Re: An actual circuit

"bitrex" <user@example.net> wrote in message
news:6650d62f$0$2363134$882e4bbb@reader.netnews.com...

On 5/24/2024 2:00 PM, bitrex wrote:
>

Yes, it is mysterious. Set both drain resistors to 3.3K and zoom way
up on the two source voltages for the first 20 seconds.
>
LT Spice may have some hidden asymmetry. It has to do math
sequentially, maybe.
>
In real life, parts will be plenty asymmetric. Especially jfets.
>

>
There are bunch of variants of this circuit, I call it the "Forest Mims
Oscillator" cuz in one of his radio shack circuit books was where I first
remember seeing it as a teenager.

>
I'm pretty sure he didn't invent it though and that I've seen it in books
from the 60s also, it was probably invented about 5 minutes after the PNP.

Rufus P Turner's FET circuits is probably where I got the doing it with FETs
idea from.
It's on page 50 and easy to find a pdf.
It also says the RC circuit should matched to within 1% but not sure why.

I've not previously seen it with source resistors.
The idea of not connecting the sources to ground came about because I didn't
want the LED drive to affect the RC circuit.
So in my teens I just connected the source directly to the transistor base
with no other component and put the LED current limiting in the collector
circuit.