I recently made a triangular waveform generator circuit using LM324 op amp. But the output of the generator had some sort of periodic spikes in it. However I was able to suppress the spikes by lowering the load resistor (<=1Kohm, 680ohm completely killed the spikes). What can be the reason for that? My first guess was that there may be a pole somewhere in the feedback loop due to parasitic impedance and the lower load resistor has compensated for that.
I tried the same circuit using TL084 op amp which has JFET inputs. This time the spikes were never there even when the load resistor was not connected! So if there was a pole in the feedback loop, then the spikes should have appeared in this circuit also. I am wondering what can be the REAL cause for the spikes and how did the load resistor kill it? I really appreciate some help from someone with an experience in this field.
Note: I used a solder-less breadboard for constructing the circuit
Schematic:
simulate this circuit – Schematic created using CircuitLab
Waveform (LM324) 
Waveform (TL084): 
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