Friday, August 28, 2020

Using an ohmmeter and resistor to ID a transistor pins

If you need to ID a transistor's leads you can use an ohmmeter to find the lead that shows continuity to the other two leads. Then what?

For sim to work I must have a ground reference so I grounded one side of the battery. The battery and resistor represent an ohmmeter. This meter would have a 1ma movement and is reading full scale or zero ohms.
When connected across the emmiter and base I read the junction forward bias resistance.
I also get a forward junction reading between the base and collector.
The emmitter collector reading is very high.
connecting the resistor between the base and emitter and base produces no current flow or a high resistance.
When the resistor is placed between the base and collector we see transistor action. The high current represents a low resistance reading on the meter. We have proved the transistor pinout and that it will produce a gain.
Placing the resistor from emitter to collector will produce a reading representing the 1k resistor, in this case .6ma. the previous .76ma represented a lower reading. So to repeat the meter reads lower than the 1k resistor proves the transistor connection and function.
In summary connect one metter lead to a pin and check between the other 2. Find the pin that is common when reading between the other 2. This is the base. Conect the meter across the other 2 pins and use the resistor to locate the collector. Simple?

No comments:

Post a Comment