# Transistor voltage measurement

Discussion in 'General Electronics Discussion' started by Tommy8389, Apr 17, 2017.

1. ### Tommy8389

15
0
Mar 18, 2017
By using voltmeter. How to measure the voltage of collector and emitter. Vbc is the collector voltage and Vbe is the emitter voltage? And how should my voltmeter place? Sorry for the silly question

2. ### Herschel Peeler

401
65
Feb 21, 2016
If you want to measure the voltage between the emitter and the collector that is where the meter leads go. Is your question more complicated? Start with a data sheet for the transistor in question.

3. ### Audioguru

3,041
678
Sep 24, 2016
Vbc is the voltage from the base to the collector.
Vbe is the voltage from the base to the emitter.
Vce is the voltage from the collector to the emitter.

4. ### duke37

5,364
769
Jan 9, 2011
The circuit will have a ground connected to many stages.
Measure the voltage between ground and emitter.
Measure the voltage between ground and base.
Measure the voltage between ground and collector.

Some subtraction will give the voltages required.
With an npn transistor, the voltages relative to ground will rise from emitter to base to collector and there is likely to be about 0.6V emitter/base.

5. ### Tommy8389

15
0
Mar 18, 2017
I placed my voltmeter's positive at the base and the negative at collector. When the transistor is "OFF". I get negative voltage (-0.78v). When the transistor is "ON". The voltage is 0.72v. can you explain for me why? Or i placing it at wrong polarity? Thanks.

4,411
935
Oct 5, 2014
NPN or PNP?

15
0
Mar 18, 2017
Npn

8. ### Tommy8389

15
0
Mar 18, 2017
Ok thanks guys. I found out why there is a negative voltage occured when transistor is off. After i read through the cut-off mode.

9. ### BobK

7,682
1,686
Jan 5, 2010
Why are you measuring from the collector to the base? The more useful measurements are from the emitter to the base and from the emitter to the collector.

Bob

10. ### Audioguru

3,041
678
Sep 24, 2016
We do not have a clue about your transistor circuit because you did not attach its schematic to this thread. The schematic will show the part number of the transistor, the supply voltage and the resistor values. Something (maybe a switch?) on the schematic will turn the transistor on and turn it off. Then we will know all the details.