BJT BASED SINE WAVE OSCILLATOR

Thread Starter

Amandeep Singh

Joined May 9, 2009
2
I want to Design a sine wave oscillator using BJT which should generate frequency between 150Hz to 350 KHz and also write the PSpice programme for the same.
Is there anybody who can help me ??
 

CDRIVE

Joined Jul 1, 2008
2,219
What would be really impressive would be to reproduce the Hewlett Packard historic (HP-200A) using FETs and solid state approach to the large variable cap. If my memory is correct, each section of a ganged cap (like the one shown in the photo) were about 365pF max.

http://oak.cats.ohiou.edu/~postr/bapix/HP200C.htm
 

Wendy

Joined Mar 24, 2008
21,840
Anyone remember the 60° oscillator? I remember it from college, each RC leg shifts the frequency 60°, 3X60° is 180°, and since the transistor oscillator shifts the freq another 180° you have positive feedback.

 

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SgtWookie

Joined Jul 17, 2007
22,201
Yeah, it's fun stuff. ;)

Unfortunately, I think our OP forgot to include that it's a homework assignment, and as such, we can't do the work for him - he's got to 'noodle it out' for himself.

Can someone move this thread to the Homework Forum please?
 

CDRIVE

Joined Jul 1, 2008
2,219
Yeah, it's fun stuff. ;)

Unfortunately, I think our OP forgot to include that it's a homework assignment, and as such, we can't do the work for him -
We have the same policy on VB Forums and it's a good one. Somehow I missed the tell tales in his post though.
 

Wendy

Joined Mar 24, 2008
21,840
I left the values off so he could go through the exercise. I figure everyone has seen this oscillator, or will.

We have the same policy on VB Forums and it's a good one. Somehow I missed the tell tales in his post though.
VB Forums?
 

DonQ

Joined May 6, 2009
320
Anyone remember the 60° oscillator?
Yeah. Except I know it as the "phase-shift oscillator". The phase shift doesn't need to be the same at each stage, the oscillator will find the frequency where the combined phase shift totals 180 and go happily on its way.

I think, even with equal value components, the phase shift per stage is not equal because of the parallel paths being different on the different stages, and the loading of the gain component on the last stage. Some manipulation of the values at each stage can make it closer, but "60° oscillator" is probably still optimistic.:D
 

Wendy

Joined Mar 24, 2008
21,840
Yep, but when you teach theory you don't always get into the messy details, those come later. When I was learning this stuff they didn't have SPICE, and the computer we got to use in the electronics class was a PDP brought in a trailer (a big trailer).

Like I said, it's been 30 years. The circuit stuck, even if the name didn't.
 

DonQ

Joined May 6, 2009
320
Like I said, it's been 30 years. The circuit stuck, even if the name didn't.
Best I can remember, I learned of the "Phase shift oscillator" in the fall of 1972! (Don't tell anybody :D). Then, they taught both the tube and the semiconductor versions of circuits.
 

viip

Joined Apr 16, 2009
23
Best I can remember, I learned of the "Phase shift oscillator" in the fall of 1972! (Don't tell anybody :D). Then, they taught both the tube and the semiconductor versions of circuits.
How messy it would be to work with those tubes..These lil opamps chips are the best and cute too:D

And pspice is old thing..why dont you go with simulation tools like multisim..
 

JoeJester

Joined Apr 26, 2005
4,074
multisim.. is a version of "spice". I highly doubt the makers of multisim re-created all the available models for their component list.

Vacuum tubes are not messy ... well, they could be if you grabbed the 21,000 volts and you and/or your body made the mess. :D

Build a phase shift oscillator with multisim. Substitute different OpAmps and see the frequency changes. It's probably as messy as vacuum tubes. :D
 

KL7AJ

Joined Nov 4, 2008
2,208
What would be really impressive would be to reproduce the Hewlett Packard historic (HP-200A) using FETs and solid state approach to the large variable cap. If my memory is correct, each section of a ganged cap (like the one shown in the photo) were about 365pF max.

http://oak.cats.ohiou.edu/~postr/bapix/HP200C.htm
You know, I actually HAD one of those, years ago! I sold it at a ham flea marker. Just hope it found a good home. :)
 
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