Maximum Output Voltage of a LF411 inverting Op-Amp

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SUMMARY

The maximum output voltage of the LF411 inverting op-amp is constrained by its supply rails, which are typically ±15V to ±18V. For a 1V triangle wave input, the output voltage can reach ±10V, while for a 3V input, the output can theoretically reach ±30V peak-to-peak with a gain of 10. However, due to the op-amp's inability to approach its supply rails closely, the effective output voltage is limited to approximately ±15V. This limitation necessitates careful consideration of input voltage levels to ensure the output remains within the op-amp's operational range.

PREREQUISITES
  • Understanding of op-amp gain calculations
  • Familiarity with the LF411 op-amp specifications
  • Knowledge of voltage supply limitations in op-amps
  • Basic circuit analysis skills
NEXT STEPS
  • Review the LF411 datasheet for detailed electrical characteristics
  • Learn about op-amp output swing limitations
  • Study the impact of load resistance on op-amp performance
  • Explore practical applications of op-amps in signal processing
USEFUL FOR

Electrical engineers, students studying circuit design, and anyone involved in analog electronics who needs to understand op-amp output limitations and gain calculations.

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Homework Statement


Prelab material, I know how to solve for the gain and vout on a circuit. But reading the actual manual of a op-amp is confusing and I just want to make sure I'm correct. The initial input voltage will be a 1V triangle wave. Then later we increase the voltage to 3V. R1 is 1K and R2 is 10k.Here is the manual:
https://c8ad3030-a-62cb3a1a-s-sites.googlegroups.com/site/ece35fall2013/lab-files/LF411.pdf?attachauth=ANoY7cp7jf3VzZkloe5hCZF3-adLMzKwTZs5blfi3Rp2Zg8oP_9M89hjVq6ird126VkCh9O_71xGbeXVGIlt0AidR7GaLnaLpqTz8MdA1A50gsFOVQBS2uVLscOtqFdcksXPXY5H3O_HpAPDh5VQ0FQK4YC7Y4tyMNoHeZnNjPM02zItNjttYD7rhhp6g1MO_Wk1kdJ7gepgBaOSsO9uz3-uz7LvdPP7-gmbbBcnyMkwOeEK2bMkHCU%3D&attredirects=0


Homework Equations


Vout/Vin = -R2/R1


The Attempt at a Solution


I know the output voltage will be ±10V for the 1V triangle wave. But for the 3v, if I am reading correctly, Vs = ±15 at the Vo tab under DC characteristics, which means the output voltage will be ±18 even though our gain is supposed to be a factor of 10. Is this correct? Thanks
 
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Op amp output voltage is limited by the supply rails ... that's your voltage source.

So if the max rating on the rails is +/-18 V, you can never exceed that, regardless of the amplification. Looking at the spec sheet I am not sure what the actual limits are ... about 15 V from a quick look, which is less than the max at the rails.

So you want to limit your Vin to values which generate a Vout which is possible with the maximum voltages supported.
 
Many OP amps can't get within 3V of their rails so a general rule would be 18V-3V = 15V. That appears to be the case for this op amp. Interesting to consider what they use in 3V and 5V portable devices.

Is the triangle wave 3V peak to peak? If so then with a gain of 10 the output will be 30V peak to peak. Half of that is 15V so you might just get away with it on +/- 18V supplies.

Take a look at the circuit on page 9 of the data sheet. the reason the output cannot swing higher is the voltage drop across this path 300R -> Q1 -> 33R -> Q3 -> Q6 -10R
 

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