Re: The not-all-that-low distortion sine wave oscillator in a faster simulating version

On 18/12/2024 5:16 pm, bitrex wrote:

On 12/17/2024 10:49 PM, Bill Sloman wrote:

I've been playing with the circuit, and have got rid of one op amp, which made the simulation run much faster, but didn't help the distortion performance.
>
Swapping the LT1115 for the LME49710 speeded up the simulation a bit more, but didn't make any difference to the distortion either. A few of the ferrite beads have gone too.

 It seems to like to squeg for me (LTSpice 17.0.37)
 <https://imgur.com/a/6uqsw1H>

I've seen that happen, but only when the one of the connections has come unstuck. The route through WordPad to here and on to your own .asc file can screw up the schematic.
The amplitude control feedback loop - through the four-pole maximally flat low pass filter around U6 and U7 through the integrator around U5 does include the 68k resistor at R10 to provide enough phase lead to keep it stable.
I plot V(out) and the control voltage V(fet-gate), and V(fet-gate) starts off at 0V and drops below -3.862V within 5msec after which V(out) starts building up. The amplitude control system system kicks in at 20msec and by 41msec has got V(fet-gate) back to -3.862V where V(out) starts to fall back, and eventually undershoots, but the ringing is damped, and the system is stable after about 0.5 sec.
Post the .asc file you ran.
--
Bill Sloman, Sydney