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negative voltage rails
- Thread starter Homebrew1964
- Start date
I got my results from a no load application and was very happy, i didn't try loading the output so i don't know what results i would actually got in a real world situation. If i ever build thew circuit again i will check that.
Yes that makes a difference. Was the chip you used a 741 or the OP07?
An LM741 as in the schematic in my initial post #1
The schematic in post one show both LM741 and OP07.
sorry....the program won't allow me to delete the OPO7 label....i used the LM741
Your output was loaded with 20 kΩ. The opamp neither knows nor cares whether what it is driving is what you would think of as a "load" or part of the feedback network. It just knows that in order to establish the desired voltage, it must produce a certain current.
How are you getting the "LM741" onto the schematic? If you are putting it on as just a piece of text, that's not the best way to do it. You want to change the part's device model. But that requires that you have the necessary model definition if you want to actually run a simulation.
There is no spec at ±4.5 V. The 741 wasn't intended to be run from such low rails. The normal rails were ±15 V and that's what most of the specs where characterized at. But output voltage swing relative to the rails tends to be pretty insensitive to what the rails actually are since the device behavior is primarily being determined by circuitry operating near the rail in question.
I just typed in op and the LM741 symbol popped up so i used that.
When I type op, I get the OP07 (since that's the first part whose name starts with 'op'). The stock LTSPICE install doesn't have an LM741 model.
Yes thats why i used the first op amp symbol i could find...typing in "LM741" doesn't give me a good useable result
In fact LTSpice doesn't recognize every component, I don't know why though since most components are still in use.
If it recognized every component still in use, you would need a much bigger hard drive to install it. Plus, new components get introduced all the time.
The key point is that LT stands for Linear Technology and LTspice (that's the official capitalization, which I often mess up because SPICE is, itself, a proper acronym) was developed as a tool for engineers (initially, their internal engineers) to be able to better design analog integrated circuits, particularly switching regulators. Later, they released it for free to encourage engineers to design systems with Linear Technology components, so they had no motive to include device models for competing components or components not commonly used in designing the kinds of circuits their parts were intended for.
Over time, LT was acquired by Analog Devices, who also acquired companies such as Maxim. So many of the parts produced by those companies are now included.
