transistors - How to invert a digital signal - Electrical Engineering ...
WEBBTW, a PNP is an option, but more often an NPN will be used. edit (re your comment) If the input signal is high there will flow current through R2 and the transistor's base-emitter junction (base, not gate). This current will be amplified, and the collector current through R1 will cause a voltage drop so that the output will be low.
Choosing the right transistor for a switching circuit
WEBWhen choosing the right transistor for this job, first I'll eliminate the PNP transistors. They're a bit more complicated to use in your case. As you said, for a PNP transistor, active high becomes active low, meaning the transistor will switch on when you apply 0V from your Arduino, but it won't switch off when you apply 5V from the Arduino.
npn - Sinking and sourcing current - Electrical Engineering Stack …
WEBJul 2, 2013 · But, that's not the only way to use a transistor. For example: simulate this circuit – Schematic created using CircuitLab. This configuration is called common collector or emitter follower. Now the NPN is sourcing, and the PNP is sinking. So, sourcing or sinking doesn't really have much to do with the type of transistor, but rather what it's ...
bjt - How do I saturate an NPN transistor? - Electrical Engineering ...
WEBApr 15, 2011 · A transistor goes into saturation when both the base-emitter and base-collector junctions are forward biased, basically. So if the collector voltage drops below the base voltage, and the emitter voltage is below the base voltage, then the transistor is in saturation. Consider this Common Emitter Amplifier circuit.
How do I know if which leg is the emitter or the collector?
WEBDec 6, 2011 · \$\begingroup\$ Off the cuff - for jellybean transistors I almost invariably use BC337 (NPN) and BC327 (PNP) - both CBE. A transistor selector book woul;d be the easy way to check distributions as they have pinout tables which they assign a letter code to and then show the relevant code for each device.
Which resistor for NPN transistor base?
WEBSo assuming you are happy with 150mA while saturating the transistor to about 1V, you need to push 50 50 into the base. The base voltage will need about 0.7V so the remainder (1.8V - 0.7V) needs to be across the resistor R1. Ohms law tells us that R = . So choose maybe a 360 ohm resistor. If this isn't good enough for your needs look for an N ...
npn - How does the collector emitter relationship work with a ...
WEBThink of the transistor as a valve or faucet. The base is the knob, the water tends to flow from the positive side (storage tank) to the ground (drain), if you follow the normal "current flow" directions.
What (if any) is the leakage current through a NPN (C-E)?
WEBApr 10, 2015 · Make sure there is a resistance from base to emitter when you want the transistor 'off'. Even 1M from base to emitter is enough to make that problem go away- more likely you're driving it from a push-pull output and it will have a very low resistance to keep the ICBO current from being amplified.
How to connect a npn transistor properly? - Electrical Engineering ...
WEBSep 7, 2016 · as said, the load in the emitter branch is detrimental to the gain. driving the base-emitter port with a voltage is a perfect way to destroy the transistor. Either use a current source instead of a voltage source or add a series resistor. If you drive a diode with a forward voltage (2.1V) greater than any available voltage in your system your ...
Changing a 3.3V signal to a 5V signal using a BJT transistor
WEBOct 2, 2016 · The transistor's emitter is pulled to zero volts by that logic source. The transistor's base has no choice but to follow, and is about 0.65v higher. Considerable base current flows (about 1.2 mA). The current ensures that the transistor is heavily saturated.