bwana1
Junior Member level 3
Hi all,
I'm a retired engineer who is willing to learn using NI CDS11.
As I'm used to start bottom-up I'm trying to simulate some simple circuits at first.
So I began simulating a simple op-amp follower, powered by a single supply from
-VCC to +VCC following the supply midpoint-value obtained with two 10k resistors.
The initial idea was to use it to obtain an analog ground for a battery operated equipment.
I have used TI TL08x op amps all the life long, so I was very disappointed when I saw lots
of errors coming out from simulation. At first it seemed that it wasn't allowed to put analog
ground symbol on a generic node like the op-amp output because virtual instruments gave
faulty readings, even using floating instruments as a tester. My second move was then to
stick it to the most negative potential, the battery (12V) minus. This time the circuit began to
work but behaving erratically, halting on errors that could not be recognized. I then replaced
the TL084 with a CA3130 and all worked well at first.
I made some other test with other largely used op amps and saw that these coming from 741
were more prone to simulation crash. I thought that the SPICE model was broken, and
downloaded some up to date from TI site. A visual cross inspection showed that the SPICE
models loaded were OK.
It seems to me the simulator has some bug dealing with those op-amps, can anybody please
indicate me a possible error or an alternative very common 4 x jfet op-amp building block that
works instead?
Best regards
I'm a retired engineer who is willing to learn using NI CDS11.
As I'm used to start bottom-up I'm trying to simulate some simple circuits at first.
So I began simulating a simple op-amp follower, powered by a single supply from
-VCC to +VCC following the supply midpoint-value obtained with two 10k resistors.
The initial idea was to use it to obtain an analog ground for a battery operated equipment.
I have used TI TL08x op amps all the life long, so I was very disappointed when I saw lots
of errors coming out from simulation. At first it seemed that it wasn't allowed to put analog
ground symbol on a generic node like the op-amp output because virtual instruments gave
faulty readings, even using floating instruments as a tester. My second move was then to
stick it to the most negative potential, the battery (12V) minus. This time the circuit began to
work but behaving erratically, halting on errors that could not be recognized. I then replaced
the TL084 with a CA3130 and all worked well at first.
I made some other test with other largely used op amps and saw that these coming from 741
were more prone to simulation crash. I thought that the SPICE model was broken, and
downloaded some up to date from TI site. A visual cross inspection showed that the SPICE
models loaded were OK.
It seems to me the simulator has some bug dealing with those op-amps, can anybody please
indicate me a possible error or an alternative very common 4 x jfet op-amp building block that
works instead?
Best regards