Re: Oscillators in LTspice

On 10/18/24 18:38, bitrex wrote:

On 10/18/2024 12:33 PM, Cursitor Doom wrote:

Gentlemen,
>
I've never spiced an oscillator AFAICR. Do they self-start in spice
simulators (LT in particular)? IOW, did Mike Engleheart build something
into the engine which generates wideband 'background' noise, particularly
at 'power up' as it were? I'm assuming there must be some such mechanism
and if there is, it must be present by default for all schematics one
attempts to simulate and not just oscillators?

 They can be a PITA to start in LTSpice, like this old chestnut really doesn't want to run at all IME in LT but is fine on a breadboard:
 <https://upload.wikimedia.org/wikipedia/en/thumb/8/83/Forrest_Mims_hand_drawn_circuit_1983.jpg/220px-Forrest_Mims_hand_drawn_circuit_1983.jpg>

I tweaked it a bit, but the simulation below works.
Jeroen Belleman
Version 4
SHEET 1 1348 680
WIRE 0 -48 -160 -48
WIRE 160 -48 0 -48
WIRE 336 -48 160 -48
WIRE 0 16 0 -48
WIRE 160 16 160 -48
WIRE 336 80 336 -48
WIRE 160 128 160 96
WIRE 272 128 160 128
WIRE -160 176 -160 -48
WIRE 160 176 160 128
WIRE 0 224 0 96
WIRE 64 224 0 224
WIRE 96 224 64 224
WIRE -160 288 -160 256
WIRE 64 304 64 224
WIRE 96 304 64 304
WIRE 208 304 96 304
WIRE 336 304 336 176
WIRE 336 304 272 304
WIRE 384 304 336 304
WIRE 416 304 384 304
WIRE 0 320 0 224
WIRE 336 352 336 304
WIRE 0 464 0 400
WIRE 160 464 160 272
WIRE 336 464 336 432
FLAG 336 464 0
FLAG 160 464 0
FLAG 0 464 0
FLAG -160 288 0
FLAG 384 304 out
FLAG 96 304 b
SYMBOL npn 96 176 R0
SYMATTR InstName Q1
SYMATTR Value 2N3904
SYMBOL res 144 0 R0
SYMATTR InstName R3
SYMATTR Value 1k
SYMBOL pnp 272 176 M180
SYMATTR InstName Q2
SYMATTR Value 2N3906
SYMBOL cap 272 288 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C1
SYMATTR Value 22µ
SYMBOL res 320 336 R0
SYMATTR InstName RL
SYMATTR Value 30
SYMBOL res -16 304 R0
SYMATTR InstName R2
SYMATTR Value 56k
SYMBOL res -16 0 R0
SYMATTR InstName R1
SYMATTR Value 220k
SYMBOL voltage -160 160 R0
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V1
SYMATTR Value PWL(0 0 1u 9)
TEXT -192 400 Left 2 !.tran 10
TEXT -192 448 Left 2 !.ic v(b)=0
TEXT 496 0 Left 2 ;Flasher, according to Forrest Mims.
TEXT 496 48 Left 2 ;Jeroen Belleman - 20241018