Simulation of the VCO Circuit in Hammerhead

[nick_f]

Hi All,
I wanted to learn more about the VCO circuit of Hammerhead with a 555 and a current mirror and I've done a Spice simulation using the freeware program LTSpice.
The signal voltage is not like in the real circuit, but the result is good enough to allow me to play with changing component values and analyse the effect these changes have.
I will post here a screenshot of the waveforms at the speaker, on capacitor C22 and the signal applied on emiter of Q6.

Regards,
Nicolae

[B^C]

Gday Nicolae,

I opened the attachment, but the 555 model is missing, is this just the NE555 model from the program or a different one, if different have you got the asc model for it?

Thanks.

[Mechanic]

Hi B^C,
I just plugged in the NE555 and it seems to work fine. As far as I know(which isn't that far!) a 555 is a 555 is it not? Only the packages vary.

Nickolae,
Thanks for putting up the circuit. I am just starting to learn spice(about 5 days now) so it is good to have some circuits to experiment with.

Cheers

[nick_f]

Gday Nicolae,

I opened the attachment, but the 555 model is missing, is this just the NE555 model from the program or a different one, if different have you got the asc model for it?

Thanks.

Hi B^C,

Sorry, I haven't checked the replies to this thread. I am uploading the file for LMC555 now.
There is a library file, which has to be placed in: C:\Program Files\LTC\SwCADIII\lib\sub and the symbols for 555 and 556, which has to be placed in: C:\Program Files\LTC\SwCADIII\lib\sym

The LMC555 is the CMOS version of 555. To my knowledge, it has overall better performance than old 555. Carl actually recommends the CMOS version for 555, even if he mentioned in the list of components the NE555, which is not a CMOS. For this reason, the output level may not reach 0V and it needs to be "helped" by some 5.1kohm resistors from output to ground.

Regards,
Nicolae

[Mechanic]

Well there you go!

Hi Nicolae,
Well there you go hey, There is more depth to a 555 than I thought. Thanks for posting the info.
Cheers