Current comsumption question: what uses the most current?

tysseng · Joined: Apr 14, 2013 Posts: 13 Location: Norway

Hi!

I have built a waveshaper based on the YuSynth VCO. All components are SMD, and it has three TL074 and one TL072 op amps.

The op amp ICs run fairly hot, I can touch them but they are warm. I measured the current draw from each rail and they are around 27mA per rail. Comparing this to what is listed for the YuSynth VCO (27 and 28mA) it does seem to be ok.

But this got me wondering - what parts of the circuit draws the most current? The VCO has 10 op amps and one comparator. My waveshaper has 18 opamps.

Comparing that to the YuSynth wavefolder which has 6 op amps but only uses 5 and 3 mA, or the Min/Max which has 10 op amps but only uses 3.5 and 3.5 mA, it is clear that the number of op amps at least does not decide the current consumption.

So what does? What decides how much current an op amp uses?

blue hell · Posted: Mon Jun 22, 2020 5:26 am Post subject:

There are two components for that .. the no-load supply current (of about 1.5 mA / op amp for the TL-07x) and the current flowing from it's output into the load .. the latter also depending on the voltage swing at the output ... so that depends on the actual circuit.

BTW . the maximum internal operating temperature for the op amps used is about 150C .. so .. as long as a wet finger put on it doesnt hiss (on a very hot day) Laughing

... a bit of warm to the touch is fine.