Helmut Sennewald wrote:
Hello Anthony,

1.
Please set the following option to sitch off data
reduction/compression in the result file..

.options plotwinsize=0

2.
You have to set a small maximum timestep in the .TRAN line too.
Maybe a value of 0.01*Period of oscillation if you hunt for very low
distortion.


Can you send me your file (.asc-file and model-file?) to check it?

In alt.binaries.schematics.electronic I have posted the schematic, the
asc-file and an oscilloscope screen shot from an actual circuit. Here is
the asc-file contents:

Version 4
SHEET 1 880 708
WIRE -704 -96 -784 -96
WIRE -400 -96 -704 -96
WIRE -224 -96 -400 -96
WIRE -704 -16 -704 -96
WIRE -400 -16 -400 -96
WIRE -224 32 -224 -96
WIRE -544 80 -592 80
WIRE -400 80 -400 64
WIRE -400 80 -464 80
WIRE -288 80 -400 80
WIRE -592 128 -592 80
WIRE -400 144 -400 80
WIRE -784 160 -784 -96
WIRE -400 240 -400 208
WIRE -224 240 -224 128
WIRE -224 240 -400 240
WIRE -80 240 -224 240
WIRE 48 240 -16 240
WIRE -784 272 -784 240
WIRE -704 272 -704 48
WIRE -592 272 -592 208
WIRE -400 272 -400 240
WIRE -224 288 -224 240
WIRE -592 384 -592 336
WIRE -400 384 -400 336
WIRE -400 384 -592 384
WIRE -224 384 -224 368
WIRE -224 384 -400 384
WIRE -400 448 -400 384
FLAG -784 272 0
FLAG -400 448 0
FLAG -704 272 0
FLAG 48 320 0
SYMBOL voltage -784 144 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value 5.8
SYMBOL res -416 -32 R0
SYMATTR InstName R3
SYMATTR Value 100k
SYMBOL npn -288 32 R0
SYMATTR InstName Q3
SYMATTR Value 2N3904
SYMBOL cap -416 144 R0
SYMATTR InstName C1
SYMATTR Value .01µ
SYMBOL res -240 272 R0
SYMATTR InstName R7
SYMATTR Value 1k
SYMBOL cap -416 272 R0
SYMATTR InstName C2
SYMATTR Value 500p
SYMBOL ind -608 112 R0
SYMATTR InstName L1
SYMATTR Value 20µ
SYMATTR SpiceLine Rser=.1
SYMBOL cap -608 272 R0
SYMATTR InstName C3
SYMATTR Value 200p
SYMBOL cap -16 224 R90
WINDOW 0 0 32 VBottom 0
WINDOW 3 32 32 VTop 0
SYMATTR InstName C4
SYMATTR Value 270p
SYMBOL res -448 64 R90
WINDOW 0 0 56 VBottom 0
WINDOW 3 32 56 VTop 0
SYMATTR InstName R1
SYMATTR Value .001
SYMBOL cap -720 -16 R0
SYMATTR InstName C5
SYMATTR Value 10µ
SYMBOL res 32 224 R0
SYMATTR InstName R2
SYMATTR Value 10000k
TEXT -792 360 Left 0 !.tran 50uS

Thank you for your time.


Best regards,
Helmut




"Anthony Fremont" schrieb im Newsbeitrag
...
Pictures available in ABSE

The top trace (yellow) is taken between C4 and R2. The bottom trace
(cyan)
is taken at the base of the transistor. There is a switchercad
file, but the simulation will show allot of distortion that really
isn't present in the prototype circuit, because of lots of circuit
capactance I suspect. R1
was something I was playing with to try and tame the voltage across
L1/C3 being applied to the base.


Hello all,

I was tinkering with this LC oscillator (Colpitts/Clapp) this
weekend. I arrived at the values of C1 and C2 empirically after
starting with a crystal
oscillator circuit. The values in the original circuit created a
horrid waveform that looked allot like the simulation. After much
tinkering around
and simulating, I come to the conclusion that getting a perfect
waveform is
nearly impossible, especially with big swing. It seems that the
transistor
likes to take a bite out of the right half of the peak of the wave.

What is the secret to beautiful waveforms? Do I need another LC
resonator on the output to fix it up? I mean, I'm getting a pretty
nice wave now, but
there is still some distortion that you can just see at the top of
the peaks
on the yellow trace.

How do you control the peak voltages of an LC resonattor without
mangling the waveform? The waveform at the junction of L1/C3 is of
course quite beautiful, how do I get it from there to the output? ;-) I
realize that I will need a buffer stage(s) before I can make any
real use
of the signal, but I want the input to the buffer to be as perfect as
possible.

Thanks :-)