TIP2955 Single Power Supply Circuit
This entry was posted on Wednesday, September 5th, 2007 at ten:13 pm and it is filed under Power supply. This circuit makes use of a PNP Energy Transistor TIP2955, it is possible to use another based on your current and voltage requirement. Have a look at R2 a 10 Ohm resistor, once the existing within your load to the power supply is much less than 70mA the voltage across R2 is less than 10E * 70mA = 700mV correct. The base emitter junction of Q1 might be biased or turned on about 700mV, less than 700mV the transistor just does absolutely nothing.
Once the existing in your load goes above 70mA the voltage across R2 goes over 700mV and a smaller base existing Ib flows from emitter to base of Q1 turning about the transistor. Now a collector existing Ic flows from emitter to collector and then to your load supplying the excess desire. The Ic = Ib * hfe exactly where hfe or beta will be the DC acquire value.
Some transistors could have only AC acquire specified which can be lower than DC acquire. TIP2955 features a gain of twenty so for an Ib of 50mA the Ic will likely be 1 Amp which saves the regulator from heating up or shutting down as the primary current flows thru the transistor. Q1 needs to be supplied having a good heatsink.