Maximum supply voltage to a TL072 opamp

Frequently asked questions regarding powering your pedal.

Maximum supply voltage to a TL072 opamp

Postby richard44 » 13 Jun 2013, 12:15

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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Re: Maximum supply voltage to a TL072 opamp

Postby FiveseveN » 13 Jun 2013, 13:17

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.
Ignorance more frequently begets confidence than does knowledge. (Charles Darwin)

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