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28 Threads found on Npn Logic
You should not use a npn transistor, but a PNP instead.
Check the input high threshold of the micro, the npn circuit will lose Vbe between input voltage and the output so it may not reach logic 1 anyway. With the top circuit, you might be able to replace it all with a Schottky diode, cathode to the signal source side. For the bottom circuit, consider removing the transistor and 10K resistor the connecti
You are trying to design a high-side or "source" driver. UDN2981 or 2984 is a single chip solution for the problem. A discrete solution would use high-side PNP respectively PMOS switches and a level shifter circuit to control it by ground referenced 5V logic. E.g. a npn transistor and a few resistors.
I have attched a image file for transistor logic... will this logic work? Typical setup for npn biasing. Output is taken at collector sensor (or touch contacts) can be one or the other side of the potentiometer. Detach the potentiometer
When using common-cathode 7-segment display we use npn transistors with the emitter connected to GND and collector to the 7-segment display. In contrast when using common-anode 7-segment display we use PNP transistors with the emitter connected to +5V and the collector to the 7-segmnet display. In both cases the emitter is connected to a fixe
No, you will have to use another mosfet/npn transistor.
You can just translate the digital signal from 5V to 24V using an npn transistor for example. It is quite simple. Unless you have other constraint, a transistor would be good enough for most voltage translation function. The follow is a link which explain in simple illustration how a transistor can be use for converting the voltage logic that you n
will this circuit work? All npn transistor switching circuits I have seen switch higher voltages from lower voltages (at base). Here, I need to switch 3.3V with 12V. i.e When no voltage at base Vout should be high (3.3V) and when 12V at base Vout should be Low (0V). Thanks mahenk
Depends on the application. In general I prefer the npn because it can be driven directly by a logic output. And the VCC of the relay can be higher than the logic level. For example you can control a 12v, 24v (or more) relay with a TTL output. The PNP is useful when a High side driver is required. It needs an extra transistor or an Open (...)
use an npn transistor (bjt) with a base resistor to invert the logic. something like this --
Hi Kishore680, yes it is possible, but the turn off speed of transistor will be much lower. A simple circuit is shown in below link. R4 should stay there, because it supplies Vbe and discharging path for different timings (i.e. ON/OFF). Juts R3 is rplaced by diodes. It helps to adjust different threshold levels. Otherwise would npn always stay ON
Use an npn transistor to drive the relay. Send a logic 1 to the base of the transistor to turn on the transistor and hence drive the relay. Send a logic 0 to the base of the transistor to turn off the transistor. Use a current limiting resistor between the transistor base and the microcontroller pin. Make sure you configure that pin as an (...)
Your assumption is basically correct. The terms are describing the output polarity of sensors with digital logic output based on an output transistor in common emitter configuration. "PNP" refers to positive supply switching, "npn" to ground switching. "PNP" is the output type needed to interface with industry standard PLCs.
a simpler solution is add another open collector npn in parallel and call its Base Input (+R) = Disable, the pull up 10K is fine for CMOS will go high only when Disable is low and left input is low
Hi all I want to use npn (BF199) to convert the sin wave from my oscillator to a digital wave ( of 2V PK-Pk). At the moment I am getting something close to digital wave but with 1.6 V P-P. The base of the npn has a sin wave at 124 KHz with 800mV p-p. The collector is connected to a voltage divider. The emitter goes to ground. Any idea
I think you can use the following circuit, any npn and PNP would do the job 68509 Alex
Dear all If uses a single npn transistor to drive LEDs, can anyone tell me what is the advantage and disadvantage to put those LEDs at collector (graph A) or at emitter terminals (graph B)? Thanks Regards
If you don't want to face issues while driving a switch from a 3.3V logic consider an inverter based on an npn (or N-channel MOSFET) followed by P-channel MOSFET (or PNP) working as a high-side switch .. See fig.3 at: IanP :wink:
The purpose of this circuit is for shifting the voltage level from logic level to +1.5V and -3V. When the base of npn receives -7V: npn is off and PNP is on, the output is around +7V. But when the base of npn receives -2V: npn is on and PNP is off, the output is around +12V. Where this +12V comes (...)
First measure what logic you get as an output. HI or low, then you may decide wether to use npn or PNP general purpose transistors to amplify the output. Any ways, in case of confusion, posting your present schematic will fetch better answers. Cheers