emavil
Member level 2
Hi,
Can any one help me the proper way of computing the gain of a bipolar transistor. Let's say the 2N2222 or BC547. I use them to control the Common Cathode 7-segments. I saw lots of circuit examples on the net multiplexing 7-segments in digital clock circuits. Im a hobbyist of PIC Microcontroller and I have a little background on the engineering perspective of electronics. I'm using a regulated power source (+5vDC) generated by L7805CT regulator. The collector is connected to the Common Cathode of a 7-segment. The Emitter is connected to ground. And the base is filtered with 1K resistor going to the I/O pin of PIC.
My question is, what is the difference of changing the base transistor to 22K, some circuits, they use 470Ohms? What is the effect with respect to gain of the transistor if the resistor in the base of the transistor is small or big.
I also read statements like CONSTANT CURRENT source especially driving LEDs and 7-segments. What is it:?:
Can any one help me the proper way of computing the gain of a bipolar transistor. Let's say the 2N2222 or BC547. I use them to control the Common Cathode 7-segments. I saw lots of circuit examples on the net multiplexing 7-segments in digital clock circuits. Im a hobbyist of PIC Microcontroller and I have a little background on the engineering perspective of electronics. I'm using a regulated power source (+5vDC) generated by L7805CT regulator. The collector is connected to the Common Cathode of a 7-segment. The Emitter is connected to ground. And the base is filtered with 1K resistor going to the I/O pin of PIC.
My question is, what is the difference of changing the base transistor to 22K, some circuits, they use 470Ohms? What is the effect with respect to gain of the transistor if the resistor in the base of the transistor is small or big.
I also read statements like CONSTANT CURRENT source especially driving LEDs and 7-segments. What is it:?: