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| Does This Circuit Destroy an Op Amp |
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| eev_carl:
Hi, I pulled this schematic from "Op Amp Circuits: Simulations and Experiments" by Sid Antoch. I replicated the results with an LT Spice simulation but when I breadboarded this with a 14588, I noticed that my current protection kicked in after about a minute. Two chips seemed to respond ok initially in terms of current and voltage. However, they both started pulling in 150mA which is my power supply cap. I watched this happen to two ICS. Do I need a current limiting resistor on the V+ for this to work? I verified each of the three voltages (-10,10,5) from the power supply with a DMM. Thanks, Carl |
| T3sl4co1l:
Did you forget bypass caps? Tim |
| eev_carl:
I didn't have any on. Should I put a pair of ceramic 0.1uF ones on V+ / GND and V- / GnD? |
| T3sl4co1l:
Yes, or 10uF electrolytic, or both is even better. You should probably pay attention, to when things are getting... hot, and smelly and burned. ;) It sounds like the chip was, I assume oscillating (without an oscilloscope, it's not easy to prove), causing excess current draw, causing it to heat up. Eventually it got past maximum temp rating and failed shorted. Tim |
| capt bullshot:
Did you turn on the 5V last? If you apply a low impedance voltage source to the Op Amp inputs without the supply voltage you might damage the IC. A series resistor to the + input isn't necessary in theory, but helpful in practice (1k ... 10k should do the job here). |
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