Author Topic: Identifying SOT23 Component  (Read 1262 times)

0 Members and 1 Guest are viewing this topic.

Offline ChrisGreece52Topic starter

  • Frequent Contributor
  • **
  • Posts: 832
  • Country: gb
  • Electronics Engineer - Tinkerer - Nerd
Identifying SOT23 Component
« on: January 06, 2019, 09:53:56 am »
Hello i am trying to reverse engineer a PCB but i have a problem identifying an SOT23 component.

Given that SOT23 components usually are diodes or transistors i tried measuring the diode voltages to identify the nature of the component.

In the first ic i got the following results

1(+) --> 2(-) Forward Biased Diode 960mV
1(+) --> 3(-) Forward Biased Diode 960mV
3(+) --> 2(-) Forward Biased Diode 960mV

See problem is the third measurement which if it was an NPN transistor it should be open circuit but it displays a forward voltage of 960mV i do not know if the component is busted or not so that is another problem

There is an identical component above (Markings are 493) and i got the readings below from it.
1(+) --> 2(-) Forward Biased Diode 960mV
1(+) --> 3(-) Forward Biased Diode 960mV
3(+) --> 2(-) Open Circuit
Which tells me that it should be an NPN transistor.

Again i am not sure if both components are operational thank you in advance.
 

Offline T3sl4co1l

  • Super Contributor
  • ***
  • Posts: 22436
  • Country: us
  • Expert, Analog Electronics, PCB Layout, EMC
    • Seven Transistor Labs
Re: Identifying SOT23 Component
« Reply #1 on: January 06, 2019, 10:25:26 am »
Is this in circuit or out?

Tim
Seven Transistor Labs, LLC
Electronic design, from concept to prototype.
Bringing a project to life?  Send me a message!
 
The following users thanked this post: exe

Offline ChrisGreece52Topic starter

  • Frequent Contributor
  • **
  • Posts: 832
  • Country: gb
  • Electronics Engineer - Tinkerer - Nerd
Re: Identifying SOT23 Component
« Reply #2 on: January 06, 2019, 10:34:08 am »
Its on the pcb i did not remove it from the circuit. Do you think that is the problem ?
 

Online PA0PBZ

  • Super Contributor
  • ***
  • Posts: 5259
  • Country: nl
Keyboard error: Press F1 to continue.
 
The following users thanked this post: exe

Offline ChrisGreece52Topic starter

  • Frequent Contributor
  • **
  • Posts: 832
  • Country: gb
  • Electronics Engineer - Tinkerer - Nerd
Re: Identifying SOT23 Component
« Reply #4 on: January 06, 2019, 12:28:49 pm »
I found the problem !!! it is not the transistor but that i left it on the board. As i was drawing the schematic i found out that the two transistors are connected together like this.
Where the normal behaving one is the bottom and the one i got the weird measurements from being the top one.
 

Offline Jwillis

  • Super Contributor
  • ***
  • Posts: 1725
  • Country: ca
Re: Identifying SOT23 Component
« Reply #5 on: January 07, 2019, 12:07:15 am »
Glad you figured it out.

But just as a side note SOT23 are not necessarily just transistors.Although still transistors Mosfets come in that package.Other components include Two planar PIN diodes such as   Schottky Diodes & Rectifiers like the BAS70-00 to BAS70-06 which has a Forward voltage of 1000mV. Others include dual and single zener diodes.Even some sensors are in this package.
 

Offline KL27x

  • Super Contributor
  • ***
  • Posts: 4108
  • Country: us
Re: Identifying SOT23 Component
« Reply #6 on: January 07, 2019, 02:23:19 am »
Add voltage regulators/references and voltage detector IC's (as commonly used in li ion battery protection circuitry).
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf