Upon re-examination of the question asked, I now believe the question was "How do you calculate or predict the voltage at which an inverting opamp stage will saturate?".Hello,
How do you calculate when a inveting op amp saturates? Thanks
ORa. How do you calculate the input voltage that will result in saturating/clipping the output signal?
If the question is "a." thenb. How do you calculate the voltage at which the output will clip?
You might want to think about that a little more. Remember that output current limiting is generally an instantaneous phenomenon. Suppose you had an op amp connected to +/- supplies, +/-50mA current limiting, and a 100 ohm load to GND. With the output signal at the zero crossing, no current flows. At 100mV output, 1mA flows, so no current limiting. At 1V output, the current is 10mA. Still no limiting. At 5V output, the output has reached its maximum current capability. If it tries to go to 6V, or 7V, etc., the output will be limited to 5V. This will cause severe distortion.Output current limitation should not distort the waveform. You would only see a waveform across the load that would correspond to the current across it:
Vcc = 15, RL= 100Ω, Vo = 10V, Io(max) = 50 mA would show 5V across the load. If it was a sine wave, it should not show any signs of distortion just not the amplitude expected.
Clipping, headroom issues, saturation are all the same. It is not a current limitation due to the load rather the output stage limits imposed by the supply voltage.
Look at the datasheet, or test the opamp, and find the maximum positive and negative voltage swings (which are often different magnitudes) for the given supply voltages. Use the gain and the input amplitude to calculate whether or not the opamp will try to go past its available voltage swing range.Hello,
How do you calculate when a inveting op amp saturates? Thanks
Very true. Thanks for the correction.You might want to think about that a little more. Remember that output current limiting is generally an instantaneous phenomenon. Suppose you had an op amp connected to +/- supplies, +/-50mA current limiting, and a 100 ohm load to GND. With the output signal at the zero crossing, no current flows. At 100mV output, 1mA flows, so no current limiting. At 1V output, the current is 10mA. Still no limiting. At 5V output, the output has reached its maximum current capability. If it tries to go to 6V, or 7V, etc., the output will be limited to 5V. This will cause severe distortion.