I figure out that the opamps in my circuit get very hot, The circuit is simple : 4 unity gain buffer using TL074 (-in=>out). The circuit has its normal electrical function but when I touch the chip surface I can feel a high temperature that is not normal to me. I have several instances of the same design on the PCB with the same behavior.
It is really strange because I moved my design on bread-board using DIP version of TL074 without any heat problem. The only difference now is that the SOIC version of TL074 is soldered on a well grounded PCB! I use +/-12 v on the rails + 100nF cermic caps close to the chip power pins.
Any difference between the DIP and SMD package of TL074?
Any Idea about the high temperature?
Smaller package... Higher temperature. Define 'high temperature' because if you can touch it without removing skin from your finger it's not hot enough to damage the electronics. "Hot" is relative.
Smaller package... Higher temperature. Define 'high temperature' because if you can touch it without removing skin from your finger it's not hot enough to damage the electronics. "Hot" is relative.
Also what loads are you driving? If you need voltage followers I presume you are driving low-ish impedance loads from a fairly high Z source.
Most op amps are unity gain stable - but that depends on what the load is. I have seen op-amps take considerable current (and hence get very hot!) on some student circuits where the op-amp was unstable (and oscillating). Some op-amps will go unstable when driving capacitive loads...
it gets very hot when use 12v n 5 amps powersupply! Try to reduce amperage and post response.. My tl072 ic would get very hot and make hum when operate but i simply added a resistor to the '+' supply and the problems were fixed.
Smaller package... Higher temperature. Define 'high temperature' because if you can touch it without removing skin from your finger it's not hot enough to damage the electronics. "Hot" is relative.
Try to reduce amperage and post response.. My tl072 ic would get very hot and make hum when operate but i simply added a resistor to the '+' supply and the problems were fixed.
I checked it with scope, there is only a 5mVp-p AC ripple at the output stages which I think is a portion of power supply ripple. it does not sound like oscillation.
How an oscillating/unstable opamp should be ? Can it easily be traced with scope?
I planned to move from SOIC package to TSSOP due to size limit of my PCB. With my experience with SOIC I think a TL074 in TSSOP package will melt my PCB.
I saw the datasheet of a Japanese (Toshiba?) copy of a TL074 where they made it "better". They made it oscillate at a high frequency which made it hot. They recalled and replaced most of them. Maybe you have a bad copy. Use an American TL074.
A TL07x will oscillate when its output directly drives the capacitance of a couple of feet or more of shielded audio cable. It is fixed by adding a 100 ohm resistor in series with the output of the circuit so that the resistor drives the cable.
hmm this is interesting, cause I have some LM555CN timers that I got that have a max supply of 16 volts, but when powered even with twelve volts, they get warm, even during normal usage. They are in dip-8 packages.