Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [pnp]

A type of bipolar transistor comprised of p-type semiconductor in contact with n-type semiconductor which in turn is in contact with a p-type semiconductor -> thus PNP. The transistor has three terminals, the Emitter, Base and the Collector. Current injected into the base controls the flow of current from Emitter to Collector enabling amplification and switching.

424 questions
29
votes
7 answers

What's the purpose of these two diodes in this circuit?

What's to point of using these two diodes? Can't you just replace them with a resistor?
Michael Koeppen
  • 438
  • 1
  • 5
  • 7
27
votes
3 answers

Why use two transistors driving LEDs when one would work?

Recently received a small PCB from China with a simple LED driving setup (12v input). I spent some time probing it out and reverse engineered this schematic; I'm trying to understand why they designed it so that this uses 2 transistors (granted my…
VindolandaHand
  • 273
  • 3
  • 5
17
votes
3 answers

Why NPN and PNP in parallel in this distortion pedal circuit?

I've come across a guitar pedal circuit called a "Tube Sound Overdrive". The schematic is shown below. It looks like a typical common emitter transistor circuit with an adjustable bias (RV1), except there are two transistors, NPN and PNP in…
Dave H.
  • 510
  • 3
  • 12
17
votes
6 answers

Diode connected BJT instead of a diode

I have read wikipedia and other websites regarding the purpose of a diode connected BJT, but I am not clear on where should we use a diode connected BJT. Where is a diode connected BJT used? Like, in what type of requirements do we need to use a…
user220456
13
votes
1 answer

Can the Common Emmiter Amplifier use a PNP Transistor instead?

This is a simple Class A amplifier using an NPN transistor: Is there a way this can use a PNP transistor, instead (with only 0V and +Vcc, not 0V and -Vcc)? Why or why not?
Ehryk
  • 1,141
  • 5
  • 16
  • 28
12
votes
8 answers

Sinking and sourcing current

I have been reading that NPN transistors are sinking and PNP are sourcing devices. I do not really understand this concept. It says current source device connects load to Vcc and current sinking device connects to ground (low voltage). So does…
Abhishek
  • 153
  • 1
  • 2
  • 4
12
votes
3 answers

What's the difference between NPN and PNP transistors?

Suppose that I know how an NPN transistor works. How different is a PNP transistor? What are the operational differences between a PNP and a NPN?
Denilson Sá Maia
  • 773
  • 2
  • 7
  • 14
9
votes
4 answers

Can I use a PNP Transistor with an Electret Microphone to get an non-inverting output for my Arduino?

I'm looking to simply read the generic sound level from an Electret Microphone. I've seen a number of schematics with NPN transistors, that will provide an inverted output (~5V when quiet, ~0V when loud, linear operation in between). Here's an…
Ehryk
  • 1,141
  • 5
  • 16
  • 28
9
votes
3 answers

How can I convert a PNP to NPN transistor?

I have a circuit which requires a PNP transistor. I only have an NPN transistor. Is there a way to convert one to the other given that they have the same characteristics (apart from the npn/pnp part?) And for others after me... can the reverse also…
Toad
  • 235
  • 1
  • 3
  • 6
9
votes
2 answers

Can someone explain this microcontroller ADC interface (for reading solar panel voltage)?

I am trying to understand the functionality of a circuit found in TIDA-00121 (you can download the design file from here) I assume that this has to do with the fact that the PV is not directly tied to ground (reverse current mosfet may be turned…
fhlb
  • 1,440
  • 3
  • 15
  • 28
9
votes
2 answers

Is one circuit better than the other to drive the PNP transistor?

Of the two circuits, would you prefer one over the other?
lyassa
  • 937
  • 3
  • 8
  • 20
8
votes
4 answers

How do I check a BJT transistor if it is still functional?

Is there a simple method to do a sanity check on a bipolar junction transistor whether it is still functional or defective? simulate this circuit – Schematic created using CircuitLab Say for example I have a circuit that used to function, and I…
jippie
  • 33,033
  • 16
  • 93
  • 160
8
votes
4 answers

How can I make my PNP amplifier circuit to turn off faster?

I'm using the following circuit to switch a 24V signal to a PLC. The rising edge is fast and perfect(38 ns) but the falling edge of the signal is not as good(3.5us)! How can I modify this circuit to have faster-falling edges? simulate this circuit…
Masoud
  • 407
  • 4
  • 15
7
votes
2 answers

Slow PNP turn-off time, how to optimize it

I'm multiplexing a pair of Nixie tubes. The high-side control is done with two pairs of transistors, MPSA92 high-voltage PNP to switch the 160V to the tubes, and a BS108 to control the base of the PNP: simulate this circuit – Schematic created…
anrieff
  • 5,199
  • 1
  • 27
  • 46
7
votes
2 answers

Why do we assume VGS0 for a mosfet in cuttoff and Vce>0 for a BJT in cutoff?

The devices below are both n polarity devices, the BJT is a NPN and the MOSFET is a NMOS. For the BJT in cut-off, why do we have to assume \$V_{ce}>0\$? For the MOSFET in cut-off, why do we have to assume \$V_{GS}…
pyler
  • 367
  • 3
  • 7
  • 18
1
2 3
…
28 29