Some of it is invisible at the moment we will be able to make it visible when needed. It's very unlikely that the engineers (or interns) who developed the model optimized it or verified its accuracy for simulating operating conditions outside the datasheet limits.6 However, there is considerably more information about the layout than what we see here.
Again this could easily lead to a drop in gain.Īs mentioned before, you shouldn't trust the simulation model to be accurate under these conditions - the simulator is meant to tell you how the circuit will behave under typical operating conditions. It's also possible that at some point the bias point of some internal nodes in the circuit get out of whack, breaking the connection from one stage to another. At some point, the bias point you chose for your simulation went out of the common mode range for that supply voltage, and the amplifier gain dropped. Probably, as the supply voltage drops, the input common mode range changes. Now, what is going on in your simulation?ĭata handling from simulations of a class of Op Amp (LMC6482) in NI Multisim showed that open-loop gain drops drastically when a certain supply voltage is reached (from high to low voltages) as is expected, but it continues decreasing, reaching almost zero when supply voltage is not zero yet. So you can't trust that your simulation results are reflecting the real behavior of these op-amps. You also shouldn't expect the simulation model to be accurate when the operating parameters (like supply voltage) are outside the specified ranges. There is nothing guaranteed about its performance under these conditions. You should not operate your op-amp with a lower supply voltage than its datasheet specifies. Well-designed op-amp circuits will give good results as long as the gain is "high enough" and won't depend on the exact value of the gain. Simulators won't tell you about this variation, they'll just give you the performance of a "typical" device. It might be dramatically different from device to device. Gain of an op-amp is not well controlled. If simulation data is not trustworthy at supply voltage lower than recommended operation conditions, what could be the best way to approach to transition between the Op Amp operating from active to passive?įirst, your question is misguided for at least two reasons: I attached a plot showing the numerical data obtained in NI Multisim. Is it physically possible to get open-loop gain values that low? Can saturation voltage levels play a part in this situation by decreasing too much while open-loop gain remains at low but not-less-than-unity value? Is there a way of relating other Op Amp parameters to obtain the open loop gain as a function of supply voltage? Data handling from simulations of a class of Op Amp (LMC6482) in NI Multisim showed that open-loop gain drops drastically when a certain supply voltage is reached (from high to low voltages) as is expected, but it continues decreasing, reaching almost zero when supply voltage is not zero yet. Now, I'm struggling with relating the open-loop gain to supply voltage, especially at low values of the latter. One of my main variables to watch is supply voltage. I'm new in electrical engineering (since I'm a chemical engineer) but I've been working on system dynamics through simulation of a DC circuit that involves Op Amps.