Hello all
I am attempting to complete an assignment, which asks for a measurement of the Slew Rate of the LM741 and LF356 Operational Amplifiers. This is being facilitated through the use of Multism v11, in which I have constructed a Unity Gain circuit with an LM741CH, which is the Op-Amp that I wish to focus on for the purposes of this question.
The input signal is a 2V square wave. I have tried to make Slew Rate calculations based off the signal displayed by the Multisim virtual oscilliscope, at many different input frequencies (10Hz to 10MHz), but I seem to be getting the wrong answer consistently.
The National Instruments Datasheet concerning the LM741CH, specifies a typical slew rate of 0.5V/us, from a Unity Gain configuration. I am assuming that this reading can be obtained without placing a particular kind of load at the Op-Amp's output, as the Datasheet does not specify one.
Now, as an example- the Input Voltage is 2V, and the Input Frequency is 100KHz. Observing the Output Square Wave, some Slewing is clearly evident. So, using the Oscilliscope, I determine that deltaV is 2V, and deltaT is 701.493nS. Thus the Slew Rate can be calculated thus:
SR = deltaV / deltaT
= 2 / 701.493E-9
= 2851061.949
= 2.8V/us
The result above is of course a substantial deviation from the Datasheet's typical value, and this error seems to be translated accross the whole range of frequencies and input voltages. I realise that it is customary to measure the slew rate between 10% and 90% of the Rise or Fall Time, but I would like to get a Slew Rate Value at least approaching the typical one before doing that.
I am at my wit's end, and I was wondering weather anyone on this fantastic Electronics Resource might be able to help me work out where I am going wrong.
The attachment contains an image of the circuit and waveform for the calculation above.
Looking forward to hearing some suggestions.
Many Thanks.
Adam.
I am attempting to complete an assignment, which asks for a measurement of the Slew Rate of the LM741 and LF356 Operational Amplifiers. This is being facilitated through the use of Multism v11, in which I have constructed a Unity Gain circuit with an LM741CH, which is the Op-Amp that I wish to focus on for the purposes of this question.
The input signal is a 2V square wave. I have tried to make Slew Rate calculations based off the signal displayed by the Multisim virtual oscilliscope, at many different input frequencies (10Hz to 10MHz), but I seem to be getting the wrong answer consistently.
The National Instruments Datasheet concerning the LM741CH, specifies a typical slew rate of 0.5V/us, from a Unity Gain configuration. I am assuming that this reading can be obtained without placing a particular kind of load at the Op-Amp's output, as the Datasheet does not specify one.
Now, as an example- the Input Voltage is 2V, and the Input Frequency is 100KHz. Observing the Output Square Wave, some Slewing is clearly evident. So, using the Oscilliscope, I determine that deltaV is 2V, and deltaT is 701.493nS. Thus the Slew Rate can be calculated thus:
SR = deltaV / deltaT
= 2 / 701.493E-9
= 2851061.949
= 2.8V/us
The result above is of course a substantial deviation from the Datasheet's typical value, and this error seems to be translated accross the whole range of frequencies and input voltages. I realise that it is customary to measure the slew rate between 10% and 90% of the Rise or Fall Time, but I would like to get a Slew Rate Value at least approaching the typical one before doing that.
I am at my wit's end, and I was wondering weather anyone on this fantastic Electronics Resource might be able to help me work out where I am going wrong.
The attachment contains an image of the circuit and waveform for the calculation above.
Looking forward to hearing some suggestions.
Many Thanks.
Adam.
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