PNP Transistor – How Does It Work? December 19, 2016 by Øyvind Nydal Dahl 14 Comments The PNP transistor is a mystery to many. But it doesn’t have to be. If you want to design circuits with transistors, it’s really worth knowing about this type of transistor. For example: Want to automatically turn on a light when it gets dark? The PNP transistor will make this easy for you. In my article how transistors work , I explained how a standard NPN transistor works. If you haven’t already, I’d really urge you to read that article first. If you understand the NPN transistor, it will make it easier to understand the PNP transistor. They work pretty much in the same way, with one major difference: The currents in the PNP transistor flow in the opposite directions of the currents in the NPN transistor. Note: This topic is much easier with an understanding of current flow and voltages . How PNP Transistors Work ...
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555 Timer - Frequency and Duty Cycle Calculator
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Enter values for R1, R2, and C and press the calculate button to solve for positive time interval (T1) and negative time interval (T2). For example, a 10K resistor (R1) and 100K (R2) and 0.1 uF capacitor will produce output time intervals of 7.62 mS positive (T1) and 6.93 mS negative (T2). The frequency will be about 70 Hz. R1 should be greater than 1K and C should be greater than .0005 uF. Scroll down page for basic 555 information (pinout and two basic circuits). Positive Time Interval (T1) = 0.693 * (R1+R2) * C Negative Time Interval (T2) = 0.693 * R2 * C Frequency = 1.44 / ( (R1+R2+R2) * C) R1 (K Ohms) R2 (K Ohms) C (Microfarads) T1 (Milliseconds) T2 (Milliseconds) Frequency (Kilohertz) The 555 Timer First introduced by the Signetics Corporation as the SE555/NE555 about 1971. Pin connections and functions: (See schematic below for basic circuits) Pin 1 (Ground) - The ground (or common) pin is the most-negative supply potential ...