Electronics > Beginners
Common Collector Question
GerryR:
The circuit you show is a very basic follower circuit. If you bias it using a divider and keep Rb about 1/10 of beta Re (~10k), I don't think you will have an oscillation problem. Just a guess.
Jwillis:
Did you check that your power supplies are reading accurate . I did the same experiment and got a value 1.94 V at your test point until I checked that the supply .I found out that the readings on the supply are a bit out . I adjusted with an accurate multi meter and got a value of 1.91V at the test point.This gave a a voltage drop of 0.6 V .
Rechecked with two other meters and got different test results until I adjusted the supply with each individual meter.
With a simple circuit like this I have doubts its an osculation issue but more likely a voltage reading issue.
Like most people I can't afford to by the most accurate instruments available and most less expensive ones are always a bit out even the readings on power supplies can be out.
Check your supply voltage with the multi meter your using to check your test point. Check your components.
Although simulators are good for putting together a circuit they apply data based on whats been input-ed and will almost always give values different from real world applications.
Data sheets values are based on an average of several tests but don't reflect the real world values of a particular component.
Simulators are based on those data sheets. So you have to allow for a degree of error when you use the components in the real world.
Although bread boards do exhibit a parasitic capacitance it tends to be very small. I've tested my boards and found the capacitance to be less than a couple picofarads. This may be a problem for some projects like RF or high frequency experiments but not for simple linear tests like this one
I myself wouldn't worry a lot about small errors to what is expected because this will occur .
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