I preface this with saying that at one time, many many years ago, I had taken some EE courses. I remember only a little.
I was simulating a simple non-inverting amplifier used in a DC setting as a refresher and I noticed that depending on which model OpAmp I used, I got very different simulator results.
I was comparing the two datasheets and I don't see a significant difference.
LM324 LF412
Parameter Min / Max Min / Max
Input Offset Voltage ? / 3mV ? / 3mV
Input Bias Current ? / 100nA ? / 200pA
Input Offset Current / 30nA / 100pA
Input Common Voltage 0 / V+-1.5V -11V/ 11V
Supply Current ? / 1.2mA / 6.5mA
Output Source Current 20mA/ ? ? / ?
The LM324 and LF412 data sheets. I am using this summary as a refresher as to what all these terms mean.
The parameter that I'm not certain about is Input Common-Mode Voltage Range.
I believe, because of the "virtual short circuit approximation", that both inputs (V+, V-) are at roughly the same voltage most of the time. So I don't think this affects the simulation, but I'm not sure.
All the other parameters appear to be within range of each other (or are in the pA/nA range so I'm ignoring them).
This is the circuit I'm testing. It's attempting to amplify the Vin
voltage by 1.4 such that when Vin
is in the range 0,5V DC then Vout
is 1.4x higher in the range 0,12V DC (I'm aware that I will never reach 12V exactly).
Here is the simulation using the LM324. This is the expected output:
Vmax is orange
Vout is blue
Vin (the V+ input) is yellow
Here is the simulation using the LF412. This seems very wrong:
Vmax is orange
Vout is blue
Vin (the V+ input) is purple
alsoVin (the V- input) is yellow
Vs
is just industry standard terminology or something? I don't see it defined in the data sheet anywhere. It does explicitly define V+ and V- as the positive and negative power supply inputs. I guessVs=+/-11V
is shorthand forV+=11V, V-=-11V
? \$\endgroup\$