Originally Posted by jrz126

Originally Posted by Ron H

Jrz126, this is a push-pull emitter follower, but it only works well for analog signals if you keep the input signal range well within the collector supply voltages (+/-5v in this case). It will have significant crossover distortion unless it is embedded in a feedback loop containing a fast slew rate op amp. As a stand-alone circuit, it is good for driving heavy loads with digital or switching inputs.

In my circuits lab, we had a +/- 15V on the ends of the transistors, so I guess it worked out ok. the way we did it was, we had a D/A converter hooked to the audio out of a cd player, then we converted it back. It was only 8-bit D/A, so it didnt sound that good anyways.

but anyhoo, when Vi is equal to -10V, would the PNP transistor be in saturation mode?

Re-read my post.

If Vcb (or Vbc I cant remember which I used. but I did use the correct one for my hw.) <(-0.4V) then it is in saturation mode.
IIRC my Vcb for the -5V case was -0.38V, since it was very close to -0.4, I just assumed the -10V case was in saturation (I only had 10 minutes before i had to turn it in so I couldnt double check it). I calculated my forced beta (Ic/Ib) to be 99 and the actual beta was 100


Samcheeta, thanks for your help with that. I found an example of the circuit in my pillow :lol: , so I noticed that the NPN was cut off. Is that simulator program free/any good? I think it might come in handy.
Could Sam's simulation be messed up since the beta wasnt specified?

SwitcherCAD III is free and uncastrated, with no time or size limits. You do need to have some previous experience with spice, or be very good at using the help files.
Not specifying beta usually won't cause a problem when simulating with generic transistors, because most simulators default to a simple model which has beta as one of the parameters. For example, SwitcherCAD III uses beta=100 for the generic NPN.

Jeff, I see you are majoring in procrastinology. I majored in Pinochle my first two semesters at San Jose State, and came to the realization that it was too tough, and I was gonna flunk out if I didn't change my major. That's how I became an engineer.

Originally Posted by jrz126

Samcheeta, thanks for your help with that. I found an example of the circuit in my pillow

:lol: i told you it was a good book!!!!

the simulator i use is Multisim 7. you can download a demo version of Multisim 7 from http://www.electronicsworkbench.com but there is one problem with the demo version. you cant save any file and the libraries have only a few parts.

i also have SwitcherCAD III but i havent used it much. you can download the free version of SwitcherCAD III from Linear Technology's website http://www.linear.com

ive said it a number of times that i personally that much in simulators. a hands-on approach is much better. and most of the work we do in the lab is on a breadboard. but when im in my house i dont have all the components at hand. so just to get an idea of the circuit i simulate it on Multisim.

i agree with the calculations made by Ron H. maybe there is something i dont know about Multisim that resulted in the wrong calculations. like some days back i started a discussion about opamp supply current. when i simulated a simple circuit in Multisim it seemed as if Multisim wasnt obeying Kirchoff's current law. but then Optikon pointed out that there would be some current in the node 0 of the opamp model which multisim is using. so there must be something simillar here.

i know that this is a very old topic that i am replying to. but today i was looking at a simillar circuit (the one in the book Microelectronic circuits which jrz pointed out). i remembered that multisim gave me wrong results for this circuit. so i simulated this circuit again on multisim and saw the output. but i was still getting wrong values. and there were really strange things happening with other circuits i had. so i did a reinstall of Multisim and voila!!!!!! everything works right now. the following are the results that i got after simulating this circuit in multisim. the results are simillar to those predicted by Ron_H

so just to set the record straight here are the results that i got