Maximum supply voltage to a TL072 opamp

Frequently asked questions regarding powering your pedal.
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richard44
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Post by richard44 »

I was hoping someone here could clarify a question about the maximum possible supply voltage to an opamp in a single supply design.

The question:
Via an 18V wall wart brick, or two combined 9V supplies from a Voodoo Power Supply, can I safely supply +18V in a *single-supply* design to the power rails of a TL071 or TL072 op amp?

The application is any homemade distortion / boost / overdrive pedals that utilizes the above opamp. All the capacitors have at least a 35v tolerance, so this question is not about capacitors, but specifically about the op amp in the circuit.

The opamp datasheet gives the following specs, and I need to really understand how to interpret this data:

Supply voltage: Vcc+ = +18V / Vcc- = -18V
Differential Input voltage: +/- 30V
Input voltage: +/- 15V

So in my single-supply design, I would have 0v to 18V, with a Vref (or Vbias) of 9V. This setup is somewhat standard in stompboxes. Just to be clear, I am NOT using a dual (aka bipolar) supply which would spread the 18 volts with a + 9V above zero, and -9V below zero.

I can interpret the above listed specs in two ways. Depending on which is correct, one says I am totally safe, the other says I am near the danger point:

1) If the opamp can tolerate the range of +/- 18V (or 36V total swing), and does not care if that voltage swings between -18V and + 18V, or let's say 0V and 36V, then my running the pedal between 0V and 18V is not even near the limit and I can safely do what I want to;

or,

2) If the opamp can tolerate the range of +/- 18V with its swing above and below zero, but cannot go above +18V because the +18V is an upper limit (above which damage would occur to it), then running my pedal 0 to 18V will be right at the border of damaging it.

I hope this is clearly stated and that someone can share some insights about interpreting the datasheet specs. Thanks.

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FiveseveN
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Post by FiveseveN »

The amplifier does not "know" where "0" is in your second example. You can power it with Vcc+ = +1036V and Vcc- = +1000V if you so desire, as long as you bias it within its range (thus "telling" it where the reference voltage is). So your first reading is correct.
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