#LM 741 GENERATOR#

Yes, you should have an off-set due the DC Op Amp non-idealities being amplified by the DC 'Closed Loop Gain', adding a 'coupling' capacitor (between the Schmit Trigger Oscillator and R4) has two results: R6 is meant to aid with this issue and it should be R6 = R4||R5, however, this method it is not always effective because it depends on the Op Amp.įor more details on Input Bias Cancelation Resistors, check this. current coming and going out of the Op Amp input pins). Increasing R5 to 100 kOhm (that is 100⋅R4), puts 'fC' at a lower frequency, increasing the range of frequencies for which your circuit will behave as a good integrator.Īs I mentioned before, one of the disadventages of the non-ideal Op Amp for an Integrator is that the 'Bias Current' (i.e. 'fC' and 'fL' are too close to each other). R5 is too small, that means that you will have an very small area where your circuit will behave as a good integrator (i.e. Remember that a Capacitor is a 'Frequency Controlled Resistor' and having C2 = 1 uF, at 1 kHz looks like a ~160 Ohm Resistor, that means that if R5 = 1 kOhm then 'fL' < 1 kHz, so your signal will get attenuated significantly.ĭecreasing C2 to somewhere between 100 nF and 220 nF should be a good starting point to increase 'fL' enough.

think of a Capacitor as a Variable Resistor (or Frequency Controlled Resistor) that decreases under two conditions: Your first problem is that C2 is too big. In other words should be in the yellow shaded area in the figure above. This is important because the frequency of the signal that you want to integrate should be above 'fC' but before reaching 'fL'. Note: having R5 being 100 times bigger than R4 allows for enough separation between 'fC' and 'fL' to allow for the circuit to behave as a 'good' integrator. You can use the following definition to determine the Output Voltage of your comparator, given the current state: The Texas Instruments LM741 Datasheet specs between ☑0 V and ☑3 V for a 2 kOhm load, so as the other commenters have suggested you might want to increase the Integrator's resistor values.įor more details on Output Limitations check this. Note that as other commenters have noted this depends on your load, which in your current set up is around 1 kOhm. This is important because you might not be able to achieve an output of ☑5 V due to the Op Amp Output 'Voltage Swing' Limitations. Your output will look similar to this at the beginning: Ideally it would be amplified forever, however the Op Amp has Output Limitations which causes the output to saturate at VCC or a voltage close to it, depending on the Op Amp.

#LM 741 GENERATOR#

There is two components to your the generator ☑5 V Triangle Wave Generator you are trying to generate, the first stage is the Schmitt Trigger Oscillator then the Integrator so I think it would be appropriate to discuss them separately first.įirst, let's discuss how it operates to aid the understanding let's refer to the figure below.Īn excitation - namely the intrinsic noise in your system will go into the Op Amp, and will be amplified by the 'Closed Loop Gain' which approaches the 'Open Loop Gain' much like it does in an basic Op Amp integrator circuit. The square wave output is still determined by the saturation of the opamp as before, an opamp with rail to rail output will get very close to the supply rails. The second stage is configured as an integrator and will produce a triangular wave with linear slopes. The first stage is arranged as a schmitt trigger to detect when the output of the second stage reaches voltages determined by resistors R1 and R2. It still uses two opamps and only needs one capacitor to set the timing. This configuration should give better results: The 741 os a very ancient opamp and is not as good as more modern ones - as Peter mentioned the output cannot get closer than ~2.5v to the rail. You can use something in the range 10k-100k.ģ) The actual amplitude of the output will be limited by the opamp. 1) The second stage will generate an exponential rather than a triangle.Ģ) The resistor values for feedback on the second stage are much too low - the amplitude may be limited by the output current capability of the 741.

Lm 741