage output at a load current up to 1A. The supply has a built-in overload protection.
|D1||3 Amp Diode|
|D2||3 Amp Diode|
|D3||1 Amp Diode|
|D4||6.8V 500mA Zener Diode|
|D5||6.8V 500mA Zener Diode|
|T1||2N1481 or D313 or 2SC1061|
|TR1||SEC 15V, 2AMP|
Rectifier diodes D1 and D2 along with capacitor C1 provide the main unregulated supply. D3, C2, R8 and zener diode provide a negative voltage supply for the 741. The non-inverting input terminal of 741 is given a stable voltage by R3 which is the control to set the output. A fraction of the regulated output is fed back via R4 and R5 to the inverting input terminal. The operational amplifier adjusts its output voltage so as to keep the voltage at the input terminals equal. Thus the output gets regulated. The output of 741 is amplified by a compound emitter follower T1 and T2.
All the current flows through R6. If the load current exceeds 1A, the voltage drop across R6 exceeds 0.6 volts and T3 starts conducting. This bypasses the supply to T1 and T2 and the regulating action stops. The output voltage therefore starts falling when the load current exceeds 1A. Any of the output terminals can be grounded to get a positive or a negative voltage with respect to the ground.
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